Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Stridulation and its significance in the waterbug genus Cenocorixa Jansson, Antti Risto Ilmari 1971

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1971_A1 J35.pdf [ 13.57MB ]
Metadata
JSON: 831-1.0101890.json
JSON-LD: 831-1.0101890-ld.json
RDF/XML (Pretty): 831-1.0101890-rdf.xml
RDF/JSON: 831-1.0101890-rdf.json
Turtle: 831-1.0101890-turtle.txt
N-Triples: 831-1.0101890-rdf-ntriples.txt
Original Record: 831-1.0101890-source.json
Full Text
831-1.0101890-fulltext.txt
Citation
831-1.0101890.ris

Full Text

STRIDULATION AND ITS SIGNIFICANCE IN THE WATERBUG GENUS CENOCORIXA  by ANTTI RISTO ILMARI JANSSON B . S c , U n i v e r s i t y of H e l s i n k i , 1 9 6 4 M.Sc., U n i v e r s i t y o f H e l s i n k i , 1 9 6 5 L i e . P h i l . , U n i v e r s i t y of H e l s i n k i , 1 9 6 8  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n t h e Department of Zoology  We a c c e p t t h i s t h e s i s as conforming t o t h e required standard  THE UNIVERSITY OF BRITISH COLUMBIA January, 1 9 7 1  In  presenting this  thesis  an advanced degree at the L i b r a r y I  further  fulfilment  of  the  requirements  the U n i v e r s i t y of B r i t i s h Columbia, I agree  s h a l l make i t  agree  in p a r t i a l  freely  available  for  that permission for extensive copying o f  of  this  representatives. thesis for  It  financial  i s understood that g a i n s h a l l not  written permission.  Department  of  Zoology  The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada  Date  2 Feb.  1971  that  r e f e r e n c e and s t u d y . this  thesis  f o r s c h o l a r l y purposes may be granted by the Head of my Department by h i s  for  or  copying or p u b l i c a t i o n  be allowed without my  i STRIDULATION AND ITS SIGNIFICANCE IN THE WATERBUG GENUS CENOCORIXA Abstract S t r i d u l a t i o n i n t h e waterbug genus C e n o c o r i x a was s t u d i e d i n t h e f i e l d and e x p e r i m e n t a l l y  i n the laboratory.  I t was shown t h a t both males and females s t r i d u l a t e . The s t r i d u l a t o r y s i g n a l s , analysed  by use o f a sound  graph, were shown t o be s p e c i e s and sex s p e c i f i c , i n temporal p a t t e r n of pulses, pulse r a t e , pulse and  spectrodiffering structure,  s i g n a l length. I t was shown t h a t t h e annual rhythm o f s t r i d u l a t i o n i n  both male and female i s c o r r e l a t e d w i t h s e x u a l  maturity.  Males w i l l s p o n t a n e o u s l y s t r i d u l a t e when t h e r e i s mature sperm i n t h e t e s t e s , and t h i s occurs i n s p r i n g , e a r l y summer, and l a t e f a l l .  Females do not s t r i d u l a t e s p o n t a n e o u s l y , but  can be i n d u c e d t o s t r i d u l a t e when t h e y have c h o r i o n a t e d  eggs  i n t h e l a t e r a l o v i d u c t s , but no sperm i n t h e r e c e p t a c u l u m seminis;  t h e y a r e s e x u a l l y mature o n l y i n t h e s p r i n g and  e a r l y summer. S t r i d u l a t i o n was shown t o be i m p o r t a n t i n b e h a v i o r l e a d i n g t o s u c c e s s f u l c o p u l a t i o n . Male s t r i d u l a t i o n  functions  as a c a l l i n g s i g n a l f a c i l i t a t i n g p a i r - f o r m a t i o n by a t t r a c t i n g c o n s p e c i f i c f e m a l e s , and as an a g o n i s t i c s i g n a l s e r v i n g t o space out i n d i v i d u a l s . Males w i l l answer almost any s t r i d u l a t o r y s i g n a l , but o n l y c a l l s from a c o n s p e c i f i c female i n i t i a t e searching  behavior.  R e c e p t i v e females respond t o  s t r i d u l a t o r y s t i m u l i from c o n s p e c i f i c males by s t r i d u l a t i n g , and  s u c c e s s f u l c o p u l a t i o n s were observed o n l y when preceded  ii by such s i g n a l r e c o g n i t i o n ; female s t r i d u l a t i o n f u n c t i o n s as an agreement s i g n a l . S t r i d u l a t i o n s e r v e s as a p r e m a t i n g i s o l a t i n g i n C e n o c o r i x a . However, i t i s n o t t h e o n l y  mechanism  isolating  mechanism, but i s r e i n f o r c e d by g e o g r a p h i c and e c o l o g i c a l i s o l a t i o n i n a number of c a s e s . The C o r i x i d a e , s i n c e t h e y m o s t l y have o n l y a s i n g l e s t r i d u l a t o r y s i g n a l t h a t can f u n c t i o n i n a t l e a s t two contexts,  are considered  to represent  a p r i m i t i v e stage  i n e v o l u t i o n o f s t r i d u l a t o r y s i g n a l s : a stage i n w h i c h f u n c t i o n a l d i v e r s i f i c a t i o n of s i g n a l s i s j u s t e v o l v i n g .  iii TABLE OF  CONTENTS  Page  ABSTRACT TABLE OF  i CONTENTS  LIST OF  TABLES  LIST OF  FIGURES  i i i v vi  ACKNOWLEDGEMENTS  xi  I . INTRODUCTION I I . MATERIAL AND  1 METHODS  1 . Sampling and  h a n d l i n g of specimens  9  2. L i f e c y c l e  10  3. S t r i d u l a t i o n  13  4.  19  Behavior  I I I . RESULTS 1. Mechanism of sound p r o d u c t i o n and of the s t r i d u l a t o r y apparatus  morphology 23  2. A u d i o s p e c t r o g r a p h i c a n a l y s i s of the ulatory signals a) G e n e r a l b) D e s c r i p t i o n of the s i g n a l s  strid-  29 29 32  c) E f f e c t of temperature on s t r i d u l a t i o n . 4 3 d) Sounds produced as byproduct of c l e a n i n g movements 6l 3. L i f e c y c l e , annual rhythm of s t r i d u l a t i o n , and gonad development a) L i f e c y c l e . b) Gonad development c) A n n u a l rhythm of s t r i d u l a t i o n d) M i s c e l l a n e o u s o b s e r v a t i o n s on s p e c i e s and l o c a l i t i e s 4. D i e l p e r i o d i c i t y activity 5.  of the  other  stridulating  B e h a v i o r a l r o l e of s t r i d u l a t i o n  63 63 76 89 93 96 104  iv a) Male and female response t o s t r i d u l a t o r y s i g n a l s and some o t h e r s t i m uli 104 b) M a t i n g i n C. b i f i d a c) S p e c i f i c d i f f e r e n c e s behavior  114 i n t h e mating  d) S p e c i e s r e c o g n i t i o n 6 . Geographic d i s t r i b u t i o n and notes on e c o l o g y and h a b i t a t s o f t h e s p e c i e s a) Data on d i s t r i b u t i o n and notes on ecology b) Notes on e c o l o g i c a l i s o l a t i o n i n sympatric s i t u a t i o n s  118 126 135 135 144  IV. DISCUSSION 1 . Mechanism o f sound p r o d u c t i o n and a n a l y s i s of t h e s i g n a l s 147 2 . L i f e c y c l e , s e x u a l m a t u r a t i o n , and s t r i d ulation 159 3. S t r i d u l a t o r y behavior 4.  171  Evolutionary s i g n i f i c a n c e of s t r i d u l a t i o n i n t h e genus C e n o c o r i x a . l 8  l  5 . E v o l u t i o n and s t r i d u l a t i o n i n C o r i x i d a e . . . 1 8 8 V. SUMMARY V I . LITERATURE CITED  198 200  APPENDIX I . SYSTEMATIC NOTES AND NEW SYNONYMY IN THE GENUS CENOCORIXA  207  APPENDIX I I . AUDIOSPECTROGRAPHIC ANALYSIS OF THE STRIDULATORY SIGNALS OF SOME NORTH AMERICAN CORIXIDAE FOUND SYMPATRIC WITH CENOCORIXA  231  V LIST OF TABLES Table  Page I. T h i c k n e s s o f t h e pegs o f t h e p a r s s t r i d e n s and comparison of the number o f peg rows on the p a r s s t r i d e n s and the number o f impacts per p u l s e  27  I I . N u m e r i c a l c h a r a c t e r i s t i c s of C e n o c o r i x a s i g n a l s . . . 3 1 I I I . A c t i v i t i e s o f _C. b i f i d a males under v a r i o u s test conditions IV. A c t i v i t i e s o f C_. b i f i d a females under v a r i o u s test conditions V. D i s t a n c e f o r r e c o g n i t i o n o f s i g n a l s o f o p p o s i t e sex i n some C e n o c o r i x a s p e c i e s i n sand l i n e d bathtub  110 112  119  VI.  S p e c i f i c d i f f e r e n c e s observed i n mating beh a v i o r o f C e n o c o r i x a males  120  VII.  S p e c i f i c d i f f e r e n c e s observed i n mating beh a v i o r o f C e n o c o r i x a females  121  V I I I . Response o f C e n o c o r i x a males t o p l a y b a c k o f male s i g n a l s  130  IX.  Response o f C e n o c o r i x a males t o p l a y b a c k o f female s i g n a l s  X. Response o f C e n o c o r i x a females t o p l a y b a c k of male s i g n a l s XI.  131 132  Response of C e n o c o r i x a females t o p l a y b a c k of female s i g n a l s  133  X I I . Response o f C e n o c o r i x a spp. t o p l a y b a c k o f s i g n a l s of s y m p a t r i c s p e c i e s o f o t h e r Corixidae '  134  X I I I . E s t i m a t e s o f the magnitude o f d i f f e r e n t l a t i n g mechanisms i n C e n o c o r i x a  iso-  187  vi LIST OF FIGURES Figure  Page  1 . T e r m i n o l o g y used i n t h e d e s c r i p t i o n s stridulatory signals  of the  15  2. S t e r e o s c a n photograph of the f r o n t l e g o f (J. b l a i s d e l l i male showing t h e l o c a t i o n o f the p a r s s t r i d e n s  24  3 . S t e r e o s c a n photograph o f t h e head o f CJ. b l a i s d e l l i female showing the l o c a t i o n of the p l e c t r u m  25  4. S t e r e o s c a n photographs o f the s t r i d u l a t o r y apparatus o f _C. b l a i s d e l l i  28  5 . Sound spectrograms of C_. b i f i d a s i g n a l s 6. Sound spectrograms o f C_. k u i t e r t i  ,  signals  38 38  7. Sound spectrograms o f CJ. a n d e r s o n i s i g n a l s  39  8. Sound spectrograms o f CJ. u t a h e n s i s s i g n a l s  39  9. Sound spectrograms of _C. d a k o t e n s i s s i g n a l s  40  10. Sound spectrograms o f C_. b l a i s d e l l i s i g n a l s  40  1 1 . Sound s p e c t r o g r a m o f C_. b l a i s d e l l i mounting signal 12.  4 l  Sound spectrograms o f CJ. w i l e y a e s i g n a l s  1 3 . Sound spectrograms o f CJ. e x p l e t a  signals  42 42  14. E f f e c t o f temperature on s i g n a l d u r a t i o n i n C_. b i f i d a , C. k u i t e r t i , and CJ. a n d e r s o n i 45 1 5 . E f f e c t o f temperature on s i g n a l d u r a t i o n i n C_. u t a h e n s i s , C_. d a k o t e n s i s , and C_. b l a i s d e l l i . ... 46 1 6 . E f f e c t o f temperature on s i g n a l d u r a t i o n i n (J. w i l e y a e and CJ. e x p l e t a 47 17.  E f f e c t of temperature on p u l s e r a t e i n CJ. b i f i d a signals  48  1 8 . E f f e c t of temperature on p u l s e r a t e i n CJ. k u i t e r t i male s i g n a l s . . . .  49  1 9 . E f f e c t o f temperature on p u l s e r a t e i n (J_. a n d e r s o n i male s i g n a l s  50  vii Figure  Page  20.  E f f e c t o f temperature on p u l s e r a t e i n C_. a n d e r s o n i and C_. u t a h e n s i s female s i g n a l s  51  21.  E f f e c t o f temperature on p u l s e r a t e i n C_. u t a h e n s i s male s i g n a l s  52  2 2 . E f f e c t o f temperature on p u l s e r a t e i n C_. dakotensis signals  53  2 3 . E f f e c t o f temperature on p u l s e r a t e i n C_. b l a i s d e l l i signals  54  2k.  E f f e c t o f temperature on p u l s e r a t e i n _C. w i l e y a e male s i g n a l s  55  E f f e c t o f temperature on p u l s e r a t e i n C_. w i l e y a e female s i g n a l s  56  2 6 . E f f e c t o f temperature on p u l s e r a t e i n C_. expleta signals  57  25.  27.  E f f e c t o f temperature on r e p e t i t i o n r a t e o f " u n i p u l s a t e p u l s e groups" o f t h e second p a r t of t h e s i g n a l i n _C. b l a i s d e l l i male  58  2 8 . E f f e c t o f temperature on r e p e t i t i o n r a t e o f p u l s e groups o f t h e second p a r t o f t h e s i g n a l i n C_. w i l e y a e male  59  2 9 . E f f e c t o f temperature on r e p e t i t i o n r a t e o f p u l s e groups o f t h e s i g n a l s i n _C. e x p l e t a  60  30.  Sound spectrograms o f sounds produced as a byproduct o f c l e a n i n g movements  31.  Sequence o f g e n e r a t i o n s o f C.. b i f i d a i n E a s t Lake a c c o r d i n g t o s t a n d a r d sweep samples i n 1 9 6 9 . . 6 6  32.  Sequence o f g e n e r a t i o n s o f £. b i f i d a i n Long Lake a c c o r d i n g t o s t a n d a r d sweep samples i n I 9 6 9 . . 6 7  33.  Sequence o f g e n e r a t i o n s o f C_. e x p l e t a i n LB2 a c c o r d i n g t o s t a n d a r d sweep samples i n 1969  34.  D a i l y maximum and minimum temperatures a t Westw i c k Lake and B o i t a n o Lake d u r i n g t h e summer o f  ' 1969  35.  D a i l y maximum and minimum temperatures i n f i v e l a k e s i n t h e i n t e r i o r B r i t i s h Columbia d u r i n g the summer o f 1969  62  68  69  70  viii Figure 36.  37.  Page S p e c i f i c c o n d u c t i v i t y o f s u r f a c e water i n e i g h t water bodies i n t h e i n t e r i o r B r i t i s h Columbia d u r i n g t h e summer o f 1969  71  Sequence o f g e n e r a t i o n s o f £. a n d e r s o n i i n C u s t e r g o l f c o u r s e pond a c c o r d i n g t o s t a n d a r d sweep samples i n 1970  74  3 8 . D a i l y maximum and minimum t e m p e r a t u r e s a t S u r r e y M u n i c i p a l H a l l Weather S t a t i o n , B r i t i s h Columbia, d u r i n g t h e p e r i o d o f November 1969 - October 197O 39-  75  L i g h t m i c r o s c o p e photographs o f s t a g e s o f o v a r i a n development i n C_. b i f i d a  77  40. L i g h t m i c r o s c o p e photographs o f s t a g e s o f spermatogenesis i n C_. b i f i d a  78  41. Presence o f s e x u a l l y mature specimens o f C_. b i f i d a i n E a s t Lake and Long Lake i n 1969  8l  42. Presence o f s e x u a l l y mature specimens o f C_. e x p l e t a i n LB2 i n 1969  82  4 3 . Presence o f s e x u a l l y mature specimens o f _C. a n d e r s o n i i n C u s t e r g o l f c o u r s e pond d u r i n g the summer o f 1970  84  44. 45.  L i g h t m i c r o s c o p e photograph o f a f o l l i c l e an a r r e s t e d t e s t i s o f _C. b i f i d a  from  L i g h t m i c r o s c o p e photograph o f a f o l l i c l e a mature t e s t i s o f _C. b i f i d a  from  87 88  46. Observed a n n u a l rhythm o f s t r i d u l a t i o n and sexual maturity i n four species of Cenocorixa 47.  92  I n s i t u o b s e r v a t i o n s on d i e l p e r i o d i c i t y o f t h e s t r i d u l a t i n g a c t i v i t y o f C_. b i f i d a and _C. exple ; eta ;  :  99  48. L a b o r a t o r y experiments on d i e l p e r i o d i c i t y o f the s t r i d u l a t i n g a c t i v i t y o f _C. b i f i d a , _C. k u i t e r t i , and C_. w i l e y a e  100  49. L a b o r a t o r y experiment on d i e l p e r i o d i c i t y o f the s t r i d u l a t i n g a c t i v i t y o f _C. a n d e r s o n i  101  5 0 . L a b o r a t o r y experiments on d i e l p e r i o d i c i t y o f the s t r i d u l a t i n g a c t i v i t y o f C.. d a k o t e n s i s and C. e x p l e t a  102  ix re 51.  Page L a b o r a t o r y experiment on d i e l p e r i o d i c i t y o f the s t r i d u l a t i n g a c t i v i t y o f (J_. b l a i s d e l l i  103  5 2 . R e p e t i t i o n r a t e o f s i g n a l s produced by 1 0 male specimens i n a sample f o u r minute t e s t p e r i o d . . . . 1 0 5 5 3 . Diagram on t h e sequence o f events i n a s u c c e s s f u l mating i n _C. b i f i d a  117  5 4 . Known g e o g r a p h i c d i s t r i b u t i o n o f (J. b i f i d a and C. k u i t e r t i  140  5 5 . Known g e o g r a p h i c d i s t r i b u t i o n o f CJ. a n d e r s o n i and (J_. u t a h e n s i s l 4 l 5 6 . Known g e o g r a p h i c d i s t r i b u t i o n o f (J_. d a k o t e n s i s and C_. b l a i s d e l l i  142  5 7 . Known g e o g r a p h i c d i s t r i b u t i o n o f C_. w i l e y a e and (J. e x p l e t a  143  5 8 . Example o f a r t i f a c t s c r e a t e d by improper a n a l y s i s of a Cenocorixa s i g n a l  151  59-  Summary o f t h e r e g r e s s i o n l i n e s o f temperature e f f e c t on p u l s e r a t e i n C e n o c o r i x a male s i g n a l s . . 1 5 4  60.  Summary o f temperature e f f e c t on s i g n a l i n C e n o c o r i x a males  duration 156  6 1 . Summary o f t h e d i e l p e r i o d i c i t y o f t h e s t r i d u l a t i n g a c t i v i t y of C e n o c o r i x a males  184  6 2 . Diagram o f suggested i n c r e a s i n g c o m p l e x i t y o f s i g n a l s o f C e n o c o r i x a males  189  6 3 . Suggested e v o l u t i o n ' o f C e n o c o r i x a s p e c i e s  191  APPENDIX I : 64.  D o r s a l view o f p o s t e r i o r abdominal t e r g a o f male i n CJ. b i f i d a and (J_. k u i t e r t i 219 65.. D o r s a l view o f p o s t e r i o r abdominal t e r g a o f male i n (J_. a n d e r s o n i and (J. u t a h e n s i s 220 6 6 . D o r s a l v i e w o f p o s t e r i o r abdominal t e r g a o f male i n CJ. d a k o t e n s i s and CJ. b l a i s d e l l i 221 6 7 . D o r s a l v i e w o f p o s t e r i o r abdominal t e r g a o f male i n C. w i l e y a e and C_. e x p l e t a 222  X  Figure  Page  6 8 . I n t r a s p e c i f i c v a r i a t i o n i n arrangement of p a l a r pegs i n C_. b i f i d a 6 9 . Arrangement o f p a l a r pegs I n C_. k u i t e r t i , C_. a n d e r s o n i , C_. u t a h e n s i s , and S_. d a k o t e n s i s  223 224  7 0 . Arrangement of p a l a r pegs i n C_. b l a i s d e l l i , C_. w i l e y a e , and C_. e x p l e t a  225  7 1 . T y p i c a l shapes o f the r i g h t parameres i n Cenocorixa species  226  7 2 . I n t r a s p e c i f i c v a r i a t i o n i n shape o f r i g h t paramere i n C_. b i f i d a  227  73-  I n t r a s p e c i f i c v a r i a t i o n i n shape o f f i g h t paramere o f _C. k u i t e r t i and C_. a n d e r s o n i  228  7 4 . I n t r a s p e c i f i c v a r i a t i o n i n shape o f r i g h t paramere i n C_. u t a h e n s i s , C_. d a k o t e n s i s , and C_. b l a i s d e l l i  229  75-  I n t r a s p e c i f i c v a r i a t i o n i n shape o f r i g h t paramere i n _C. w i l e y a e and C_. e x p l e t a  230  APPENDIX I I : 7 6 . Sound spectrograms o f the male c a l l s o f C o r i s e l l a t a r s a l i s and C a l l i c o r i x a v u l n e r a t a  235  7 7 - Sound spectrograms o f the male c a l l s o f C a l l i c o r i x a a u d e n i and C_. t e t o n i  235  7 8 . Sound spectrograms of the s i g n a l s o f S i g a r a omani and S. n e v a d e n s i s  236  xi ACKNOWLEDGEMENTS The a u t h o r wishes t o express h i s most s i n c e r e g r a t i t u d e to Dr. G. G. E. Scudder f o r h i s encouragement, g u i d a n c e , and c r i t i c a l s u p e r v i s i o n d u r i n g t h e e n t i r e phase o f t h i s work. Thanks a r e a l s o due t o Dr. N. R. L i l e y f o r c r i t i c a l  dis-  c u s s i o n s on b e h a v i o r a l problems. A l s o Drs. A. B. A c t o n and J. D. M c P h a i l r e a d t h e m a n u s c r i p t . Mr. L. Veto's  assistance  i n u s i n g t h e Scanning e l e c t r o n m i c r o s c o p e , and Mrs. D. L a u r i e n t e ' s programming and computing  of the pulse rate  d a t a , a r e a p p r e c i a t e d . S p e c i a l thanks a r e due t o my w i f e who  a l l o w e d me t o spend  " a l l " my time i n p r e p a r i n g t h i s  thesis. F i n a n c i a l support f o r t h e s t u d y was o b t a i n e d from t h e f o l l o w i n g : N a t i o n a l Research C o u n c i l o f Canada ( t h r o u g h Dr. G. G. E. S c u d d e r ) , The U n i v e r s i t y o f B r i t i s h  Columbia,  The U n i v e r s i t y o f H e l s i n k i , F i n l a n d , and Werner H a c k l i n Foundation, P o r i ,  Finland.  i)  1 I . INTRODUCTION  D u r i n g t h e p a s t hundred y e a r s a c o n s i d e r a b l e  literature  has accumulated on i n s e c t sounds. The e a r l y s t u d i e s on these sounds, however, were o n l y notes on t h e d i f f e r e n t sounds produced by v a r i o u s s p e c i e s , and s u g g e s t i o n s  on t h e mode o f  p r o d u c t i o n o f these sounds. I t i s o n l y d u r i n g t h e l a s t 30 years t h a t t e c h n i c a l apparatus  has been developed  and  thorough i n v e s t i g a t i o n s on b i o a c o u s t i c s u n d e r t a k e n by p h y s i o l o g i s t s and e t h o l o g i s t s . These s t u d i e s have r e s u l t e d i n a) thorough d e s c r i p t i o n o f t h e mechanism o f sound p r o d u c t i o n , b) d e t a i l e d a n a l y s i s of t h e s i g n a l s , and c) p l a y b a c k iments u s i n g p r e v i o u s l y r e c o r d e d  or a r t i f i c i a l  I n i n s e c t s , a c c o r d i n g t o Dumortier (1963  exper-  signals. a) t h r e e  diff-  e r e n t mechanisms o f sound p r o d u c t i o n c a n be d i s t i n g u i s h e d : 1)  Sound p r o d u c t i o n as a byproduct o f some o t h e r normal  a c t i v i t y , e.g. f l i g h t sound; 2) Sound p r o d u c t i o n by p e r c u s s i o n on t h e substratum,  e.g. t h e k n o c k i n g  o f t h e Death  Watch B e e t l e s ( A n o b i i d a e ) ; 3) Sound p r o d u c t i o n by a s p e c i a l sound p r o d u c i n g The  apparatus.  apparatus  f o r sound p r o d u c t i o n i s o f t e n a v e r y  s p e c i a l i z e d organ, and Dumortier (1963  a  ) separates the  f o l l o w i n g t h r e e c l a s s e s : a) Sound p r o d u c t i o n by passage o f f l u i d (gas o r l i q u i d ) a c r o s s an o r i f i c e , e.g. Death's Head Moth ( A c h e r o n t i a a t r o p o s L.) out through  i s s a i d t o blow a i r i n and  i t s pharynx, p r o d u c i n g w h i s t l i n g sounds; b)  Sound p r o d u c t i o n by v i b r a t i o n o f a membrane ( o t h e r  than  w i n g s ) , e.g. r e p r e s e n t a t i v e s o f Homoptera have a membrane  2 where a s p e c i a l muscle i s a t t a c h e d and c o n t r a c t i o n s o f t h i s muscle cause t h e membrane t o v i b r a t e ; c) Sound p r o d u c t i o n by f r i c t i o n , e.g. c r i c k e t s ( O r t h o p t e r a , G r y l l o d e a ) make sounds by r u b b i n g c e r t a i n p a r t s o f t h e i r wings a g a i n s t each o t h e r . Sound p r o d u c t i o n by f r i c t i o n i s t h e most mechanism used i n i n s e c t s . I t i s o f t e n c a l l e d  widespread  stridulation  and t h i s usage i s adopted h e r e i n ; e t y m o l o g i c a l l y , however, t h i s term c a n be a p p l i e d t o any sound p r o d u c t i o n . The  s t r i d u l a t o r y apparatus  i s composed o f two p a r t s :  a "pars s t r i d e n s " ( a . f i l e , a s t r i g i l ) , -  a special  stridulatory  s u r f a c e w i t h pegs, t e e t h , o r s p i n e s , and a " p l e c t r u m " , a sharp edge, a t o o t h , o r a l i n e o f d e n t i c u l a t i o n s . The sound i s produced by t h e r u b b i n g o f t h e p l e c t r u m on t h e pars s t r i d e n s or v i c e versa. I n f a c t , the d i s t i n c t i o n of the parts i s rather a r t i f i c i a l  and o f t e n i t i s i m p o s s i b l e t o  say which i s which. S e v e r a l attempts have been made t o c l a s s i f y t h e b i o l o g i c a l f u n c t i o n of s t r i d u l a t o r y signals i n i n s e c t s (e.g. B u s n e l , 1963;  1967).  Dumortier,  1963  c; H a s k e l l , 1964;  Alexander,  A l l o f these c l a s s i f i c a t i o n s a r e based p r i m a r i l y on  s t u d i e s on O r t h o p t e r a , and some O r t h o p t e r a n s p e c i e s have s e v e r a l d i f f e r e n t c a l l s apparently having d i f f e r e n t f u n c t i o n s . However, i n most o t h e r i n s e c t s o n l y one o r two s i g n a l s a r e known, and t h e f u n c t i o n o f these s i g n a l s may be d i f f i c u l t t o c l a s s i f y according t o the e x i s t i n g  classifications.  F u n c t i o n a l l y , s i g n a l s which a r e c l a s s i f i e d as c a l l i n g , r i v a l ' s , o r premating in  songs, may a l s o have an i m p o r t a n t  role  s e x u a l i s o l a t i o n o f c l o s e l y r e l a t e d s p e c i e s . T h i s has been  3  shown i n s e v e r a l cases of v e r t e b r a t e s (e.g. D i l g e r , 1956; M a r l e r , 1957; L i t t l e John and Michaud, 1959; Delco,  i960).  G e n e r a l l y these cases f a l l i n t o the c a t e g o r y of p r e m a t i n g i s o l a t i n g mechanisms s i n c e the males produce s p e c i e s s i g n a l s w h i c h a t t r a c t c o n s p e c i f i c females.  specific  Females of o t h e r  s p e c i e s do not respond, and thus p a i r f o r m a t i o n i s f a c i l i t a t e d by the s i g n a l s . I n i n s e c t s such s t u d i e s have been c a r r i e d out m o s t l y  on O r t h o p t e r a  (e.g. Walker, 1957;  Per-  deck, 1958; H a s k e l l , I 9 6 I ; Spooner, 1 9 6 8 ) . I n the water'bug f a m i l y C o r i x i d a e i t has  been known f o r  more t h a n 120 years t h a t some s p e c i e s are a b l e t o s t r i d u l a t e while completely was  submerged. The  f i r s t note on t h i s phenomenon  p u b l i s h e d by B a l l ( 1 8 4 6 ) , who  made o b s e r v a t i o n s  on  the  sounds .of C o r i x a s t r i a t a (L.) [= S i g a r a s t r i a t a ( L . ) ] I n England. A f t e r t h i s , o t h e r notes on s t r i d u l a t i o n of European C o r i x i d a e were p u b l i s h e d  (e.g. Thomson, 1894;  Carpenter,  1894; K i r k a l d y , 1 9 0 1 ) , d e s c r i b i n g the q u a l i t y of the sound (as i t i s h e a r d by the human e a r ) , and i t s apparent mode of p r o d u c t i o n . A l l these notes concerned the s u b f a m i l y C o r i x i n a e * , and the mechanism was  described i n c o r r e c t l y . M i t i s  came c l o s e s t t o the t r u t h by s t a t i n g t h a t the sound  (1936) was  produced by r u b b i n g c e r t a i n s t r i d u l a t o r y areas of the f r o n t femora a g a i n s t the sharp edges of the head about midway between the antennae and l a b i u m ;  the former p a r t being  called  p l e c t r u m and the l a t t e r pars s t r i d e n s . However, u s u a l l y the * The f a m i l y C o r i x i d a e i s t a x o n o m i c a l l y d i v i d e d i n t o s i x subfamilies: Diaprepocorinae, Micronectinae, Stenocorixinae, C y m a t i i n a e , H e t e r o c o r i x i n a e , and C o r i x i n a e . For more d e t a i l s see H u n g e r f o r d ( 1 9 4 8 ) .  4 p l e c t r u m i s a sharp edge, and the pars  s t r i d e n s i s the p a r t  c o n t a i n i n g the s t r i d u l a t o r y pegs, and thus M i t i s ' terminology  w i l l be r e v e r s e d i n the p r e s e n t  (1936)  study.  [For a  more d e t a i l e d r e v i e w of the e a r l y works d e s c r i b i n g the method of sound p r o d u c t i o n i n C o r i x i d a e , see F i n k e  (1968)]  M i t i s ( 1 9 3 6 ) compared the sexes of c e r t a i n C o r i x i n a e and found t h a t o n l y the male had  s t r i d u l a t o r y areas l o c a t e d  on the i n s i d e of the f r o n t femur t h a t c o n t a i n e d  s e v e r a l rows  of s h o r t pegs; these pegs were s a i d t o be absent from the female. F u r t h e r , M i t i s ( 1 9 3 6 ) observed o n l y males t o u l a t e , and t h i s has been concluded  a l s o i n other  strid-  studies  (e.g. S c h a l l e r , 1 9 5 1 ; L e s t o n and P r i n g l e , 1 9 6 3 ) . I n o n l y s p e c i e s have p o s s i b l e female c a l l s been r e p o r t e d : ( i n H a s k e l l , 1 9 5 7 ) and Southwood and L e s t o n t h a t both sexes of A r c t o c o r i s a g e r m a r i  two  Leston  (1959) claim  (Fie'b.) s t r i d u l a t e  d u r i n g the mating p e r i o d , but n o t h i n g more i s s a i d about the s t r i d u l a t i o n of t h i s s p e c i e s . F i n k e ( 1 9 6 8 ) observed some u n u s u a l f a i n t s i g n a l s i n c u l t u r e s of S i g a r a s t r i a t a ( L . ) , but was  unable t o o b t a i n s a t i s f a c t o r y r e c o r d i n g s . However,  she observed t h a t both males and females produced sounds and the mode of p r o d u c t i o n was  these  by r u b b i n g the h i n d  l e g s a g a i n s t the f o r e wings l y i n g above the abdomen. A l s o Moore ( 1 9 6 1 ) observed and r e c o r d e d way  by males of two  Hesperocorixa  sounds' produced i n a s i m i l a r  s p e c i e s of N o r t h A m e r i c a n C o r i x i d a e ,  atopodonta (Hung.) and S i g a r a g r o s s o l i n e a t a  Hung.; no movements of the f r o n t l e g s were observed d u r i n g these  stridulations. M i t i s ( 1 9 3 6 ) compared the morphology of the  strid-  5 u l a t o r y areas on t h e f r o n t femora o f males o f s e v e r a l s p e c i e s . He found t h a t t h e t h i c k n e s s o f t h e pegs c o r r e l a t e w i t h t h e l o u d n e s s o f t h e sounds produced (as judged by t h e human e a r ) : the t h i c k e r t h e pegs t h e l o u d e r t h e s i g n a l . F u r t h e r , he found t h a t t h e s u b f a m i l y  C o r i x i n a e c o n t a i n s both s t r i d u l a t i n g  and n o n s t r i d u l a t i n g s p e c i e s , and a c c o r d i n g  t o the s t r u c t u r e  of t h e pegs on f r o n t femora he was a b l e t o p r e d i c t i f a s p e c i e s was a b l e t o s t r i d u l a t e . A s i m i l a r comparison o f t h e s t r i d u l a t o r y areas was made by Hungerford ( 1 9 ^ 8 ) , who gave a l i s t o f 7 5 w e s t e r n hemisphere s p e c i e s o f C o r i x i n a e supposed to s t r i d u l a t e although  observations  of a c t u a l s t r i d u l a t i o n  e x i s t f o r o n l y one o f them. In contrast to the subfamily of t h e genus M i c r o n e c t a  Corixinae, several  (subfamily Micronectinae)  observed t o s t r i d u l a t e a l t h o u g h  species  have been  t h e y do n o t have s t r i d -  u l a t o r y pegs on t h e f r o n t femora. M i t i s ( 1 9 3 6 ) and Southwood and L e s t o n by a s t r i g i l ,  ( 1 9 5 9 ) suggest t h a t t h e y produce t h e sound  an organ l o c a t e d d o r s a l l y on t h e s i x t h abdominal  segment: t h i s organ would be rubbed a g a i n s t t h e tergum o f t h e f i f t h segment o r a g a i n s t some p a r t s o f g e n i t a l i a . Males o f most s p e c i e s o f t h e s u b f a m i l y  C o r i x i n a e a l s o have t h e s t r i g i l ,  but i t s f u n c t i o n seems t o be f o r a t t a c h i n g t o t h e female during c o p u l a t i o n (Larsen,  1938).  C o r i x i n a e and M i c r o n e c t i n a e  are the only  subfamilies  o f C o r i x i d a e i n which s t r i d u l a t i n g s p e c i e s have been r e p o r t e d so f a r . R e p r e s e n t a t i v e s  o f C y m a t i i n a e (genus Cymatia) a r e  known t o be unable t o s t r i d u l a t e ( M i t i s , 1 9 3 6 ) , and o b s e r v a t i o n s on o t h e r s u b f a m i l i e s a r e l a c k i n g .  6  Only t h r e e p u b l i c a t i o n s e x i s t on a u d i o s p e c t r o g r a p h i c a n a l y s i s o f s i g n a l s o f C o r i x i n a e . Moore  (1961)  g i v e s sound  spectrograms o f s i g n a l s produced by H e s p e r o c o r i x a  a t o p o d o n t a,  and from h i s f i g u r e i t i s p o s s i b l e t o see t h a t t h e s t r i d u l a t i o n o f t h i s s p e c i e s i s composed o f more o r l e s s i r r e g u l a r p u l s e s , t h e main f r e q u e n c y  a r e a o f t h e sound being  k i l o c y c l e s p e r second. H a s k e l l  (1961)  gives  7-8  oscillograms  of two c a l l s produced by S i g a r a d o r s a l i s ( L e a c h . ) .  These  f i g u r e s do n o t g i v e any i n f o r m a t i o n on t h e f r e q u e n c y o f the sound, but i t c a n be seen t h a t one o f t h e s i g n a l s i s composed o f r e g u l a r l y r e p e a t e d  p u l s e s , w h i l e t h e o t h e r one  i s composed o f p u l s e groups r e p e a t e d Finke  (1968)  with regular i n t e r v a l s .  g i v e s both spectrograms and o s c i l l o g r a m s o f  the c a l l s o f two s p e c i e s , S i g a r a s t r i a t a (L.) and C a l l i c o r i x a praeusta  (Fie'b.). I n these f i g u r e s t h e c a l l s o f  S_. s t r i a t a appear t o be v e r y much l i k e t h e c a l l s o f S_. dorsalis i nHaskell call,  (1961),  w h i l e C_. p r a e u s t a o n l y has one  t h i s being composed o f two p a r t s , each w i t h r e g u l a r l y  repeated  p u l s e s , b u t w i t h d i f f e r e n t p u l s e r a t e . The main  frequency  a r e a f o r both s p e c i e s i n F i n k e ' s  (1968)  study  appear t o be 3-6 k c / s e c , w i t h some h i g h e r overtones 16 kc/sec  up t o  and over.  Hagemann (19IO) d e s c r i b e d t h e tympanal organ o f C o r i x i d a e l o c a t e d near t h e wing base on t h e mesothorax. Schaller  (1951)  demonstrated i n v a r i o u s experiments t h a t  a c o u s t i c s t i m u l i a r e r e c e i v e d by t h i s organ, a l t h o u g h i t a l s o might have a f u n c t i o n as a h y d r o s t a t i c p r e s s u r e indicator.  7  The f u n c t i o n o f s t r i d u l a t i o n i n C o r i x i n a e has  been  d i s c u s s e d a number o f t i m e s . Because i t i s commonly t h a t these i n s e c t s s t r i d u l a t e d u r i n g the b r e e d i n g  observed  season 1968)  ( M i t i s , 1 9 3 6 ; S c h a l l e r , 1 9 5 1 ; F i n k e , 1 9 6 8 ; Jansson,  and have s p e c i e s s p e c i f i c s i g n a l s , i t . i s supposed t h a t the song i s combined w i t h s e x u a l b e h a v i o r . S c h a l l e r  (1951)  r e p o r t s t h a t the song of male S_. s t r i a t a i s a c o u r t s h i p song c a u s i n g females  t o swim r a p i d l y i n s m a l l c i r c l e s ,  which i s an e f f e c t i v e mechanism because the males  attempt  t o c o p u l a t e w i t h any moving o b j e c t o f s u i t a b l e s i z e . A l s o Finke  (1968)  observed  o f the females Larsen  (1938)  an i n c r e a s e i n the swimming a c t i v i t y  i n the presence and Jansson  o f the male signals.. However,  (1968)  d i d not observe  e f f e c t o f the song of the males upon f e m a l e s . Larsen  (1938)  any  visible  In a d d i t i o n ,  observed males o f C o r i x a d e n t i p e s (Thorns.)  s t r i d u l a t e both i n e a r l y s p r i n g and i n l a t e f a l l ,  and  to  noted  t h a t the l a t e f a l l s t r i d u l a t i o n i s not i n c o n n e c t i o n w i t h b r e e d i n g . To d a t e , no comprehensive study has been undert a k e n on the f u n c t i o n of s t r i d u l a t i o n i n t h i s group o f water bugs. The aim of the t h e s i s i s t o o b t a i n a more d e t a i l e d understanding  o f s t r i d u l a t i o n i n the C o r i x i n a e . The genus  C e n o c o r i x a Hungerford  was  chosen f o r study because i t c o n t a i n s  s e v e r a l c l o s e l y r e l a t e d s p e c i e s which are o f t e n d i f f i c u l t to i d e n t i f y a c c o r d i n g t o m o r p h o l o g i c a l c h a r a c t e r s ( c f . Appendix I ) and which c o u l d be p r e d i c t e d t o s t r i d u l a t e because t h e y have s t r i d u l a t o r y pegs on the f r o n t femora. A l l s p e c i e s i n the genus a l s o have t h e i r geographic  d i s t r i b u t i o n i n western  8 N o r t h A m e r i c a ( H u n g e r f o r d , 1 9 ^ 8 ) , and both a l l o p a t r i c and s y m p a t r i c s i t u a t i o n s can be s t u d i e d . Two s p e c i e s i n p a r t i c u l a r , C_. b i f i d a (Hung. ) and C_. e x p l e t a ( U h l e r ) a r e abundant i n B r i t i s h Columbia, where t h e y occur  allopatric-  a l l y and s y m p a t r i c a l l y (Scudder, 1 9 6 9 a; 1 9 6 9 b ) , and so t h e y were s t u d i e d most i n t e n s i v e l y .  9 I I . MATERIAL AND METHODS  1.  Sampling and h a n d l i n g o f specimens The g e n e r a l d i s t r i b u t i o n o f the s p e c i e s was determined  from p u b l i s h e d r e c o r d s ( H u n g e r f o r d , 1948;  Lansbury, I 9 6 0 ;  Scudder, 1969 a ) , t h e n s p e c i f i c l o c a l i t i e s t o be s t u d i e d were s e l e c t e d f o r a l l the s p e c i e s . Bugs were c o l l e c t e d u s i n g a sweep net., and were t r a n s p o r t e d t o t h e l a b o r a t o r y i n one g a l l o n thermos jugs about h a l f f i l l e d w i t h l a k e water. I n cases when t h e t r a n s p o r t a t i o n t o o k s e v e r a l days ( f r o m C a l i f o r n i a and Utah) t h e thermos Jugs were c a r r i e d i n s t y r o f o a m i c e c h e s t s c o n t a i n i n g m e l t i n g i c e ; i n t h i s way t h e bugs were kept a t about 8-10°C during transportation. In  t h e l a b o r a t o r y t h e bugs were t r a n s f e r r e d t o 30x24x10  cm t r a n s p a r e n t c o v e r e d p l a s t i c t r a y s ( h e n c e f o r t h c a l l e d c u l t u r e t r a y s ) w i t h about 4-5 l i t r e s o f n a t u r a l l a k e water, so t h a t t h e depth o f t h e water was about 5 cm. P i e c e s o f p l a s t i c s c r e e n were p l a c e d on t h e bottom o f the c u l t u r e t r a y s t o p r o v i d e s u p p o r t f o r t h e bugs w h i l e r e s t i n g .  Culture  t r a y s were t h e n kept e i t h e r i n a c o n s t a n t temperature c a b i n e t at  5°0 u n t i l needed, o r i n t h e l a b o r a t o r y a t a temperature  of  about 21-24°C (room t e m p e r a t u r e ) f o r v a r i o u s e x p e r i m e n t s .  P h o t o p e r i o d i n both cases was 16 hours a r t i f i c i a l day, except i n experiments r e q u i r i n g n a t u r a l l i g h t  l i g h t per conditions.  A t 5°C t h e bugs s u r v i v e d s e v e r a l months w i t h o u t any a t t e n t i o n . A t room temperature t h e y were f e d d a i l y on f r o z e n b r i n e shrimp [Artemia s a l i n a ( L . ) , L o n g l i f e F i s h Food P r o d u c t s , D i v . o f  10 S t e r n o I n d u s t r i e s I n c . , H a r r i s o n , N . J . ] . Three o f the s p e c i e s s t u d i e d , C_. b i f i d a , C_. a n d e r s o n i , and ^C. e x p l e t a produced t h r e e c o n s e c u t i v e g e n e r a t i o n s i n the l a b o r a t o r y on t h i s d i e t , and a l l the o t h e r s p e c i e s s u r v i v e d w i t h o u t t r o u b l e . Thus t h i s food s u p p l y was  considered  sufficient  a l t h o u g h the r e a r e d specimens always were s l i g h t l y s m a l l e r t h a n the f i e l d caught i n s e c t s ( c f . Jansson,  1969).  Owing t o the r a p i d r o t t i n g of excess food i n the c u l t u r e s , c o n t i n u o u s v e n t i l a t i o n was accomplished  r e q u i r e d . This  was  by use of a i r stones run o f f the a i r s u p p l y  t o the l a b o r a t o r y .  2. L i f e c y c l e I n o r d e r t o i n v e s t i g a t e how  the annual rhythm o f  strid-  u l a t i o n c o r r e l a t e s w i t h the l i f e c y c l e , p o p u l a t i o n s o f _C. b i f i d a and C_. e x p l e t a i n s e l e c t e d l a k e s i n the  Southern  I n t e r i o r P l a t e a u of B r i t i s h Columbia were s t u d i e d . Samples were t a k e n a t 1 - 3 weeks i n t e r v a l s between May 1 9 6 9 . The  and  October  l a k e s s t u d i e d were: A) C h i l c o t i n , Beeche's P r a i r i e  a r e a : E a s t Lake (= R a c e t r a c k i n Scudder, 1 9 6 9 a; 1 9 6 9 b ) , Barnes Lake (= Box 4 ) , and Lake Lye C a r i b o o , Springhouse  (= Box 2 0 - 2 1 ) ;  B)  a r e a : Westwick Lake, B o i t a n o Lake,  and B o i t a n o Lake N o r t h End;  C) C a r i b o o , Green Timbers  P l a t e a u between C l i n t o n and Gang Ranch: Long Lake; Kamloops, Lac du B o i s a r e a : LB2.  D)  The c h a r a c t e r i s t i c s o f  the l a k e s a r e g i v e n i n Scudder ( 1 9 6 9 a ) . Sampling i n c l u d e d 1 0 minutes of tape r e c o r d i n g i n s i t u ,  11 a temperature r e c o r d i n g , a 1 0 s t a n d a r d sweep sample ( 1 standard  sweep = about one metre l o n g v i g o r o u s back:  and f o r t h sweep w i t h sweep net a t the depth of 2 0 - 3 0 cm, consecutive  sweeps were t a k e n by moving s l o w l y p a r a l l e l  t o the shore l i n e ) . Some a d d i t i o n a l a d u l t c o r i x i d s were a l s o c o l l e c t e d . Sampling was  done a t the same l o c a l i t y i n  the l a k e s each time. Sweep samples were p r e s e r v e d  i n 70  per cent a l c o h o l , and a d d i t i o n a l a d u l t s were p r e s e r v e d a l c o h o l or m o d i f i e d a l c o h o l i c Bouin's f l u i d  in  (Ewen, 1 9 6 2 ) .  I n a d d i t i o n t o r e c o r d i n g the temperature at the time o f each sample, a i r and water temperatures were c o n t i n u o u s l y recorded  a t Westwick Lake u s i n g a B r i s t o l p o r t a b l e two  r e c o r d i n g thermometer model 2T 501—1A-1B ( B r i s t o l  pen  Co.,  Waterbury, Conn.). Continuous r e c o r d s of the temperature i n s h a l l o w water i n a l l water bodies were a l s o o b t a i n e d u s i n g Ryan model D-15 Co.,  waterproof  recorders  (Ryan Instrument  S e a t t l e , Wash.). C o n d u c t i v i t y of water samples  r e c o r d e d monthly w i t h a Radiometer type CDM meter (Radiometer Co.,  by  was  2 d conductivity  Copenhagen, Denmark).  From, the s t a n d a r d sweep samples the i d e n t i t y and number of a d u l t s and l a r v a e i n the d i f f e r e n t i n s t a r s were counted and thus the sequence of g e n e r a t i o n s  f o r the s p e c i e s  was  determined. The a d u l t specimens of v a r i o u s s p e c i e s o c c u r r i n g i n the l a k e s were i d e n t i f i e d a c c o r d i n g to Hungerford The  (1948).  l a r v a e o f C_. b i f i d a and C_. e x p l e t a were i d e n t i f i e d  a c c o r d i n g t o Scudder ( 1 9 6 6 ) , and the l a r v a e of o t h e r c o u l d be s e p a r a t e d  from C e n o c o r i x a  species  l a r v a e a c c o r d i n g t o some  c h a r a c t e r s common t o both a d u l t s and l a r v a e ( c f . Jansson,  1969),  12 and  a key o f J a n s s o n and Scudder ( i n p r e p a r a t i o n ) .  In iden-  t i f i c a t i o n o f a d u l t specimens from samples t a k e n a t a time when two g e n e r a t i o n s  o v e r l a p , t h e r e l a t i v e age o f t h e  specimens was determined a c c o r d i n g  t o t h e i r s o f t n e s s and  c o l o r : o l d specimens a r e h a r d and d a r k l y pigmented w h i l e young ones a r e s o f t and l i g h t l y pigmented. From p r e s e r v e d a d u l t m a t e r i a l t h e development o f gonads was s t u d i e d i n t h e l a b o r a t o r y ; females were examined by opening t h e abdomen d o r s a l l y and o b s e r v i n g absence o f c h o r i o n a t e d  t h e presence o r  eggs; a l c o h o l p r e s e r v e d males were  s t u d i e d by p l a c i n g them i n t o d i s t i l l e d water f o r 6 - l 8 hours and  t h e n removing t h e t e s t e s . Testes were t h e n s t a i n e d by  a method u s i n g both a s o l u t i o n o f n a t u r a l o r c e i n  (10-15  m i n u t e s ) and s y n t h e t i c o r c e i n  (15-20  erature  and f i n a l l y squashed  (Strickberger,  1962),  m i n u t e s ) a t room templightly  on a m i c r o s c o p e s l i d e w i t h a c o v e r s l i p . I n these p r e p a r a t i o n s t h e c h r o m a t i n s t a i n e d dark p u r p l e and t h e stages o f spermatogenesis c o u l d e a s i l y be i d e n t i f i e d . The r e s u l t s obtained serial  by u s i n g t h i s method were c o n f i r m e d by making  s e c t i o n s o f t e s t e s and s e m i n a l v e s i c l e s u s i n g t h e  m a t e r i a l preserved i n modified  a l c o h o l i c Bouin's f l u i d .  D u r i n g t h e summer o f 1 9 7 0 t h e same sampling methods were a p p l i e d t o p o p u l a t i o n s  o f _C. a n d e r s o n i and C_. b l a i s d e l l i  a t t h e f o l l o w i n g l o c a l i t i e s : A) Washington, Whatcom County, Custer:  a g o l f c o u r s e pond (C_. a n d e r s o n i ) ;  B) B r i t i s h  Columbia, Vancouver: semitemporary pond a t t h e c o r n e r o f 1 6 t h Avenue and Wesbrook C r e s c e n t ;  M a c C l e e r y G o l f Course:  a r t i f i c i a l pond (C^. b l a i s d e l l i ) . However, t h e annual rhythm  of  s t r i d u l a t i o n was t e s t e d i n t h e l a b o r a t o r y r a t h e r t h a n  i n the f i e l d  because the p o p u l a t i o n s were not v e r y dense.  A l s o the t e s t i s squash..preparations were made from f r e s h r a t h e r t h a n a l c o h o l p r e s e r v e d m a t e r i a l . Temperature r e c o r d e r s c o u l d not be used d u r i n g the summer o f 1 9 7 0 *  but d a t a on  a i r t e m p e r a t u r e s a t S u r r e y M u n i c i p a l H a l l weather  station,  B r i t i s h Columbia, were o b t a i n e d f o r comparison w i t h the a i r t e m p e r a t u r e s i n the i n t e r i o r .  3.  Stridulation A l l r e c o r d i n g s were made w i t h a p o r t a b l e / m a i n s tape  r e c o r d e r (Uher 4000 R e p o r t - L ) , t y p e L C - 1 0 hydrophone  (Atl-  a n t i c R e s e a r c h Co., A l e x a n d r i a , V a . ) , Ampex 34l and 64l tapes (Ampex Co., Redwood C i t y , C a l . ) . Tape speed i n the tape r e c o r d e r was always 1 9 cm p e r second except i n the d i e l p e r i o d i c i t y experiments when 2.4  cm p e r second  was used. B a t t e r y o p e r a t i o n was used o n l y under  speed  field  c o n d i t i o n s . Owing t o the f a i n t n e s s o f the s i g n a l s o f some C e n o c o r i x a s p e c i e s , maximum i n p u t was always used w h i l e r e c o r d i n g . The s i g n a l s were a n a l y s e d on a sound  spectro-  g r a p h type 6 7 5 M i s s i l y s e r (Kay E l e c t r i c Co., P i n e Brook, N.J.). S e t t i n g s used i n the s p e c t r o g r a p h w h i l e a n a l y s i n g were as f o l l o w s : i n p u t and reproduce VU - 1 . 5 f o r peaks o f the  s i g n a l s , mark l e v e l 6 . 5 , shape f l a t , bandwidth  for  g e n e r a l f i g u r e s o f the s i g n a l s and wide f o r d e t a i l e d  a n a l y s i s o f the p u l s e s t r u c t u r e .  narrow  1 T e r m i n o l o g y used i n t h e d e s c r i p t i o n s o f t h e s i g n a l s i s as f o l l o w s : ( F i g . 1 ) : Impact: s h o r t e s t d i s t i n g u i s h a b l e element o f a s i g n a l (can o n l y be seen i n t h e d e t a i l e d f i g u r e s o f p u l s e s t r u c t u r e T h i s i s n o t t h e same as a sound wave, b u t would appear t o be a c o m b i n a t i o n  o f s e v e r a l sound waves.  P u l s e : t h e e m i s s i o n r e s u l t i n g from t h e passage o f t h e p a r s s t r i d e n s over t h e p l e c t r u m : a complete c y c l e o f t h e apparatus  b e g i n n i n g and ending a t t h e p o s i t i o n o f r e s t .  T h i s i s t h e common concept o f a p u l s e i n b i o a c o u s t i c s , which d i f f e r s from t h e p h y s i c a l d e f i n i t i o n o f a p u l s e . P u l s e i n t e r v a l : t h e i n t e r v a l between two c o n s e c u t i v e pulses. P u l s e s t r u c t u r e : arrangement o f impacts  i n a pulse.  P u l s e group: a d i s t i n c t group o f p u l s e s w i t h i n a s i g n a l P u l s e group i n t e r v a l : t h e i n t e r v a l between two p u l s e groups. I n some s i g n a l s t h i s i s c l e a r l y l o n g e r t h a n t h e p u l s e i n t e r v a l , but i n some cases i t may be almost e q u a l t o a p u l s e i n t e r v a l . However, i n t h e l a t t e r case t h e r e i s a c l e a r d i f f e r e n c e between t h e p u l s e s o f t h e p u l s e groups and t h i s d e f i n e s t h e l o c a t i o n o f t h e p u l s e group i n t e r v a l . Pulse r a t e : r e p e t i t i o n rate of pulses w i t h i n a stated time  (second). P u l s e group r a t e : r e p e t i t i o n r a t e o f p u l s e groups  w i t h i n a s t a t e d time  (second).  M a i n f r e q u e n c y a r e a : t h e f r e q u e n c y range a t which t h e amplitude  o f the sound i s s t r o n g e s t (appears  a r e a i n t h e sound  spectrograms).  as t h e d a r k e s t  15  1  SECONDS F i g . 1. Terminology used i n the d e s c r i p t i o n s of the s t r i d u l a t o r y s i g n a l s . A b s c i s s a : time ( s e c o n d s ) ; o r d i n a t e : f r e q u e n c y ( k i l o c y c l e s per second); I = impact; P = p u l s e ; PG = p u l s e group; PGI = p u l s e group i n t e r v a l ; P I = p u l s e i n t e r v a l ; MF = main f r e q u e n c y a r e a .  16  Temporal p a t t e r n o f p u l s e s : arrangement o f p u l s e s i n a complete s i g n a l ( a c c o r d i n g c a l l e d pulse  t o some a u t h o r s t h i s i s a l s o  modulation).  S i g n a l or c a l l : a complete s e t o f p u l s e s  o r p u l s e groups.  R e c o r d i n g o f t h e s t r i d u l a t o r y s i g n a l s was made both i n n a t u r a l h a b i t a t s and i n t h e l a b o r a t o r y . I n t h e l a b o r a t o r y s a t i s f a c t o r y recordings  c o u l d be made, p r o v i d i n g t h a t no  motors were used i n t h e same room. The bug c o n t a i n e r was i s o l a t e d from t h e g e n e r a l v i b r a t i o n s o f the b u i l d i n g by p l a c i n g i t on a 5 cm thick, foam rubber The  cushion.  problem o f p o s s i b l e sound changes i n l a b o r a t o r y  c o n d i t i o n s was s t u d i e d by a n a l y s i n g s i g n a l s r e c o r d e d i n several d i f f e r e n t containers. Glass,  b r i c k , s t y r o f o a m , and  s e v e r a l d i f f e r e n t p l a s t i c c o n t a i n e r s were t r i e d and a l l had an e f f e c t o f making one o r more f r e q u e n c y areas o f t h e sound stronger and  t h a n o t h e r s , o r c r e a t i n g harmonics. Wooden t r a y s  some s o f t p l a s t i c t r a y s and paper mugs were found t o  absorb almost a l l sounds thus making t h e s i g n a l s t o o f a i n t . The  o n l y c o n t a i n e r where t h e s i g n a l s were s i m i l a r t o those  r e c o r d e d i n n a t u r a l c o n d i t i o n s was a m e t a l c o t t a g e  bathtub  l i n e d i n t e r i o r l y a t t h e s i d e s and bottom w i t h a 5 - 1 0 cm t h i c k l a y e r o f f i n e g r a i n sand and w i t h some l a r g e r on t h e bottom- t h e best r e s u l t s were o b t a i n e d  rocks  when t h e bugs  were s i t t i n g on t h e rock w h i l e s t r i d u l a t i n g . To keep t h e bugs w i t h i n t h e a r e a a t which t h e r e c o r d i n g c o u l d be done s a t i s f a c t o r i l y , a fence made o f s o f t p l a s t i c s c r e e n was used.  17  The e f f e c t o f temperature on s t r i d u l a t i o n was s t u d i e d by r e c o r d i n g i n n a t u r a l c o n d i t i o n s , b a t h t u b , and c u l t u r e t r a y s . I t was shown t h a t a l t h o u g h t h e c u l t u r e t r a y s had some e f f e c t on t h e f r e q u e n c y of t h e sounds, t h i s d i d not a f f e c t t h e p u l s e t a t e , and t h e t r a y s c o u l d be used f o r t h i s study. Low temperatures i n t h e l a b o r a t o r y were o b t a i n e d by p l a c i n g g t h e t r a y s i n a c o n s t a n t temperature c a b i n e t a t 5°C f o r a few h o u r s , and h i g h temperatures were produced by p l a c i n g a 100 w a t t lamp above t h e t r a y s u n t i l the temperature was so h i g h t h a t t h e bugs d i d not s t r i d u l a t e any more. A f t e r t h e s e t r e a t m e n t s the temperature was a l l o w e d t o i n c r e a s e or decrease s l o w l y towards room t e m p e r a t u r e . The bugs were i n d u c e d t o s t r i d u l a t e a t d e s i r e d temperatures by p l a y i n g back t o them c e r t a i n s i g n a l s from p r e v i o u s r e c o r d i n g s and s i m u l t a n e o u s l y r e c o r d i n g a l l s i g n a l s w i t h a n o t h e r tape r e c o r d e r . The l o u d s p e a k e r used f o r t h e s e p l a y b a c k s was a Uher earphone p r o t e c t e d from w e t t i n g by a t h i n r u b b e r s l e e v e (condom). Graphs f o r t h e e f f e c t of temperature on p u l s e r a t e as w e l l as on p u l s e group r a t e were p l o t t e d and c a l c u l a t e d by computer ( B i o l o g y Data C e n t r e , I n s t i t u t e of A n i m a l Resource Ecology, U n i v e r s i t y of B r i t i s h Columbia). S t r i d u l a t o r y mechanism and movements i n v o l v e d i n t h e sound p r o d u c t i o n were observed w h i l e t h e bugs responded t o p l a y b a c k s i g n a l s . However, because t h e movements a r e r e l a t i v e l y f a s t , s a t i s f a c t o r y o b s e r v a t i o n s c o u l d be made o n l y a t low t e m p e r a t u r e s ( 1 0 - 1 5 ° C ) . Morphology  o f t h e s t r i d u l a t o r y a p p a r a t u s was  studied  18  by a mark. 2 A Cambridge S t e r e o s c a n e l e c t r o n microscope (Cambridge, E n g l a n d ) . S p e c i f i c d i f f e r e n c e s i n t h e s t r u c t u r e o f t h e p a r s s t r i d e n s and t h e p l e c t r u m a p p a r e n t l y c o r r e l a t e w i t h the loudness  of the s i g n a l s of v a r i o u s species ( c f .  M i t i s , 1 9 3 6 ) . However, no s u i t a b l e equipment was a v a i l a b l e f o r measuring t h e a m p l i t u d e o f the s i g n a l s and t h u s , t h e study o f t h e morphology o f t h e s t r i d u l a t o r y apparatus  was  r e s t r i c t e d t o the general s t r u c t u r e of the pars s t r i d e n s and t h e p l e c t r u m . The d i e l p e r i o d i c i t y o f t h e s t r i d u l a t i n g a c t i v i t y o f some s p e c i e s was i n v e s t i g a t e d i n t h e f i e l d . Recordings f o r f i v e minutes i n each hour were c a r r i e d over 24 hour p e r i o d s d u r i n g May and June 1969 a t Barnes Lake, Westwick Lake, and LB2.  L a b o r a t o r y o b s e r v a t i o n s on d i e l p e r i o d i c i t y o f t h e  s t r i d u l a t i n g a c t i v i t y i n a l l s p e c i e s were c a r r i e d out d u r i n g the s p r i n g and summer o f 1970. I n these experiments t h e bugs were p l a c e d i n c u l t u r e t r a y s which had been p a i n t e d g r e y om t h e s i d e s and bottom: i n t r a n s p a r e n t t r a y s t h e bugs tend t o swim f o r hours a g a i n s t t h e w a l l s . The t r a y s were kept u n d i s t u r b e d i n t h e l a b o r a t o r y a t r e l a t i v e l y temperature  constant  (20-24°C) and t h e bugs were p l a c e d i n them  24 hours p r i o r t o t h e b e g i n n i n g o f each experiment.  The  l i g h t c o n d i t i o n s were n a t u r a l except t h a t t h e t r a y s never r e c e i v e d d i r e c t s u n l i g h t and t h e room a p p a r e n t l y was always s l i g h t l y d a r k e r than i n d i r e c t l i g h t o u t d o o r s : no a r t i f i c i a l l i g h t was a l l o w e d i n t h e room d u r i n g t h e t e s t s .  Recordings  were made by c o n n e c t i n g t h e tape r e c o r d e r t o a time c l o c k s e t such t h a t t h e r e was a r e c o r d i n g f o r f i v e minutes every  hour over t h e f u l l 24 hour p e r i o d , and t h e t e s t s were r u n for  f i v e consecutive  days. The hydrophone was p l a c e d i n  the m i d d l e o f t h e t r a y and t h e t r a y was p o s i t i o n e d on a foam rubber  cushion.  4. B e h a v i o r The  b e h a v i o r a l r o l e o f s t r i d u l a t i o n was i n i t i a l l y  s t u d i e d by o b s e r v i n g  t h e bugs i n c u l t u r e t r a y s and i n t h e i r  n a t u r a l environment i n s h a l l o w water d u r i n g t h e summer o f 1969.  E x p e r i m e n t a l t e s t s i n t h e l a b o r a t o r y were c a r r i e d out  d u r i n g t h e s p r i n g and summer o f 1 9 7 0 . The  most d e t a i l e d a n a l y s i s o f t h e s t r i d u l a t o r y b e h a v i o r  was c a r r i e d out on C_. b i f i d a . The f i r s t t h o s e o f S c h a l l e r ( 1 9 5 1 ) and F i n k e  experiments  ( 1 9 6 8 ) by o b s e r v i n g and  q u a n t i f y i n g a l l a c t i v i t i e s of the experimental under v a r i o u s  specimens  c o n d i t i o n s . However, o n l y one o r two specimens  were t e s t e d a t one time, urbing  followed  i n order t o avoid p o s s i b l e  dist-  e f f e c t s o f l a r g e numbers on each o t h e r . F o r t h i s  a n a l y s i s , 200 specimens o f C_. b i f i d a were t a k e n from Lake Lye  i n l a t e A p r i l 1 9 7 0 and t r a n s p o r t e d  to the laboratory.  Because males were s t r i d u l a t i n g and a l s o c o p u l a t i o n a t t e m p t s were observed, t h e specimens were thought t o be r e a d y f o r the t e s t s . The f o l l o w i n g f o u r c u l t u r e s were ,-s.et u p 3 0  males  .20 males and 20 f e m a l e s ; 3 0 f e m a l e s ; 1 male. T e s t s were c a r r i e d out e v e r y second day u n t i l t h e 1 1 t h o r 1 3 t h day, and  t h e t e s t p e r i o d f o r each e x p e r i m e n t a l  15 m i n u t e s . The e x p e r i m e n t a l  c o n d i t i o n was  c o n d i t i o n s were: a l o n e ,  with  20  auditory, v i s u a l , or chemical s t i m u l i . I n order to provide n a t u r a l a u d i t o r y s t i m u l i , a s m a l l cage was made o f p l a s t i c s c r e e n , and 4 - 5 specimens  from t h e 3 0 male c u l t u r e were  p l a c e d i n t o t h i s cage which t h e n was p l a c e d i n t o t h e t r a y w i t h t h e e x p e r i m e n t a l a n i m a l s , i . e . t h e e x p e r i m e n t a l bugs c o u l d hear t h e s i g n a l s o f t h e specimens  i n t h e cage, but  c o u l d n o t t o u c h them. F o r v i s u a l s t i m u l i , a s m a l l w a t e r p r o o f c o n t a i n e r o f t r a n s p a r e n t p l a s t i c was made and t h e s t i m u l a t i n g specimen was p l a c e d i n t o t h i s c o n t a i n e r which t h e n was i n t r o d used t o t h e e x p e r i m e n t a l a n i m a l s . A l s o a dead p i n n e d was  specimen  t r i e d , i n t h i s case f i x e d a t t h e end o f a g l a s s r o d .  Chemical s t i m u l u s was p r o v i d e d by k e e p i n g two males from the 3 0 male c u l t u r e , o r two females from t h e 3 0 female c u l t u r e , , i n a t r a y f o r 3 - 4 hours and removing these  specimens  j u s t before i n t r o d u c i n g the experimental animals i n t o the tray. R e s u l t s o f t h e experiments were a n a l y s e d u s i n g t h e W i l c o x o n matched-pairs way  s i g n e d - r a n k s t e s t and Friedman two-  analysis of variance (Siegel,  1956).  When t h e t r u e response o f r e c e p t i v e CJ. b i f i d a  females  t o c o n s p e c i f i c male s i g n a l s was d i s c o v e r e d t h e b a s i s f o r f u r t h e r b e h a v i o r a l s t u d i e s was t o keep males and females o f e v e r y s p e c i e s i n s e p a r a t e c u l t u r e s thus p r e v e n t i n g a l l und e s i r e d c o p u l a t i o n s . The f u n c t i o n and t h e s i g n i f i c a n c e o f the s t r i d u l a t o r y s i g n a l s was t h e n t e s t e d by p l a y i n g back c o n s p e c i f i c male s i g n a l s t o a group o f females and t h e r e s p o n d i n g females were t r a n s f e r r e d t o another t r a y . The response o f t h e s e females was t h e n t e s t e d a g a i n s t a l l  21  p o s s i b l e C o r i x i d a e s i g n a l s , and f i n a l l y some males o f t h e i r own s p e c i e s were i n t r o d u c e d i n t o t h e same t r a y and c o p u l a t i o n b e h a v i o r was observed. A l s o t h e group o f females which d i d not respond t o c o n s p e c i f i c male s i g n a l s was observed i n t h e presence o f some males. By p l a y i n g back p r e v i o u s l y r e c o r d e d female s i g n a l s t h e males were i n d u c e d t o t r y t o c o p u l a t e , but the u n r e c e p t i v e females adopted a c e r t a i n r e l e a s e b e h a v i o r which c o u l d t h e n be s t u d i e d . A f t e r these t e s t s b o t h r e c e p t i v e and u n r e c e p t i v e females were p r e s e r v e d i n a l c o h o l and t h e i r gonad development was examined. P l a y b a c k experiments u t i l i s i n g a l l p o s s i b l e p r e v i o u s l y r e c o r d e d s i g n a l s were a l s o c a r r i e d out w i t h males o f each s p e c i e s o f t h e genus C e n o c o r i x a . I n these experiments t h e s t r i d u l a t o r y response o f v a r i o u s males was r e c o r d e d and o b s e r v a t i o n s o f t h e i r moving a c t i v i t i e s were made. I n t h e s p e c i e s r e c o g n i t i o n experiments  each s i g n a l was  p l a y e d f i v e times t o a group o f specimens ( u s u a l l y  five).  When a l l d i f f e r e n t s i g n a l s hadebeen p l a y e d back f i v e times the whole experiment was r e p e a t e d f i v e times ( t h u s t o t a l p l a y b a c k f o r each s i g n a l was 25 t i m e s ) . When specimens were t e s t e d a g a i n s t v a r i o u s s i g n a l s , t h e bugs were a l l o w e d f i v e seconds i n which t o answer, f o r a p o s i t i v e r e a c t i o n .  Another  f i v e seconds was a l l o w e d t o e l a p s e b e f o r e r e p e a t i n g t h e p l a y b a c k , but i f t h e t e s t a n i m a l s s t r i d u l a t e d d u r i n g t h i s l a t t e r f i v e second p e r i o d , t h e s i g n a l was n o t c o n s i d e r e d t o be a response t o t h e p l a y b a c k , and a f u r t h e r f i v e seconds was a l l o w e d t o e l a p s e b e f o r e t h e next p l a y b a c k . A l l o f these experiments were made a t room temperature  (21-24°C).  22 I n a l l playback, experiments t h e l o u d n e s s o f t h e s i g n a l s was  a d j u s t e d t o be as n a t u r a l as p o s s i b l e . The volume o f t h e  tape r e c o r d e r p l a y i n g t h e s i g n a l s back was a d j u s t e d by r e c o r d i n g w i t h a n o t h e r tape r e c o r d e r t h r o u g h t h e hydrophone. These experiments were c a r r i e d out i n t h e c u l t u r e t r a y s , u s i n g t h e earphone  as a l o u d s p e a k e r . However, owing t o  echoes i n t h e t r a y s t h e experiments on t h e d i s t a n c e f o r r e c o g n i t i o n o f s i g n a l s o f t h e o p p o s i t e sex were c a r r i e d out i n t h e sand l i n e d b a t h t u b , u s i n g an underwater  loud-  speaker model MM-2PPS ( U n i v e r s i t y Sound Co., Oklahoma C i t y , O k l a . ) . The r e s u l t s o f t h i s experiment were c o n f i r m e d w i t h some o f t h e s p e c i e s by p l a c i n g males and females i n s e p a r a t e s m a l l cages made o f p l a s t i c s c r e e n , and o b s e r v i n g t h e i r responses t o each o t h e r ' s s i g n a l s a t v a r i o u s d i s t a n c e s . The d e t a i l e d o b s e r v a t i o n s on a g o n i s t i c b e h a v i o r between males were a l s o made i n t h e b a t h t u b .  23  III.  RESULTS  1. Mechanism o f sound p r o d u c t i o n and morphology of the s t r i d u l a t o r y apparatus In  the genus C e n o c o r i x a  both males and females a r e  a b l e t o s t r i d u l a t e . Three d i f f e r e n t mechanisms o f sound p r o d u c t i o n were observed:  i ) By r u b b i n g a s e r i e s o f s p e c i a l  s t r i d u l a t o r y pegs ( p a r s s t r i d e n s ) , l o c a t e d a n t e r o b a s a l l y on the f o r e femora ( F i g . 2 ) , a g a i n s t the edge o f the maxi l l a r y p l a t e ( p l e c t r u m ) , l o c a t e d j u s t p o s t e r i o r l y t o the d o r s o l a t e r a l corner of the anteclypeus to  Parsons,  19^5] 1 9 6 6 ) ( F i g . 3 ) .  (terminology  according  i i ) By r u b b i n g the h i n d  l e g s a l t e r n a t e l y or t o g e t h e r a g a i n s t the f o l d e d f o r e wings l y i n g above t h e abdomen, or a g a i n s t the v e n t r a l s i d e o f abdomen and e x t e r n a l g e n i t a l i a . s t r i d u l a t o r y sounds were r e c o r d e d  i i i ) I n two s p e c i e s f a i n t a t the b e g i n n i n g  of  s u c c e s s f u l c o p u l a t i o n , but the o r i g i n o f t h e s e sounds c o u l d not be d e t e c t e d . The f i r s t c a t e g o r y I s c l e a r l y t r u e s i g n a l l i n g i n t h a t the movement i s made s p e c i f i c a l l y f o r sound p r o d u c t i o n .  The  second c a t e g o r y seems t o belong t o sounds produced as a byproduct  o f some a c t i v i t y , the prime a c t i o n o f w h i c h i s not  sound p r o d u c t i o n , but one o f c l e a n i n g o r t h e l i k e . The  third  c a t e g o r y might be j u s t sound produced as a r e s u l t o f f r i c t i o n between the two specimens, but a l t e r n a t i v e l y i t might as w e l l be an i m p o r t a n t  signal.'^for a s u c c e s s f u l c o p u l a t i o n . However,  i t cannot be c l a s s i f i e d owing t o the f a c t t h a t the source the sound i s unknown.  of  24  F i g . 2. S t e r e o s c a n photograph of the f r o n t l e g of _6. b l a i s d e l l i male showing the l o c a t i o n of the pars s t r i d e n s ( p s ) . • M a g n i f i c a t i o n xlOO.  F i g . 3 - S t e r e o s c a n photograph of the head o f C. b l a i s d e l l i female showing the l o c a t i o n of the p l e c t r u m ( p ) . F r o n t o l a t e r a l view, m a g n i f i c a t i o n x50.  26 The t r u e s t r i d u l a t o r y s i g n a l s i n the f i r s t  category  c o n s i s t o f a s e r i e s o f p u l s e s , each p u l s e b e i n g a f o r w a r d push o f one l e g . When the l e g i s moved backwards i t does not t o u c h the p l e c t r u m . However, u s u a l l y the o t h e r l e g i s pushed f o r w a r d s a t the same t i m e , i . e . e v e r y second p u l s e i s produced l e g s was  by one l e g . The a l t e r n a t e movement,"of the f r o n t  the o n l y way t h a t both males and females were  observed t o produce these s i g n a l s , r e g a r d l e s s of the p u l s e r a t e or the t e m p o r a l p a t t e r n o f p u l s e s -in the s i g n a l s . The s t u d y o f the morphology o f the s t r i d u l a t o r y showed t h a t g e n e r a l l y the males have more pegs and  apparatus  thicker  pegs on the p a r s s t r i d e n s t h a n the females ( T a b l e I , F i g . 4 ) . A l s o the s i z e of the p l e c t r u m i s d i f f e r e n t i n the two  sexes:  the m a x i l l a r y p l a t e of the males i s g e n e r a l l y l a r g e r t h a n t h a t o f the females ( F i g . 4 ) . A l t h o u g h no equipment was a v a i l a b l e f o r a c t u a l meas-^ urement o f the loudness o f the s i g n a l s , s u b j e c t i v e o b s e r v a t i o n s i n d i c a t e c l e a r d i f f e r e n c e s between the s p e c i e s . I n a d d i t i o n , i n each s p e c i e s the male c a l l always  appears  l o u d e r t h a n the female c a l l . A c o r r e l a t i o n i s suggested between the l o u d n e s s of the s i g n a l s and the t h i c k n e s s of the pegs of the pars s t r i d e n s . However, the s t r u c t u r e o f the p a r s s t r i d e n s may  not be the o n l y f a c t o r a f f e c t i n g the  a m p l i t u d e o f the sound:  the s i z e o f the p l e c t r u m was  observed t o be d i f f e r e n t i n the two sexes..  also  27 Table I . T h i c k n e s s o f the pegs o f the p a r s s t r i d e n s (average from 1 0 specimens)- and comparison of the number o f peg rows on the pars s t r i d e n s ( 1 0 specimens) and the number o f impacts per p u l s e (mean + s t a n d a r d e r r o r ; number o f specimens as i n Table I I ) . I n s e v e r a l s p e c i e s the males a r e a b l e t o produce "slow" and " f a s t " p u l s e s i n t h e i r s i g n a l s : the number o f imp a c t s p e r p u l s e i n these d i f f e r e n t p u l s e s are i n d i c a t e d by s and f , r e s p e c t i v e l y . * - no s i g n a l s r e c o r d e d . The o r d e r o f the s p e c i e s i s a c c o r d i n g t o data c o n t a i n e d I n Appendix I . Species/sex  Number o f peg rows on pars s t r i d e n s  Number of impacts per pulse 9.04 + 0.29 6.64 + 0.30  b i f i d a o*  pars s t r i d e n s , t h i c k n e s s of pegs (mm) .0056  bifida ?  . 0040  .15-18 8-12  k u i t e r t i o* kuiterti ?  .0046 .0018  13-15 6- 9  a n d e r s o n i o* andersoni ?  .0065 .0029  10-13 7- 9  s 4.56 + 0.14 f 3.27 + 0.08 1.68 + 0.06  u t a h e n s i s o* utahensis $  . OO58  10-12 7- 8  s 5.56 + 0.18 f 2.88 + 0.09 4.63 + 0.14  d a k o t e n s i s o* dakotensis $  .OO59  .0029  11-14 8-12  8.08 + 0.31 5.39 + 0.22  b l a i s d e l l i o* blaisdelli $  . 0081 . 0030  1 1 - 14 8- 1 2  s 8.05 + 0.24 f 4.82 + 0.18 7.92 + 0.23  w i l e y a e o*  .0062  wileyae ?  .0033  13-15 9- 1 2  slO.72 + 0.35 f 3.96 + 0.14 6.97 + 0.30  e x p l e t a o* expleta ?  .0093 .0050  15-17 12- 16  6.26 + 0.18 7.05 + 0.22  .0021  s 7.58 + 0.18 f 4.35 ± 0.13  28  F i g . 4 . S t e r e o s c a n photographs of the s t r i d u l a t o r y apparatus of £. b l a i s d e l l i . A = male p l e c t r u m ; B * male p a r s s t r i d e n s , pegs; C = female p l e c t r u m ; D = female p a r s s t r i d e n s , pegs. M a g n i f i c a t i o n s : p l e c t r u m x 2 0 0 , p a r s s t r i d e n s xlOOO.  2. Audiospectrographic a)  a n a l y s i s o f the s t r i d u l a t o r y s i g n a l s  General The  s t r i d u l a t o r y s i g n a l s of the v a r i o u s s p e c i e s of  Cenocorixa. are s p e c i e s s p e c i f i c . The most c o n s t a n t  character  i s the temporal p a t t e r n of p u l s e s . F u r t h e r s p e c i f i c  diff-  erences are found i n the s t r u c t u r e o f p u l s e s , i n the p u l s e r a t e , and i n the s i g n a l l e n g t h .  The  s i g n a l s of the  two  sexes are a l s o d i f f e r e n t . Cenocorixa  females are a b l e to produce o n l y .one  kind  o f s i g n a l per s p e c i e s , w h i l e i n the males o f s e v e r a l s p e c i e s the s i g n a l i s composed o f two d i s t i n c t l y d i f f e r e n t p a r t s . J i n some cases'Jthese p a r t s can be produced s e p a r a t e l y ; these males are thus a b l e t o produce two d i f f e r e n t  signals.  I n the s t r i d u l a t i o n the s i g n a l s a r e composed o f s e v e r a l p u l s e s , and f u r t h e r , each p u l s e c o n s i s t s of s e v e r a l impacts. Thus the sound i s not c o n t i n u o u s ,  but even w i t h i n the p u l s e s  i t i s b u i l t up o f s h o r t c y c l e s each f o l l o w e d by a s h o r t i n t e r v a l . Length o f the i n t e r v a l s between two impacts v a r y between the s p e c i e s and  consecutive  between d i f f e r e n t p a r t s  o f the s i g n a l s , and i n some cases even w i t h i n a s i n g l e p u l s e . I t i s a l s o a f f e c t e d by temperature:  the h i g h e r the temperature  the s h o r t e r the i n t e r v a l . T h i s c l e a r l y c o r r e l a t e s w i t h the speed used t o draw the pars s t r i d e n s over the p l e c t r u m ,  and  thus i t i s apparent t h a t each impact r e p r e s e n t s a s t r i k e of one peg row of the pars s t r i d e n s on the p l e c t r u m .  However,  the number of peg rows of the pars s t r i d e n s i s always more t h a n the average number o f impacts per p u l s e (Table It):  the  bugs do not seem t o use the whole p a r s s t r i d e n s i n p r o d u c i n g  30 the sounds. Table I I r e c o r d s t h e main f r e q u e n c y a r e a s , average numbers o f p u l s e s p e r s i g n a l s , and t h e numbers o f p u l s e groups p e r s i g n a l s i n t h e v a r i o u s s p e c i e s . From t h e s e d a t a the f o l l o w i n g g e n e r a l i z a t i o n s can be made: i ) The f r e q u e n c y o f t h e sound i s a p p r o x i m a t e l y t h e same i n a l l s p e c i e s and sexes. i i ) Female s i g n a l s u s u a l l y i n c l u d e more p u l s e s p e r c a l l than comparable male s i g n a l s and c o n s e q u e n t l y , t h e d u r a t i o n o f t h e female s i g n a l s i s u s u a l l y l o n g e r than t h a t of t h e male s i g n a l s . i i i ) The male s i g n a l s a r e u s u a l l y more c o m p l i c a t e d t h a n t h e comparable female  signals.  Concerning t h e numbers o f i n d i v i d u a l s used and t h e numbers o f s i g n a l s a n a l y s e d f o r t h e i n f o r m a t i o n i n t h e Table I I , i t s h o u l d be noted t h a t r e c o r d i n g s were made when a number o f i n d i v i d u a l s was i n a c u l t u r e t r a y o r i n the sand l i n e d bathtub, but i t i s n o t known how many s i g n a l s from each i n d i v i d u a l was a n a l y s e d . However, each i n d i v i d u a l was t e s t e d p r i o r t o t h e r e c o r d i n g s so t h a t a l l i n s e c t s were known t o be i n normal s t r i d u l a t o r y c o n d i t i o n . T h i s e x p e r i m e n t a l procedure  i s considered meaningful, since the s i g n i f i c a n c e of  s t r i d u l a t i o n concerns more t h e s p e c i e s than t h e i n d i v i d u a l s , i . e . t h e s i g n a l s a r e s p e c i e s s p e c i f i c , but not i n d i v i d u a l l y different.  31 Table I I . Numerical c h a r a c t e r i s t i c s  o f Cenocorixa  s i g n a l s . Symbols: * = s i g n a l composed of one p u l s e group  (number o f p u l s e s p e r p u l s e group = number o f p u l s e s per s i g n a l ) ;  $ = a l l p u l s e groups a r e s i m i l a r ,(sub-  s e q u e n t groups,. = the f i r s t group). Species/sex  J  Number o f specimens p r e s e n t at recording  Number o f signals analysed  Main frequency area (kc/sec)  Average number of pulses/signal + standard e r r o r  Number o f pulse groups per s i g n a l  b i f i d a d*  10 5  3-4.5 3-4.5  19-57 + 0.59 21.92 + 0.87  1  bifida ?  75 36  10  72  3-4.5  15.03  10  3- 5 4- 5  3 0 . 0 8 + 1.36  51.63  85.26 + 3 . 3 ^  k u i t e r t i 0* o*  Number o f p u l s e s p e r p u l s e group First  group  Subsequent groups  1  + O.56  11.20+1.33  13.27+1.11  9.19 + 0.89 28.85 + 1.11  20.81 + 1.33 *  46.50 + 3 . 6 6  38.79 + 1 - 6 8  andersoni ?  3  52 20  u t a h e n s i s o*  3  34  3-5  utahensis $  2  19  3-5  10  52 30  4-5  23.83 + 0.81  1  3-5  21.89 + 1.85  i  4-5 3-5  17.75 ± 1.42 28.70 + 1.94.  5.62 + 0.^2 , 13.08 + 1 . 2 4 1.00 + 0 . 0 0 1 '• * • . *  3.5-5 3-4  36.03 + 1.07 52.66 + 3.71  9.25 + 0.30  28.05 + 1.52  6.41  +  64.43  8.85-  +  andersoni  dakotensis  0*  dakotensis $  4  blaisdelli  cf  10  blaisdelli  ?  4  37 30  w i l e y a e 0*  10.  32  wileyae ?  5  e x p l e t a o*  10  expleta ?  3  41  38 14  3-5 . 2.5-3.5  100.21  +  4.13  + 3 . 4 0  +  8.63  1.75  + 0 . 1 4  2  1  *  9.42  + 0 . 4 5  0.30  9 . 8 4  +  1.28  7.28 +  2.5.5 + 0.03  1  0.72 0.48  4.47  + 0 . 2 4  32 b) D e s c r i p t i o n o f t h e s i g n a l s C_. b i f i d a (Hungerford)  ( F i g . 5):  Male c a l l : Recorded between  8.0 - 28.8°C.  I n the  e x p e r i m e n t a l c o n d i t i o n s no s i g n a l s were o b t a i n e d a t or below, o r a t  7.0°C  30.0°C o r above. The s i g n a l i s o f s i m p l e  m u l t i p u l s a t e type w i t h c l e a r and even p u l s e Female c a l l : Recorded a t  21.0 - 24.7°C  intervals*. o n l y , but tem-  p e r a t u r e l i m i t s f o r females t o produce s i g n a l s a r e p r o b a b l y the same as f o r males. The s i g n a l i s v e r y much l i k e t h a t o f the.male, but w i t h fewer impacts p e r p u l s e and much lower amplitude*. C_. k u i t e r t i Hungerford  (Fig. 6):  Male c a l l : Recorded between  15.0 - 28.0°C,  but i t i s  p r o b a b l e t h a t t h e lower l i m i t f o r s t r i d u l a t i o n o f t h i s i s below  species  15.0°C. The s i g n a l o f _C. k u i t e r t i male i s more com-  p l i c a t e d t h a n t h a t o f C_. b i f i d a , and two d i f f e r e n t p u l s e groups were observed:  i ) a group o f "slow" p u l s e s which r e e -  semble t h e c a l l o f C_. b i f i d a , b u t t h e p u l s e s f o l l o w each oj'her w i t h v e r y s h o r t p u l s e i n t e r v a l s and thus a r e almost f u s e d t o g e t h e r , and i i ) a group o f " f a s t " p u l s e s i n which the p u l s e s a r e much s h o r t e r than t h e slow p u l s e s , b u t f o l l o w each o t h e r w i t h more o r l e s s i r r e g u l a r , but d i s t i n c t  intervals.  S t r u c t u r a l l y t h e f a s t p u l s e s i n c l u d e l e s s impacts t h a n t h e slow ones*. The s i g n a l may be composed o f slow p u l s e s a l o n e , or b o t h types t o g e t h e r . I f i t i s composed o f b o t h types t h e slow p u l s e s a r e always i n t h e b e g i n n i n g . The t r a n s i t i o n from  * Numerical and I I .  d a t a on s i g n a l s o f each s p e c i e s a r e i n Tables I  33  the slow p u l s e s t o the f a s t ones i s u s u a l l y g r a d u a l . Female c a l l : Never r e c o r d e d the bugs were observed  s a t i s f a c t o r i l y . Occasionally  to perform  s t r i d u l a t o r y movements  w i t h t h e i r f r o n t l e g s , but a p p a r e n t l y the a m p l i t u d e s i g n a l s was  o f these  too low f o r the equipment used. A c c o r d i n g t o the  s t r i d u l a t o r y movements the s i g n a l s p r o b a b l y are of  simple  m u l t i p u l s a t e type. C_. a n d e r s o n i Hungerford  (Fig. 7) '  Male c a l l : Recorded between 12.0 - 28.0°C, but the l i m i t may  be below the observed  one.  lower  U s u a l l y the s i g n a l i s  composed o f two p u l s e groups ( l i k e t h a t o f _C. k u i t e r t i ) : slow p u l s a t e d b e g i n n i n g and f a s t p u l s a t e d end.  a  Sometimes  the f i r s t p u l s e group i s produced a l o n e . P u l s e s o f the  first  group are somewhat i r r e g u l a r and w i t h s h o r t i n t e r v a l s ,  but  the p u l s e s o f the second group are r e g u l a r and w i t h d i s t i n c t i n t e r v a l s . The  t r a n s i t i o n from the slow p u l s e s t o the  fast  ones i s a b r u p t . Female c a l l : Recorded between 21.5 - 26.2°C, but temp e r a t u r e l i m i t s are p r o b a b l y the same f o r both sexes. s i g n a l i s composed o f 1-3  The  s i m p l e m u l t i p u l s a t e , somewhat  i r r e g u l a r p u l s e groups. The p u l s e group i n t e r v a l s were always 1-2  seconds and d i d not seem t o be a f f e c t e d by tem-  p e r a t u r e . P u l s e i n t e r v a l s a r e d i s t i n c t and the number of impacts p e r p u l s e i n _C. a n d e r s o n i female i s l e s s t h a n i n any o t h e r s p e c i e s .  34 C_. u t a h e n s i s (Hungerford)  (Fig.  Male c a l l : Recorded between ear t h i s c a l l  11.7  8):  - 28.0°C.  sounds v e r y much l i k e the c a l l  To the human  o f C_. a n d e r s o n i  male, but both the slow and the f a s t p u l s e groups are siderably  l o n g e r i n _C. u t a h e n s i s . The  spectrogram  con-  a l s o shows  t h a t the p u l s e s of the slow p u l s e group are not a l l s i m i l a r , but a p p r o x i m a t e l y every second p u l s e i s s h o r t e r i n d u r a t i o n ( a l m o s t l i k e the p u l s e s of the f a s t p u l s e g r o u p ) . e n s i s , as i n C.  I n _C. u t a h -  a n d e r s o n i , the slow p u l s e group may  be p r o d -  uced a l o n e . I n a complete s i g n a l the t r a n s i t i o n from the  slow  p u l s e s t o the f a s t ones i s abrupt. Female c a l l : Recorded between  21.5 - 23.4°C,  but tem-  p e r a t u r e l i m i t s are p r o b a b l y the same as f o r the o p p o s i t e sex. The  s i g n a l i s somewhat i r r e g u l a r being a simple  multi-  pulsate c a l l with d i s t i n c t pulse i n t e r v a l s . C_. d a k o t e n s i s (Hungerford)  (Fig. 9 ) :  Male c a l l : Recorded between  15.0 - 27.4°C.  The  signal  i s composed of g r a d u a l l y changing p u l s e s : a t the v e r y b e g i n n i n g the p u l s e s are r e l a t i v e l y l o n g and w i t h o u t  clear  i n t e r v a l s , but towards the end of the s i g n a l the p u l s e s become s h o r t e r and the p u l s e i n t e r v a l s become l o n g e r .  The  v e r y f i r s t p u l s e s c o n t a i n more  are  peg rows i n the p a r s s t r i d e n s :  impacts  than  there  i t i s p r o b a b l e t h a t these  p u l s e s a r e produced by back and f o r t h movement of the pars stridens  so t h a t the s t r i d u l a t o r y pegs t o u c h the p l e c t r u m  when the f r o n t l e g i s drawn backwards and when i t i s pushed f o r w a r d s , w h i l e i n . o t h e r p u l s e s the sound i s produced  35  o n l y when the l e g i s pushed  forwards.  Female c a l l : Recorded between 20.0  - 24.9°C, but  p r o b a b l y produced i n same temperature range as the male call.  The  s i g n a l resembles v e r y much the male c a l l ,  but  has almost even p u l s e r a t e t h r o u g h o u t the s i g n a l , and v e r y f i r s t p u l s e s c o n t a i n l e s s impacts  the  than the subsequent  pulses. _C. b l a i s d e l l i  (Hungerford) ( F i g .  Male c a l l : Recorded between  10):  7.0 - 28.8°C.  The  signal  i s composed o f two d i f f e r e n t p a r t s , b o t h o f which may produced c o m p l e t e l y i n d e p e n d e n t l y  be  from each o t h e r , but w h i c h  u s u a l l y are produced as f o l l o w s : a simple m u l t i p u l s a t e p u l s e group w i t h somewhat i r r e g u l a r p u l s e i n t e r v a l s , f o l l o w e d by s i n g l e , v e r y f a s t p u l s e s w i t h c o n s i d e r a b l y l o n g and  often  i r r e g u l a r i n t e r v a l s . T h i s second p a r t i s h e n c e f o r t h cons i d e r e d t o be composed o f " u n i p u l s a t e d p u l s e groups" ( c f . _C. w i l e y a e and _C. e x p l e t a ) . Female c a l l : Recorded between  22.2 - 27.2°C.  The  signal  resembles v e r y much the C_. b i f i d a c a l l . However, o n l y p a r t o f the _C. b l a i s d e l l i female c a l l i s composed o f r e g u l a r l y r e p e a t e d p u l s e s , p a r t of i t being more or l e s s Mounting s i g n a l ' ( F i g . 11): was  observed  irregular.  An odd s t r i d u l a t o r y  signal  always d u r i n g the f i r s t few seconds o f a  s u c c e s s f u l c o p u l a t i o n . O r i g i n o f the sound i s unknown. At  22.8°C t h i s s i g n a l was composed of s i x somewhat i r r e g u l a r  p u l s e groups and the whole s i g n a l l a s t e d about f i v e seconds (the  c o p u l a t i o n l a s t e d much l o n g e r , but no sounds were  r e c o r d e d a f t e r t h e f i r s t f i v e seconds). The main frequencya r e a seems t o be about 3 - 5 kc/sec  ( r e c o r d i n g made i n a  c u l t u r e t r a y ) . P u l s e r a t e i s about 2 4 p u l s e s p e r second at  22.8°C; t h i s i s n e a r l y twice the pulse r a t e of the  f i r s t p u l s e group o f t h e normal male c a l l ,  o r a female  call. _C. w i l e y a e (Hungerford) ( F i g . 1 2 ) : Male c a l l : Recorded between 5 . ^ - 2 8 . 2 ° C . The s i g n a l i s u s u a l l y composed o f two p a r t s : f i r s t a s i m p l e m u l t i p u l s a t e p u l s e group w i t h slow p u l s e s and s h o r t o r n o n - e x i s t i n g p u l s e i n t e r v a l s , t h e n s e v e r a l v e r y s h o r t groups o f f a s t p u l s e s w i t h c l e a r p u l s e i n t e r v a l s and r e g u l a r p u l s e group i n t e r v a l s . O c c a s i o n a l l y one p a r t o f t h e s i g n a l i s produced alone. Female c a l l : Recorded between 1 3 . 6 - 2 2 . 9 ° C , b u t temp e r a t u r e l i m i t s a r e p r o b a b l y c l o s e r t o t h e male l i m i t s . The s i g n a l i s v e r y r e g u l a r and a s i m p l e m u l t i p u l s a t e c a l l w i t h d i s t i n c t pulse  intervals.  _C. expleta. ( U h l e r ) ( F i g . 1 3 ) : Male c a l l : Recorded between 8 . 0 - 3 1 . 0 ° C . The s i g n a l i s composed o f s e v e r a l p u l s e groups, t h e f i r s t one b e i n g the f a i n t e s t i n a m p l i t u d e and w i t h t h e s l o w e s t p u l s e r a t e , the subsequent p u l s e groups a r e l o u d e r and w i t h f a s t e r p u l s e r a t e , i . e . t h e whole s i g n a l a c c e l e r a t e s i n b o t h ampl i t u d e and p u l s e r a t e . The p u l s e i n t e r v a l s a r e d i s t i n c t , but sometimes more o r l e s s i r r e g u l a r , and t h e p u l s e group i n t e r v a l s a r e somewhat i r r e g u l a r .  Female c a l l : Recorded  between 22.4 - 22.8 C o n l y , but  temperature l i m i t s a r e p r o b a b l y t h e same as i n t h e o p p o s i t e sex. The s i g n a l i s composed o f d i s t i n c t l y s e p a r a t e p u l s e s a r r a n g e d i n s e v e r a l p u l s e groups, thus r e s e m b l i n g t h e male call.  However, t h e female s i g n a l i s much l o w e r i n a m p l i t u d e  and l o n g e r i n d u r a t i o n t h a n t h e male s i g n a l , and i t does not a c c e l e r a t e i n a m p l i t u d e o r i n p u l s e r a t e . Mounting  s i g n a l : D u r i n g t h e f i r s t few seconds o f  s u c c e s s f u l c o p u l a t i o n s some f a i n t s t r i d u l a t o r y  signals  were observed. However, no s a t i s f a c t o r y r e c o r d i n g s were o b t a i n e d s i n c e t h e a m p l i t u d e o f t h e s e sounds was t o o l o w for  t h e equipment used. To t h e human e a r t h e s i g n a l s  sounded v e r y much l i k e t h e mounting s i g n a l s o f C_. b l a i s delli.  38 a  F i g . 5. Sound spectrograms of C_. b i f i d a s i g n a l s . A = male s i g n a l ; B = female s i g n a l ; C = d e t a i l s o f male s i g n a l ( p u l s e s 10-15 i n A ) ; D = d e t a i l s of female s i g n a l ( p u l s e s 7-11 i n B ) . Recorded a t 21.3°C. Specimens from B r i t i s h Columbia, C h i l c o t i n , B e e c h e s 1  P r a i r i e , Lake Lye.  F i g . 6. Sound spectrograms o f _C. k u i t e r t i s i g n a l s . A = male s i g n a l w i t h slow p u l s e s a l o n e ; B = complete male s i g n a l ; C = a male s i g n a l w i t h second p a r t d o m i n a t i n g ; D = d e t a i l s of male s i g n a l ( p u l s e s o f A ) . Recorded a t 21.9°C. Specimens from C a l i f o r n i a , Tuolumne Co., T i o g a Pas s.  KILOCYCLES w  W O W  KILOCYCLES  SECOND Cn  H>  W  o  W O W  W  SECOND  w  W  P-»  W  W  W  "•>li..  'Mr  I  CO H O O D CO  NH  N  co H O  NH  .  o » z  d  co OH  co  39 a  F i g . 7- Sound spectrograms of C_. a n d e r s o n i s i g n a l s . A = complete male s i g n a l ; B = male s i g n a l w i t h slow p u l s e s a l o n e ; C = female s i g n a l ; D = d e t a i l s of male s i g n a l ( f r o m the m i d d l e of A ) ; E = d e t a i l s of female s i g n a l ( from the m i d d l e of the f i r s t p u l s e group i n C). Recorded a t 2 2 . 4 ° C . Specimens.from Washington, Whatcom Co., C u s t e r .  F i g . 8. Sound spectrograms of C_. u t a h e n s i s s i g n a l s . A = complete male s i g n a l (a male s i g n a l w i t h the slow p u l s e s a l o n e i s s i m i l a r t o the f i r s t p u l s e group of the complete s i g n a l ) ; B = female s i g n a l ; C = d e t a i l s o f male s i g n a l (end of the f i r s t and b e g i n n i n g of the 'second p u l s e g r o u p ' i n A ) ; D = d e t a i l s of female s i g n a l ( p u l s e s 9 - l 8 °f B ) . Recorded a t 22.1°C. Specimens from A l b e r t a , M e d i c i n e Hat.  39 b  O  l—  'O  r-  2  u H  5-|  w  3  g  o o  1  i-J  1 5 -D  M  lO  w  E  5-  •mi- i in  <i  ill  l  i | M M •6  I  I  14  12  -8 SECONDS  5-  liiiiiiHiilf^'liiiiillii  3  p i& o  u  CC  2 B  ta .>  •!!!!>  'S 8  ;o •J  1  15  IH  10-  i!  ' '|1  Nil  •4  •6  -8  10 :  1-2  Hi  i i<l  14  SECONDS  8  40 a  F i g . 9 - Sound spectrograms of C_. d a k o t e n s i s s i g n a l s . A = male s i g n a l ; B = female s i g n a l ; C = d e t a i l s of male s i g n a l ( p u l s e s 4 - 1 2 of A ) ; D = d e t a i l s of female s i g n a l ( p u l s e s 1-3 and 7 of B ) . Recorded a t 2 1 . 0 °C. Specimens from A l b e r t a , Brooks.  F i g . 1 0 . Sound spectrograms of _C. b l a i s d e l l i s i g n a l s . A = male s i g n a l (note the u n i p u l s a t e ' c l i c k s ' a f t e r the m u l t . i p u l s a t e b e g i n n i n g ) ; B = female s i g n a l ; C = d e t a i l s of male s i g n a l ( p u l s e s 5 - 7 of the f i r s t p u l s e group and the f i r s t ' c l i c k ! of A ) ; D = d e t a i l s of female s i g n a l ( p u l s e s 6 - 1 3 of B ) . Recorded a t 2 2 . 4 ° C . Specimens from B r i t i s h Columbia, Vancouver, P o i n t Grey.  KILOCYCLES, W  O  W  ^  CO  KILOCYCLES  SECOND i  W  -  C  O  W  W  O  W  CO  SECOND W  i->  CO  W  N  . see  as"  co  10-  CO M  M O O ci-  o  g db  SS d co  d  co CO-'  •- -  vflfe.  co-  CO-  C0-  CD -t=r  o  «3  !  8  l  I  ' SECONDS  5"  F i g . 11. Sound spectrogram of CJ. b l a i s d e l l i mounting s i g n a l . The s i g n a l was r e c o r d e d d u r i n g the f i r s t few seconds of a s u c c e s s f u l c o p u l a t i o n a t 22.8 °C. The f i r s t two p u l s e s a t the l e f t are the l a s t p u l s e s of female s i g n a l , t h e n one u n i p u l s a t e 'click.' of the male, and the sounds produced d u r i n g the copul a t i o n begin j u s t before the one second mark. Specimens from B r i t i s h Columbia, Vancouver, P o i n t Grey.  4=H  42  a  F i g . 12. Sound spectrograms of C_. w i l e y a e s i g n a l s . A = male s i g n a l ; B = female s i g n a l ; C = d e t a i l s of male s i g n a l ( t h e f i r s t and the t h i r d p u l s e group of A ) ; D = d e t a i l s of female s i g n a l ( p a r t of B from the m i d d l e of the s i g n a l ) . Recorded a t 21.9 °C. Specimens from C a l i f o r n i a , L a s s e n Co., S a i d Lake.  F i g . 13- Sound spectrograms of C_. e x p l e t a s i g n a l s . A = male s i g n a l ; B = female s i g n a l ( o n l y p a r t of the s i g n a l i s shown: whole s i g n a l i n c l u d e d seven p u l s e g r o u p s ) ; C = d e t a i l s of male s i g n a l ( t h i r d p u l s e group of A ) ; D = d e t a i l s of female s i g n a l ( t h e l a s t f o u r p u l s e s of the second p u l s e group i n B ) . Recorded a t 22.3 °C. S p e c i m e n s f r o m B r i t i s h Columbia, Kamloops (LB2). (  K I L O C Y C L E S ^ SECOND  K I L O C Y C L E S , SECOND cn I  o .1  St  Ki  I  12..  am. Ml.  lo-  09 H O  g db r*.VM.,-.  O CO  co-  (0  Cn  H>  43 c) E f f e c t o f temperature on s t r i d u l a t i o n I n C o r i x i d a e , as i n a l l p o i k i l o t h e r m s , temperature a f f e c t s a l l body a c t i v i t i e s , i n c l u d i n g speed o f movements; upper and l o w e r l i m i t s on the body f u n c t i o n s a l s o e x i s t . S i n c e s t r i d u l a t i o n i s produced by movements o f the f r o n t l e g s , i t i s a f f e c t e d by temperature. However, the t e m p o r a l p a t t e r n o f p u l s e s and the number o f p u l s e s p e r s i g n a l a r e c o n s t a n t i n each s p e c i e s r e g a r d l e s s o f temperature  (except  i n some cases c l o s e t o temperature e x t r e m e s ) . Thus, the parameters a f f e c t e d by temperature a r e the d u r a t i o n o f the s i g n a l s and the p u l s e r a t e i n the s i g n a l s . The o n l y s p e c i e s where the change i n temperature changed the t e m p o r a l p a t t e r n o f p u l s e s was  C_. u t a h e n s i s , and  o c c u r r e d a t temperature extremes: above  this  27.5°C and below  13.0°C the specimens t e s t e d were a b l e t o produce o n l y slow p u l s e s , i . e . f a s t s t r i d u l a t i o n was i n h i b i t e d . The  normal  s i g n a l o f t h i s s p e c i e s i s composed o f b o t h a slow p u l s e group and a f a s t p u l s e F i g s . 14-16  group.  show the average d u r a t i o n o f the s i g n a l s  i n v a r i o u s s p e c i e s a t d i f f e r e n t t e m p e r a t u r e s . I t i s seen t h a t the curve w i t h s i g n a l l e n g t h p l o t t e d a g a i n s t temperature has a h y p e r b o l i c shape. D e p a r t u r e s from t h i s were observed o n l y when s t r i d u l a t i o n was r e c o r d e d c l o s e t o the temperature extremes  ( F i g . 16:  C_. w i l e y a e s i g n a l s a t the l o w e s t tem-  p e r a t u r e and C. e x p l e t a s i g n a l s a t the h i g h e s t  temperatures).  A graph w i t h i n c r e a s e I n p u l s e r a t e p l o t t e d a g a i n s t temperature forms a s t r a i g h t l i n e ( l i n e a r r e g r e s s i o n ) ( F i g s .  17-26).  I n cases where a s i g n a l i s composed o f p u l s e  groups  the temperature a f f e c t s both the p u l s e r a t e w i t h i n t h p u l s e groups ( F i g s . 24 and 2 6 ) and the r e p e t i t i o n r a t o f the p u l s e groups ( F i g s .  27-29).  4  5  8n  To  20 Temperature ( ° C )  F i g . 14. E f f e c t o f temperature on s i g n a l d u r a t i o n  30  i n £. b i f i d a  ( A ) , C_. k u i t e r t i ( B ) , and C_. a n d e r s o n i ( C ) . Symbols:  closed  c i r c l e s = male s i g n a l s ; open c i r c l e s = female s i g n a l s . Standard e r r o r s i n d i c a t e d by v e r t i c a l l i n e s ( l e s s t h a n 0.1 second s t a n d a r d e r r o r f a l l s w i t h i n the s i g n o f the symbol u s e d ) . Curves f i t t e d by eye o n l y on male s i g n a l s .  4 6  n  10  1  1  20  30  Temperature F i g . 15.  (°C)  E f f e c t o f temperature on s i g n a l d u r a t i o n i n CJ. u t a -  h e n s i s ( A ) , CJ. d a k o t e n s i s ( B ) , and (J_. b l a i s d e l l i ( C ) . I n CJ. b l a i s d e l l i male s i g n a l s  o n l y t h e f i r s t p u l s e group o f t h e  s i g n a l s i s concerned. Symbols as i n F i g . 1 4 .  Kl  a  F i g . 1 6 . E f f e c t of temperature on s i g n a l d u r a t i o n i n C. w i l e y a e  14.  (A) and CJ. e x p l e t a ( B ) . Symbols as i n F i g .  48  25-0_ -0-7G5B  +  04GG3X  N  =  78  20»0 15-0 10-01 5-0 U UJ  0-0 o.o  5.0  10» 0  15»0  20»0  25-0  30»0  \ Y  LLI  in ^  =  -12-537G  +  0-9539X  N  =  3G  20»0  CL 15.01  10.0 5»0 0«0 O'O  5.0  10«0 15«0 20»0 25»0 TEMPERATURE (°C)  F i g . 17. E f f e c t o f temperature on p u l s e r a t e i n C_. b i f i d a s i g n a l s . A = male s i g n a l s ; B = female s i g n a l s . Specimens from B r i t i s h Columbia, C h i l c o t i n , Beeche's P r a i r i e , Lake Lye.  30.0  4 50»0^.  45»0  Y = -7°9G27 +  1-5535X  N  Y •=  0-7934X  N =  -0-9917 +  =  9  15  40»0  35»0_. U LLI  ^  30*01  LD  25»0  Ll LD LL  15.01  10.0..  5.O..  0«0. 0.0  5.0  10.0  15.0  20.0  25»0  30»0  TEMPERATURE ( ° C )  F i g . 18. E f f e c t o f temperature on p u l s e r a t e i n C_. k u i t e r t i male s i g n a l s . Symbols: t r i a n g l e = f i r s t p u l s e group o f t h e s i g n a l ; X.= second p u l s e group o f t h e s i g n a l . Specimens from C a l i f o r n i a , Tuolumne Co., T i o g a Pass.  50  0-0  5-0  .10-0  15-0  TEMPERATURE  EO-0  E5-0  30*0  C°C)  F i g . 1 9 . E f f e c t o f temperature on p u l s e r a t e i n C. a n d e r s o n i male s i g n a l s . Symbols as i n F i g . 1 8 . Specimens from-Washingt o n , Whatcom Co., C u s t e r .  51 5-4023  +  0-G3G5X  N  =  35  25-0  20»0  15.0  10»0  20.0  25.0  30»0  25.0  30« 0  \ 4-1915  0-0  5-0  10-0  +  1-0240X  15»0  TEMPERATURE  20«0  C°C)  F i g . 20. E f f e c t o f temperature on p u l s e r a t e i n _C. a n d e r s o n i (A) and C_. u t a h e n s i s (B) female s i g n a l s . Specimens  o f C. an-  d e r s o n i from Washington, Whatcom Co., C u s t e r and C_. u t a h e n s i s from A l b e r t a , M e d i c i n e Hat.  52  55*0 +  Y  -  -13°472G  +  2°1035X  N  =  24  Y  =  -5•9291  +  1-2253X  N  =  41  50» 0. 45.01 40*0 1 35*0 U . UJ ^ 30-01 Dl UJ LD  25»0  o-o  5.0  10-0 15-0 E0«0 E5-0 TEMPERATURE ( ° D  30.0  F i g . 2 1 . E f f e c t o f t e m p e r a t u r e on p u l s e r a t e i n C_. u t a h e n s i s male s i g n a l s . Symbols as i n F i g . 1 8 . Specimens from Washingt o n , F r a n k l i n Co., Scootenay R e s e r v o i r and Mesa..  53  Y  =  -3-7424  +  0-G849X  N  =  52  50»0  15^0  10.01  0-0  \  5»0  10.0  15.0  50»0  55»0  30»0  LD.  [jj _J  E5-0.  Y  =  -18-2553  +  1-2857X  N  = - 27  0_ 5 0 . 0 1  15.01  10.01  5-0  0.0 O'O  5-0  10.0  15.0  50»0  TEMPERATURE  55.0  30«0  (°C)  F i g . 22. E f f e c t o f temperature on p u l s e r a t e i n _C. d a k o t e n s i s s i g n a l s . A = male s i g n a l s ; B = female s i g n a l s . Specimens from A l b e r t a , Brooks.  54  E5-0-.  Y-=  -7°9740  +  0-8543X  N  -  55.0  5 o4231  15»0  +  0234GX  N  24  30.0  =  30  10«0±  5«0  0.0  o.o  5.0  10«0  15.0  TEMPERATURE  50»0  55.0  —+30.0  C°C)  F i g . 2 3 . E f f e c t ' o f temperature on p u l s e r a t e i n C_. b l a i s d e l l i s i g n a l s . A = f i r s t p u l s e group o f the male s i g n a l ; B = female s i g n a l . Specimens from B r i t i s h Columbia, Vancouver.  .55  0-0  Y  =  --0-20G8+  Y  =  2-9018  5«0  10-0  +  1-7823X  N  =•  G9  0-4458X  N  =  30  15-0  TEMPERATURE  EO-0  25«0  30-0  (°C)  F i g . 2 4 . E f f e c t o f temperature on p u l s e r a t e i n C_. w i l e y a e male s i g n a l s . Symbols: t r i a n g l e = p u l s e r a t e w i t h i n the f i r s t p u l s e group o f t h e s i g n a l ; X = p u l s e r a t e w i t h i n subsequent p u l s e groups o f t h e s i g n a l . Specimens from C a l i f o r n i a , L a s s e n Co., S a i d Lake.  56  35.0 +  Y  =  -7-3334-+  1-22G9X  N  =  41  30-01  U UJ  25-0  \  20-0  UJ Ul  15-0  _J  5  10.0 5-0  0-0 0.0  5-0  10.0  15-0  20-0  TEMPERATURE  25-0  30-0  (°C)  F i g . 25. E f f e c t o f temperature on p u l s e r a t e i n C_. w i l e y a e female s i g n a l s . Specimens from C a l i f o r n i a , L a s s e n Co., S a i d Lake.  57  4 5 "»0  Y  1°275G +  09822X  N =  Gl  Y  2°2123  0-374GX  N =  46  +  x  40-0..  x 35.0.. U LU  W  30.0  \ LD  UJ  J  E5»0..  SO.01  15.01 10.0..  5.0  0.0 0»0  5.0  10-0  15-0  20-0  TEMPERATURE  25-0  30.0  ( ° D  F i g . 2 6 . E f f e c t o f temperature on p u l s e r a t e i n £. e x p l e t a s i g n a l s . Symbols as i n F i g . 2 4 , but open c i r c l e = p u l s e r a t e w i t h i n p u l s e groups o f female s i g n a l s . Specimens from B r i t i s h Columbia, Kamloops, Lac du B o i s a r e a , LB2. R e g r e s s i o n l i n e s a r e c a l c u l a t e d f o r male s i g n a l s o n l y .  58  F i g . 27. E f f e c t of temperature on r e p e t i t o n r a t e of " u n i p u l s a t e p u l s e groups" of the second p a r t of the s i g n a l i n C_. b l a i s d e l l i male. Same specimens as i n F i g . 23'A.-  59  Y  =  -0-1704  +  0-1310X  N  =  92  5.0I  u UJ  in  4-01  \  LD CL ZD • CL CD UJ ID  3«0l  LL  1-01  0-0  0.0  5.0  10.0  15«0  20-0  TEMPERATURE  55.0  30.0  (°C)  F i g . 2 8 . E f f e c t o f t e m p e r a t u r e on r e p e t i t i o n r a t e o f p u l s e groups o f t h e second p a r t o f t h e s i g n a l i n C_. w i l e y a e male, Same specimens as i n F i g . 2 4 .  60  Y =  -0-3417  +  0-1G22X  N  59  G.04.  5.O..  u  UJ Ul  4-0..  \ LD Q_ ZJ •  3-0..  LD  UJ Ul _J ZI LL  E.O  1-0  0-0 0-0  5.0  10.0  15«0  TEMPERATURE  20-0  25.0  30-0  (°C)  F i g . 2 9 . E f f e c t of temperature on r e p e t i t i o n r a t e o f p u l s e groups of the s i g n a l s i n C_. e x p l e t a . Symbols: X = male s i g n a l s ; o = female s i g n a l s . Same specimens as i n F i g . 2 6 . R e g r e s s i o n l i n e i s c a l c u l a t e d f o r male s i g n a l s o n l y .  61 d) Sounds produced as byproduct of c l e a n i n g movements Two  types of v e r y f a i n t sounds were observed t o be  produced and c o u l d be r e c o r d e d when a specimen was  resting  on the hydrophone. These were: i ) Sounds from s i m u l t a n e o u s movements o f the h i n d l e g s over the c o s t a l margins of the f o r e wings  ( F i g . 3 0 A ) ; i i ) Sounds produced by a l t e r n a t e  movements o f the h i n d l e g s when rubbed a g a i n s t abdominal v e n t e r or e x t e r n a l g e n i t a l i a ( F i g . 3 0 B ) . These two sounds were r e c o r d e d from e v e r y s p e c i e s and both sexes, and a l l were s i m i l a r . The main f r e q u e n c y a r e a i n a l l  s p e c i e s was  around 3 - 4 k.c/sec and a l l had a p p r o x i m a t e l y the same p u l s e r a t e , about 5 p u l s e s per second f o r s i m u l t a n e o u s and 1 0 p u l s e s per second f o r a l t e r n a t e movements o f the l e g s a t 22°C. The sounds were most f r e q u e n t l y produced a f t e r a specimen was t r a n s f e r r e d from one c o n t a i n e r t o another. No annual rhythm was found i n the p r o d u c t i o n o f these sounds, and t h e y seem t o be byproducts o f c l e a n i n g movements.  M  5  3 1 l  1  S E C O N D S F i g . 30. Sound spectrograms of sounds p r o d uced as a byproduct of c l e a n i n g movements. A = C_. a n d e r s o n i f e m a l e , s i m u l t a n e o u s movements o f the h i n d l e g s on f o r e wings; B = C_. b i f i d a male, a l t e r n a t e movements of the h i n d l e g s on f o r e wings. Recorded a t 22.8 °C.  63 3. L i f e c y c l e , a n n u a l rhythm o f s t r i d u l a t i o n ,  and gonad  development G e n e r a l l y C o r i x i d a e have been r e p o r t e d t o s t r i d u l a t e d u r i n g t h e s p r i n g and e a r l y summer, o r d u r i n g t h e breeding season ( M i t i s , 1 9 3 6 ; S c h a l l e r , 1 9 5 1 ; L e s t o n ,  1 9 5 5 ; Leston  and P r i n g l e , 1 9 6 3 ; F i n k e , 1 9 6 8 ) . However, i n one case  strid-  u l a t i o n has a l s o been r e p o r t e d d u r i n g t h e f a l l ( L a r s e n , 1 9 3 8 ) . A d e t a i l e d study on l i f e  c y c l e of four species of Cenocorixa  was u n d e r t a k e n i n o r d e r t o i n v e s t i g a t e how t h e annual rhythm of s t r i d u l a t i o n  c o r r e l a t e s w i t h t h e l i f e c y c l e and s e x u a l  m a t u r i t y i n t h i s genus. a) L i f e c y c l e i ) C_. b i f i d a and C_. e x p l e t a i n i n t e r i o r B r i t i s h Columbia. The  life  c y c l e o f c e n o c o r i x i d s was s t u d i e d from s t a n -  dard sweep samples. F i g . 3 1 A shows t h e sequence o f genera t i o n s o f C_. b i f i d a i n E a s t Lake, and F i g . 3 2 A t h e same s p e c i e s i n Long Lake. I t can be seen t h a t t h e r e were two generations  i n both l o c a l i t i e s and i n Long Lake, where t h e  sampling was c o n t i n u e d  u n t i l l a t e September, t h e data show>, c  t h a t a d u l t s from t h e second g e n e r a t i o n of t h e f i r s t  as w e l l as some a d u l t s  g e n e r a t i o n d i d not reproduce, but s u r v i v e d t o  overwinter. A s i m i l a r  l i f e c y c l e p a t t e r n was observed i n  _C. b i f i d a i n a l l l a k e s except LB2. C_. e x p l e t a a l s o showed the same p a t t e r n i n Barnes Lake and Long L a k e . ( i t o n l y occurred two  i n t h e s e l a k e s and i n LB2).  The l i f e  c y c l e of the  s p e c i e s were i n phase from t h e time o f appearance o f  the f i r s t  l a r v a e i n the spring t o the f i n a l molting of larvae  i n the f a l l .  64 Fig.  33 A shows the l i f e c y c l e of C_. e x p l e t a i n the  water body LB2.  I n t h i s l a k e the s p e c i e s produced t h r e e  g e n e r a t i o n s : the f i r s t the second one was  summer g e n e r a t i o n was  very short;  l o n g e r and p a r t o f i t o v e r w i n t e r e d  p a r t of the f i r s t g e n e r a t i o n i n o t h e r l a k e s ) ; the g e n e r a t i o n s t a r t e d i n September, but was  prolonged  third  only p a r t i a l l y  s u c c e s s f u l . Owing t o the low temperatures i n l a t e the l a r v a l development was  (like  fall,  and many of the l a r v a e  f a i l e d t o r e a c h the a d u l t stage b e f o r e f r e e z e - u p : t h e y d i e d d u r i n g w i n t e r . _C. b i f i d a i n LB2 produced a s i n g l e s i m u l t a n e o u s l y w i t h the f i r s t one  generation  of G_. e x p l e t a , and a  few  l a r v a e of C_. b i f i d a were d e t e c t e d b e f o r e the second g e n e r a t i o n of C_. e x p l e t a was  completed, but a d u l t s o f C_. b i f i d a were not  found l a t e r i n the summer ( u n t i l l a t e September when a  few,  a p p a r e n t l y m i g r a t i n g specimens were c a u g h t ) . Standard  sweep samples a l s o showed t h a t the  species  were not e q u a l l y abundant i n the v a r i o u s l a k e s . E a s t Lake (Fig.  31 B) had a f a i r l y h i g h number o f _C. b i f i d a a d u l t s  i n the e a r l y s p r i n g , but d u r i n g the summer the number dec r e a s e d . The number o f i n s e c t s was larval life  of the f i r s t g e n e r a t i o n , but low f o r the second  g e n e r a t i o n : Westwick Lake (_C. End  v e r y h i g h d u r i n g the  (_C. b i f i d a ) had  b i f i d a ) and B o i t a n o Lake N o r t h  similar patterns.  In Long Lake ( F i g . 32 B) the number of _C. b i f i d a a d u l t s was  v e r y h i g h i n the e a r l y s p r i n g and a l s o a t the time  emergence of the new  of  g e n e r a t i o n s . C_. e x p l e t a a l s o produced  two g e n e r a t i o n s i n t h i s l a k e , but the number of specimens caught was v e r y low throughout the summer. I n Lake Lye  65 (C_. b i f i d a ) and  Barnes Lake (C_. b i f i d a and  l i f e c y c l e p a t t e r n was  C_. e x p l e t a )  the  s i m i l a r t o t h a t of C_. b i f i d a i n Long  Lake. ( F i g . 33  I n the water body LB2  B) t h e r e were low num-  bers of C_. e x p l e t a specimens d u r i n g the e a r l y s p r i n g the f i r s t summer g e n e r a t i o n ,  but i n the second and  g e n e r a t i o n s the p o p u l a t i o n  increased  of C_. b i f i d a specimens was  low  l a t e f a l l , and J u l y and The  and  third  markedly. The  number  both i n the e a r l y summer and  none of t h i s s p e c i e s was  observed  during  August. d i f f e r e n c e s i n the l i f e c y c l e of the s p e c i e s  the v a r i o u s l a k e s may  in  r e f l e c t d i f f e r e n c e s i n temperature  and p r o d u c t i v i t y of the l a k e s . Temperature data f o r each l a k e as w e l l as the a i r temperatures a t Westwick Lake are presented i n F i g s .  34-35-  In general,  the d a t a show few  d i f f e r e n c e s i n the l a k e t e m p e r a t u r e s , w i t h o n l y LB2 i n g on average s l i g h t l y warmer, and c o o l e r t h a n the o t h e r s . was  No  Long Lake a l i t t l e  s t u d y of the p r i m a r y p r o d u c t i v i t y  u n d e r t a k e n , but c o n d u c t i v i t y c o r r e l a t e s w i t h p r o d u c t i v i t y  (Rawson and Moore, 1 9 4 4 ) , and tal  appear-  differences i n this  parameter are o b v i o u s ( F i g .  36).  environmen-  F i g . 3 1 . Sequence o f g e n e r a t i o n s o f C_. b i f i d a i n E a s t Lake a c c o r d i n g t o s t a n d a r d sweep samples i n 1 9 6 9 . " A = per cent o f a d u l t specimens and d i f f e r e n t l a r v a l i n s t a r s . Symbols: OW = o v e r w i n t e r e d a d u l t s ; 1 = f i r s t g e n e r a t i o n a d u l t s ; 2 = second g e n e r a t i o n a d u l t s ; I t o V = d i f f e r e n t l a r v a l i n s t a r s . B = a c t u a l number o f specimens caught. Symbols: continuous l i n e = a d u l t specimens ( g e n e r a t i o n s as i n A above); d o t t e d l i n e = larvae.  66  b  CA  F i g . 32. Sequence o f g e n e r a t i o n s o f C_. b i f i d a i n Long Lake a c c o r d i n g t o s t a n d a r d sweep samples i n 1969. A = p e r cent o f a d u l t specimens and d i f f e r e n t l a r v a l B = a c t u a l number of specimens caught.  Symbols as i n F i g . 31.  instars.  &  67  b  F i g . 3 3 . Sequence o f g e n e r a t i o n s o f £. e x p l e t a i n LB2 a c c o r d i n g t o s t a n d a r d sweep samples i n 1 9 6 9 . A = p e r cent o f a d u l t specimens and d i f f e r e n t l a r v a l i n s t a r s . B = a c t u a l number o f specimens caught. ration.  Symbols as i n F i g . 3 1 , but 3 = t h i r d gene-  68  O  b  69 a  F i g . 34. D a i l y maximum and minimum t e m p e r a t u r e s a t Westwick Lake and B o i t a n o Lake d u r i n g t h e summer o 1969. A---= Westwick Lake, a i r t e m p e r a t u r e ; B = West w i c k Lake, s h a l l o w water ( 2 0 cm); C = B o i t a n o Lake s h a l l o w water ( 3 0 cm); D = B o i t a n o Lake N o r t h End, s h a l l o w water ( 1 5 cm).  70  a  3 5 - D a i l y maximum and minimum t e m p e r a t u r e s i n l a k e s i n t h e i n t e r i o r B r i t i s h Columbia d u r i n g summer o f 1 9 6 9 . A = E a s t Lake ( 2 0 cm); B = Lake ( 3 0 cm); C = Barnes Lake ( 2 5 cm); D = Long Lake ( 3 0 cm); E = LB2 ( 3 0 cm).  Fig. five the Lye  70 b'  i  1  M  J  1  1  J  1  A  S  1—  O  Fig.  3 6 . S p e c i f i c c o n d u c t i v i t y o f s u r f a c e water i n e i g h t water bodies i n the  i n t e r i o r B r i t i s h Columbia d u r i n g the summer of 1 9 6 9 . a = LB2; b = Barnes Lake c - Long Lake; d = Lake Lye; e = B o i t a n o Lake; f = Westwick Lake; g = E a s t Lake; h = B o i t a n o Lake N o r t h End.  72 i i ) C_. a n d e r s o n i and C_. b l a i s d e l l i , t h e s p e c i e s o f t h e Pacific  Westcoast.  Standard sweep samples  showed t h a t t h e r e were two  g e n e r a t i o n s o f C_. a n d e r s o n i i n t h e C u s t e r g o l f course pond d u r i n g t h e summer o f 1 9 7 0 ( F i g . 3 7 A ) . O v e r w i n t e r d a d u l t s were caught u n t i l mid A p r i l , a l t h o u g h a few s u r v i v e d i n t h e pond u n t i l mid May. The f i r s t g e n e r a t i o n a d u l t s appeared i n mid June, and t h e second g e n e r a t i o n i n e a r l y August. The f i r s t l a r v a e appeared as e a r l y as t h e b e g i n n i n g o f A p r i l , much e a r l i e r t h a n i n t h e i n t e r i o r s p e c i e s , but t h e l a r v a l development i n C_. a n d e r s o n i l a s t e d c o n s i d e r a b l y l o n g e r than i n the i n t e r i o r  species.  The number o f i n s e c t s i n t h e sweep samples the  throughout  summer was f a i r l y low ( F i g . 3 7 B ) ; t h e pond a p p a r e n t l y  has a l o w p r o d u c t i v i t y ( c o n d u c t i v i t y o f t h e s u r f a c e water from 2 6 0 micromhos/cm a t 25°C i n A p r i l t o 4 8 5 micromhos/cm at 25°C i n O c t o b e r ) . However, water from t h e pond was a l s o used f o r i r r i g a t i o n o f t h e a d j a c e n t g o l f c o u r s e lawn from June t o August, and t h e sudden decrease i n t h e water  level  may have a f f e c t e d t h e p o p u l a t i o n o f C_. a n d e r s o n i by des t r o y i n g eggs and young l a r v a e which t y p i c a l l y a r e found at t h e v e r y edge o f t h e water body. Temperature  i n c o a s t a l a r e a s i s much more even t h r o u g h -  out t h e y e a r when compared t o t h e i n t e r i o r temperatures. On the  c o a s t t h e r e was p r a c t i c a l l y no f r e e z e - u p d u r i n g t h e  w i n t e r o f 1 9 6 9 - 1 9 7 0 . However, t h e summer temperatures a r e almost t h e same as i n t h e i n t e r i o r except f o r some h o t p e r i o d s which l a s t l o n g e r i n t h e i n t e r i o r . The e a r l y and  73 m i l d s p r i n g as w e l l as t h e r e l a t i v e l y warm l a t e f a l l a p p a r e n t l y a l l o w much l o n g e r b r e e d i n g and growing p e r i o d s i n t h e c o a s t a l a r e a s . Thus, a l t h o u g h t h e g o l f course pond was l o w i n p r o d u c t i v i t y , t h e l o n g summer a l l o w e d t h e comp l e t i o n o f t h e two g e n e r a t i o n s . F o r comparison w i t h t h e i n t e r i o r temperature d a t a , F i g . 3 8 shows a i r  temperature-  d a t a from S u r r e y , S u r r e y M u n i c i p a l H a l l Weather S t a t i o n , B r i t i s h Columbia (about 2 5 k i l o m e t r e s n o r t h o f C u s t e r ) , d u r i n g t h e time when o b s e r v a t i o n s on C_. a n d e r s o n i were made. L i f e c y c l e o f C_. b l a i s d e l l i was i n i t i a l l y s t u d i e d i n a semitemporary pond i n t h e c o r n e r o f 1 6 t h Avenue and Wesbrook C r e s c e n t , Vancouver. From October 1 9 6 9 u n t i l May 1 9 7 0 the s p e c i e s was abundant i n t h e pond. The f i r s t l a r v a e were observed  on t h e same day as those o f C_. a n d e r s o n i i n Custer  ( l a t e A p r i l ) , and t h e i n i t i a l a d u l t s o f t h e f i r s t  generation  o f _C. b l a i s d e l l i appeared i n e a r l y June. However, owing t o the temporary n a t u r e o f t h e h a b i t a t , these a d u l t s l e f t t h e pond i n about two weeks as i t was d r y i n g up. I n J u l y and August t h e s p e c i e s was o c c a s i o n a l l y found i n o t h e r temporary ponds, and i n a permanent pond a t t h e M a c C l e e r y G o l f Course, Vancouver. However, t h e p o p u l a t i o n o f t h i s l a s t pond was too s c a t t e r e d t o g i v e any i n f o r m a t i o n on t h e sequence o f g e n e r a t i o n s , but i t i s assumed t h a t o n l y two g e n e r a t i o n s of C. b l a i s d e l l i were produced d u r i n g t h e summer.  M  A  M  J  J  A  S  O  F i g . 3 7 - Sequence of g e n e r a t i o n s of C_. a n d e r s o n i i n C u s t e r g o l f course pond a c c o r d i n g t o s t a n d a r d sweep samples i n 1 9 7 0 . A = per cent of a d u l t specimens and d i f f e r e n t l a r v a l B = a c t u a l number of specimens caught. F u r t h e r e x p l a n a t i o n s as i n F i g . 3 1 .  instars.  F i g . 3 8 . D a i l y maximum and minimum temperatures a t S u r r e y M u n i c i p a l H a l l Weather S t a t i o n , B r i t i s h Columbia, d u r i n g the p e r i o d o f November 1 9 6 9 - October 1 9 7 0 .  b) Gonad development Females: In the o v a r i a n development the f o l l o w i n g t h r e e s t a g e s were d i s t i n g u i s h e d : A) Undeveloped s t a g e , w i t h no r e c o g n i s a b l e oocytes (newly emerged f e m a l e s ) ; B) I n t e r m e d i a t e s t a g e , w i t h oocytes r e c o g n i s a b l e , but no c h o r i o n a t e d eggs p r e s e n t ( o v e r w i n t e r i n g f e m a l e s ) ; and C) Mature s t a g e , w i t h c h o r i o n a t e d eggs p r e s e n t . F i g . 39 shows l i g h t microscope  photo-  graphs of t h e s e stages i n C_. b i f i d a . Because s t a g e s A)  and  B) grade i n t o each other, and r e p r e s e n t immature o v a r i a n s t a g e s , t h e y were grouped t o g e t h e r i n the f i n a l  analysis.  Males: In spermatogenesis A) Zone of spermatogonia  the f o l l o w i n g s t a g e s were r e c o g n i s e d a t the t i p of the  f o l l i c l e s ; B) Zone o f r e d u c t i o n d i v i s i o n ,  testicular w i t h chromosomes  c l e a r l y v i s i b l e ; C) C y s t s of s p e r m a t i d s i n t h e i r  early  developmental  round;  s t a g e , w h i l e s p e r m a t i d s were s t i l l  D) Cysts o f spermatids i n t h e i r l a t e developmental  stage,  w h i l e s p e r m a t i d s had an o v a l shape w i t h both ends a c u t e l y produced;  E) C y s t s o f mature spermatozoa,  w h i l e the sperm  had f u l l y developed t a i l s . F i g . 40 shows l i g h t photographs  o f the s t a g e s o f spermatogenesis  F i g s . 41-43  microscope  i n C_. b i f i d a .  show the presence o f mature and immature  specimens i n E a s t Lake (C_. b i f i d a ) , Long Lake (_C. LB2  bifida),  (C_. e x p l e t a ) , and C u s t e r g o l f course pond (C_. a n d e r s o n i )  The development i n the i n t e r i o r area was  somewhat d i f f e r e n t  from t h a t i n the c o a s t a l a r e a , and so the two areas are c o n s i d e r e d s e p a r a t e l y below.  77  a  F i g - 39« L i g h t m i c r o s c o p e photographs o f s t a g e s o f o v a r i a n development i n C_. b i f i d a . A = newly emerged specimen, o v a r i a n f o l l i c l e s undeveloped; B = l a t e f a l l specimen, i n t e r m e d i a t e s t a g e w i t h o o c y t e s , but no c h o r i o n a t e d eggs p r e s e n t ; C = mature s t a g e , c h o r i o n a t e d eggs p r e s e n t ( t h i s specimen a l s o demons t r a t e s t h e s t a g e when t h e female i s r e c e p t i v e : eggs i n l a t e r a l o v i d u c t s ) . Length of the s c a l e i n d i c a t o r i s one m i l l i m e t e r d i v i d e d i n t o 0.01 mm p a r t s .  78 a  F i g . 40. L i g h t m i c r o s c o p e photographs of s t a g e s of spermatogenesis i n C, b i f i d a . A = zone of spermatog o n i a a t the t i p of the t e s t i c u l a r f o l l i c l e ; B = a c y s t i n c l u d i n g r e d u c t i o n d i v i s i o n ; C = c y s t of s p e r m a t i d s i n t h e i r e a r l y developmental s t a g e ; D = c y s t of s p e r m a t i d s i n t h e i r l a t e d e v e l o p m e n t a l s t a g e ; E = mature sperm. Length of the s c a l e i n d i c a t o r i s 0.1 mm d i v i d e d i n t o 0.01 mm p a r t s .  78 b  4  A ^^^^^^  I  d  E  — 1  Females o f t h e i n t e r i o r s p e c i e s : Samples t a k e n i n t h e s p r i n g 1 9 6 6 by Dr. G. G. E. Scudder from Long Lake showed t h a t on 1 0 A p r i l a few females  o f C_. b i f i d a had one o r two  c h o r i o n a t e d eggs w h i l e none o f C_. e x p l e t a females observed  was  t o have eggs; on 1 8 A p r i l most _C. b i f i d a  females  had 1 0 - 2 0 eggs, but C_. e x p l e t a females were s t i l l  without  eggs; 1 May both s p e c i e s had c h o r i o n a t e d eggs p r e s e n t i n the o v a r i e s . I n t h e s p r i n g o f 1 9 6 9 both s p e c i e s were f u l l y r e p r o d u c t i v e , w i t h c h o r i o n a t e d eggs when f i e l d work commenced i n e a r l y May. Overwintered  females were found t o have  eggs p r e s e n t u n t i l t h e end o f t h e g e n e r a t i o n : p a r a s i t i s e d specimens l a c k e d c h o r i o n a t e d eggs i n t h e s p r i n g . I n LB2 a l l f i r s t g e n e r a t i o n specimens o f both s p e c i e s produced eggs w i t h i n about a week of emergence, but i n a l l o t h e r l a k e s o n l y t h e i n i t i a l p a r t o f the f i r s t g e n e r a t i o n o f each s p e c i e s had f u l l y developed f i r s t g e n e r a t i o n females  ovaries; late  emerging  remained s e x u a l l y immature. The  second g e n e r a t i o n o f _C. e x p l e t a i n LB2 was observed similar  t o be  t o t h e f i r s t one i n o t h e r l a k e s , w i t h t h e i n i t i a l  part producing  eggs and t h e l a t e r females  immature. A l l females  remaining s e x u a l l y  o f t h e t h i r d g e n e r a t i o n o f C_. expleta.  i n LB2 as w e l l as t h e second g e n e r a t i o n o f b o t h C_. b i f i d a and £. e x p l e t a i n o t h e r l a k e s remained immature u n t i l t h e following spring. I n p r e v i o u s s t u d i e s i t has been suggested  that the  i n i t i a t i o n o f o v a r i a n a r r e s t i n C o r i x i d a e depends on photop e r i o d i c e f f e c t s (Young, 1 9 6 5 ; Pajunen, 1 9 7 0 ) • An experiment set up i n l a t e f a l l o f 1 9 7 0 f a i l e d t o c o n f i r m t h i s . Specimens  80 of  C. b i f i d a were brought t o the l a b o r a t o r y from Lake Lye  on 8 October and p l a c e d i n a c o n t r o l l e d environment c a b i n e t at  5°C and 6 hours p h o t o p e r i o d . 2 2 days l a t e r , c u l t u r e s w i t h  sex r a t i o o f 1 male : 2 / f e m a l e s were s e t up a t room temp e r a t u r e ( 2 1 - 2 3 ° C ) w i t h 8 hours and 1 6 hours p h o t o p e r i o d . Development o f gonads was  s t u d i e d from samples o f 1 5 females  t a k e n a t i n t e r v a l s o f f o u r days. The f i r s t female w i t h c h o r i o n a t e d eggs i n the o v a r i e s was found on the 1 2 t h day a t 1 6 hours p h o t o p e r i o d . On the 1 6 t h day two more females a t the  1 6 -hours p h o t o p e r i o d p o s s e s s e d c h o r i o n a t e d eggs i n the  o v a r i e s , but a l s o i n t h e 8 hours p h o t o p e r i o d , two females w i t h c h o r i o n a t e d eggs were found. The experiment i n d i c a t e s t h a t under t h e s e c o n d i t i o n s most o f the females d i d not a t t a i n s e x u a l m a t u r i t y w i t h i n the 1 6 day t e s t p e r i o d ; d i f f e r e n c e s between the 8 hours and 1 6 hours p h o t o p e r i o d were not d e t e c t e d . Males o f the i n t e r i o r s p e c i e s : O v e r w i n t e r e d males, p a r a s i t i s e d o r u n p a r a s i t i s e d , showed mature sperm p r e s e n t i n samples t a k e n a t the time o f i c e break-up i n 1 9 6 6 , throughout the s p r i n g 1 9 6 9 . p a r t of the f i r s t  Males b e l o n g i n g t o the  and  initial  summer g e n e r a t i o n i n a l l C a r i b o o and  C h i l c o t i n l a k e s had sperm i n the t e s t e s i m m e d i a t e l y on emergence, and sperm was  shown t o be p r e s e n t i n the f i f t h  l a r v a l i n s t a r t h a t gave r i s e t o t h e s e a d u l t s . L a t e r , the er  towards  end o f the f i r s t g e n e r a t i o n , newly emerged males o f bothb i f i d a and _C. e x p l e t a were s e x u a l l y immature, as were  all fall  specimens o f the second g e n e r a t i o n . However, i n l a t e samples some of the o l d e r specimens were observed t o  F i g . 4 l . Presence of s e x u a l l y mature specimens o f C_. b i f i d a i n E a s t Lake (A) and Long Lake (B) i n 1969. Symbols: v e r t i c a l h a t c h i n g = s e x u a l l y mature males; s t i p p l e d = s e x u a l l y mature f e m a l e s . OW = o v e r w i n t e r e d specimens; 1 = f i r s t g e n e r a t i o n ; 2 = • second g e n e r a t i o n .  %  P i g . 4 2 . P r e s e n c e - o f s e x u a l l y mature specimens o f C. e x p l e t a i n LB2 i n 1 9 6 9 . Symbols as i n F i g . 41, but 3 = t h i r d g e n e r a t i o n .  00  ro  83 have sperm i n t h e t e s t e s . I t seems p r o b a b l e t h a t these  late  f a l l i n s e c t s w i t h sperm were f i r s t g e n e r a t i o n specimens from t h e l a t t e r p a r t o f t h a t g e n e r a t i o n . In  t h e Kamloops a r e a , i n t h e water body LB2, a l l f i r s t  g e n e r a t i o n males had sperm a t t h e time o f emergence. The second g e n e r a t i o n was s i m i l a r t o t h e f i r s t one i n o t h e r lakes studied, w i t h the i n i t i a l  p a r t h a v i n g sperm on  emergence, but t h e l a t e r p a r t r e m a i n i n g immature. The t h i r d g e n e r a t i o n remained immature, b u t l a t e f a l l samples a g a i n showed some o l d specimens w i t h mature sperm i n t h e testes. Gonad development i n c o a s t a l s p e c i e s : Study o f t h e gonads i n _C. a n d e r s o n i females showed t h a t no c h o r i o n a t e d eggs were found i n o v e r w i n t e r i n g specimens i n l a t e  fall  (November) o r e a r l y s p r i n g (March). The f i r s t specimens w i t h c h o r i o n a t e d eggs appeared i n e a r l y A p r i l , and eggs were found u n t i l t h e end o f t h e o v e r w i n t e r e d g e n e r a t i o n . Females o f t h e f i r s t summer g e n e r a t i o n had eggs w i t h i n a week f r o m emergence, and a l l females (except newly emerged) caught f r o m June t o mid August had c h o r i o n a t e d eggs. The second g e n e r a t i o n a d u l t s emerging f r o m t h e b e g i n n i n g o f August u n t i l l a t e October, d i d n o t p o s s e s s c h o r i o n a t e d eggs. These females o v e r w i n t e r e d , t h e o v a r i e s d e v e l o p i n g t h e following spring. About one t h i r d o f males o f _C. a n d e r s o n i caught on 2 1 November 1 9 6 9 had mature sperm i n t h e t e s t e s , and i n March 1970  a l l t h e males examined had sperm. Males w i t h sperm  were found u n t i l t h e o v e r w i n t e r e d p o p u l a t i o n d i e d o f f .  F i g . 4 3 . Presence of s e x u a l l y mature specimens of C_. a n d e r s o n i i n C u s t e r g o l f c o u r s e pond d u r i n g the summer of 1 9 7 0 . Symbols as i n F i g . 4 l .  85 At  the b e g i n n i n g o f the f i r s t summer g e n e r a t i o n about h a l f  of t h e males had mature sperm on emergence. L a t e r , however, a l l the f i r s t g e n e r a t i o n males were found t o have mature sperm. The second g e n e r a t i o n males were w i t h o u t sperm on emergence, but samples t a k e n i n mid October showed mature sperm i n about 2 0 p e r cent o f t h e specimens, and a l s o the r e s t o f them showed c y s t s o f s p e r m a t i d s i n t h e i r  late  d e v e l o p m e n t a l stage. S c a t t e r e d o b s e r v a t i o n s on the gonad development o f C_. b l a i s d e l l i i n d i c a t e t h a t o v e r w i n t e r e d females had c h o r i o n a t e d eggs from l a t e March u n t i l the end o f t h e g e n e r a t i o n . The females o f the f i r s t g e n e r a t i o n i n the temporary pond s t u d i e d d i d not have c h o r i o n a t e d eggs i n the  o v a r i e s by the time, t h e y l e f t the pond, which seemed  t o happen w i t h i n one week from emergence. However, i n the l a b o r a t o r y t h e y were observed t o develop c h o r i o n a t e d eggs i n about a week. I n the permanent pond o f the M a c C l e e r y G o l f Course, on the o t h e r hand, females w i t h c h o r i o n a t e d eggs were found u n t i l l a t e  July.  O v e r w i n t e r i n g males o f C_. b l a i s d e l l i from a l l h a b i t a t s had  mature sperm i n the t e s t e s when o b s e r v a t i o n s were  on 1 5 October 1 9 6 9 ,  started  and sperm was p r e s e n t a l l t h r o u g h t h e  w i n t e r and i n e a r l y s p r i n g u n t i l the i n s e c t s d i e d . The  first  g e n e r a t i o n males had sperm p r e s e n t on emergence. The l a s t summer specimens w i t h mature sperm were caught on 1 9 J u l y 1970,  and i n specimens caught on 9 August no mature sperm  c o u l d be d e t e c t e d . However, on 4 October 1 9 7 0 > a f t e r a v e r y warm p e r i o d , t h e temporary pond a t 1 6 t h Avenue and  86 Wesbrook C r e s c e n t was found t o be r e p o p u l a t e d , and two t h i r d s o f t h e male specimens had mature sperm i n t h e t e s t e s .  in  The main stages o f t h e gonad c y c l e were v e r y  similar  a l l four species studied i n d e t a i l . In general,  over-  w i n t e r e d f e m a l e s d i d not p o s s e s s c h o r i o n a t e d eggs u n t i l a f t e r i c e break-up o r g e n e r a l i n c r e a s e i n t e m p e r a t u r e i n cases where no t r u e w i n t e r f r e e z e - u p  e x i s t e d . F i r s t gene-  r a t i o n f e m a l e s developed c h o r i o n a t e d eggs w i t h i n about one week o f emergence, b u t i n t h e i n t e r i o r s p e c i e s t h e l a t e r p a r t of t h i s g e n e r a t i o n remained immature u n t i l t h e f o l l o w i n g s p r i n g . A l l o f t h e second g e n e r a t i o n remained immature unt i l - t h e f o l l o w i n g s p r i n g . LB2, w i t h a p a r t i a l t h i r d generation,  was an e x c e p t i o n f r o m t h e normal p a t t e r n . I n males  the o v e r w i n t e r e d g e n e r a t i o n had mature sperm b e f o r e i c e break-up. Males o f t h e f i r s t g e n e r a t i o n had mature sperm by t h e l a s t l a r v a l i n s t a r ,  but i n t h e i n t e r i o r s p e c i e s t h e  l a t e r p a r t o f t h i s g e n e r a t i o n remained immature u n t i l l a t e fall.  I n t h e i n t e r i o r s p e c i e s t h e second g e n e r a t i o n males  remained immature d u r i n g t h e f a l l , in  but matured d u r i n g w i n t e r ;  t h e c o a s t a l s p e c i e s t h e second g e n e r a t i o n males matured  during l a t e f a l l .  I n a l l s p e c i e s t h e males r e m a i n i n g  as im-  mature showed an a r r e s t o f s p e r m a t o g e n e s i s i n the stage o f c y s t s o f spermatids (Fig.  i n t h e i r e a r l y d e v e l o p m e n t a l stage  4 4 ) . I n l a t e f a l l , when development was renewed, o l d  males developed mature sperm ( F i g . 4 5 ) , and a l s o t h e newly emerged males had s p e r m a t o g e n e s i s i n t h e stage o f c y s t s o f spermatids  i n t h e i r l a t e developmental stage,  8  F i g . 44. L i g h t m i c r o s c o p e photograph of a f o l l i c l e from an a r r e s t e d t e s t i s of C. b i f i d a . S c a l e i n d i c a t o r 1 mm, d i v i d e d i n t o 0.01 mm p a r t s .  7  88  1  Fig.  4-5.  L i g h t m i c r o s c o p e photograph of a f o l l i c l e from a  mature t e s t i s of C. b i f i d a . S c a l e as i n F i g . 44.  89 c) Annual rhythm o f s t r i d u l a t i o n i) Interior  species.  Male and female s i g n a l s of C_. b i f i d a a r e to separate  Impossible  i n f i e l d r e c o r d i n g s , but t h o s e o f C_. e x p l e t a  can be d i s t i n g u i s h e d e a s i l y . I n _C. e x p l e t a o n l y male s i g n a l s were observed i n the f i e l d . Thus, i t i s assumed t h a t i n both s p e c i e s females s t r i d u l a t e so seldom t h a t a l l s i g n a l s recorded  i n the f i e l d were produced by males.  The d i s t a n c e a t which the equipment used p i c k e d s t r i d u l a t o r y s i g n a l s was measured  up  i n Barnes Lake f o r _C.  b i f i d a t o be about 35 cm and f o r C_. e x p l e t a about 60 cm from the hydrophone.  Barnes Lake has a f a i r l y h a r d bottom  covered by o n l y a few c e n t i m e t r e s  of s o f t d e t r i t u s . I t  seems l i k e l y t h a t sounds were p i c k e d up i n h a r d bottom l a k e s (Long Lake, LB2) from l o n g e r d i s t a n c e s t h a n i n Barnes Lake, and i n s o f t bottom l a k e s (Westwick Lake, B o i t a n o Boitano  Lake,  Lake Worth End, E a s t Lake, and Lake Lye) from  s h o r t e r d i s t a n c e s t h a n i n Barnes Lake. A t low p o p u l a t i o n d e n s i t i e s f i e l d r e c o r d i n g i s not always s u c c e s s f u l (as was the case i n s t u d i e s on the c o a s t a l s p e c i e s ) . F i e l d r e c o r d i n g s made i n l a t e A p r i l 1 9 7 0 and e a r l y May 1969  showed t h a t b o t h i n t e r i o r s p e c i e s were s t r i d u l a t i n g  a t t h i s time.. S t r i d u l a t i o n o f _C. b i f i d a c o n t i n u e d  ina l l  l a k e s ( e x c l u d i n g LB2) u n t i l the end of June. I n LB2 the s i g n a l s o f C_. b i f i d a were not observed a f t e r e a r l y May, w h i c h might be owing t o the f a c t t h a t C_. e x p l e t a was  strid-  u l a t i n g i n t h i s l a k e so a c t i v e l y t h a t i t o b s c u r e d a l l o t h e r s i g n a l s . I n J u l y , C. b i f i d a s i g n a l s were no more observed  90  i n B o i t a n o Lake N o r t h End, and towards the end of J u l y u l a t i o n a l s o ceased i n E a s t Lake, Westwick  strid-  Lake, and Long  Lake, but c o n t i n u e d u n t i l the end o f the f i r s t week o f August i n Lake Lye, Barnes Lake, and B o i t a n o Lake ( F i g . 4 6 ) . C_. e x p l e t a o c c u r r e d o n l y i n Barnes Lake, Long Lake, and Stridulation  of t h i s s p e c i e s was  LB2.  observed i n Long Lake and  i n Barnes Lake u n t i l the end of J u l y , but i n LB2 s i g n a l s were r e c o r d e d as l a t e as 21 August 1 9 6 9 . ( F i g .  46).  I n September  no s i g n a l s were observed i n any l a k e , and specimens i n t o t h e l a b o r a t o r y d i d not  brought  stridulate.  On 10 October 1969 some specimens  of C_. b i f i d a from  Lake Lye and Long Lake were brought i n t o the l a b o r a t o r y ,  and  some o f the males began t o s t r i d u l a t e i m m e d i a t e l y a t room t e m p e r a t u r e . S i m i l a r s t r i d u l a t i o n was  observed i n specimens  o f C_. b i f i d a brought i n t o the l a b o r a t o r y on 1 November from ponds c l o s e t o Vernon, B r i t i s h Columbia. I t i s p r o b a b l e t h a t s t r i d u l a t i o n would a l s o o c c u r i n the f i e l d i f temper a t u r e s a l l o w . Specimens of _C. e x p l e t a brought i n t o the l a b o r a t o r y on 1 November 1969 from LB2 and a r o a d s i d e pond near F a l k l a n d , B r i t i s h Columbia, began t o s t r i d u l a t e  after  seven days a t room t e m p e r a t u r e . ii)  Coastal  species.  Study o f the s t r i d u l a t i o n of the c o a s t a l s p e c i e s  began  i n the f a l l o f 1 9 6 9 , and the o c c u r r e n c e of s t r i d u l a t i o n  was  t e s t e d b o t h i n the f i e l d and i n the l a b o r a t o r y . Only male s i g n a l s were observed d u r i n g Specimens o f b o t h C.  recordings.  a n d e r s o n i and £. b l a i s d e l l i began  t o s t r i d u l a t e i m m e d i a t e l y when brought t o the l a b o r a t o r y i n  91 mid October 1 9 6 9 , and C_. b l a i s d e l l i was a l s o observed t o s t r i d u l a t e i n t h e f i e l d a t temperatures o f 7-12°C. R e c o r d i n g s were made throughout t h e y e a r and s t r i d u l a t i o n was observed i n b o t h s p e c i e s u n t i l the. end o f J u l y . F u r t h e r , C_. b l a i s d e l l i s i g n a l s were a g a i n d e t e c t e d i n t h e b e g i n n i n g o f October, and _C. a n d e r s o n i s i g n a l s i n mid October 1 9 7 0 ( F i g . 4 6 ) . F i g . 46 shows t h a t g e n e r a l l y t h e a n n u a l rhythm o f s t r i d u l a t i o n i n C e n o c o r i x a males i n B r i t i s h Columbia i s about t h e same i n a l l s p e c i e s , i . e . they s t r i d u l a t e when t h e y a r e s e x u a l l y mature. However, a l t h o u g h m a l e s . b e g i n t o s t r i d u l a t e i n l a t e f a l l females do n o t respond t o them u n t i l t h e f o l l o w i n g s p r i n g which i s t h e time o f m a t u r a t i o n o f t h e f e m a l e s . The main d i f f e r e n c e between t h e i n t e r i o r and c o a s t a l s p e c i e s i s t h a t t h e r e l a t i v e l y h i g h temperatures on t h e c o a s t enable the  s p e c i e s t o s t r i d u l a t e much o f t h e w i n t e r , w h i l e i n t h e  i n t e r i o r , t h e l o w temperature o f t h e water i n h i b i t s u l a t i o n at t h i s time.  strid-  F i g . 46. Observed a n n u a l rhythm of s t r i d u l a t i o n and s e x u a l m a t u r i t y i n f o u r s p e c i e s of C e n o c o r i x a . £. b i f i d a : a = B o i t a n o Lake N o r t h End; b = East Lake; c = Westwick Lake; d = Long Lake; e = Barnes Lake; f = Lake Lye; g = B o i t a n o Lake. C_. e x p l e t a : h = Long Lake; i = Barnes Lake; j = LB2. C_. a n d e r s o n i : k - C u s t e r , g o l f c o u r s e pond. _C. b l a i s d e l l i : 1 = Vancouver, 16th Avenue and Wesbrook C r e s c e n t pond and M a c C l e e r y G o l f Course pond. Symbols: c o n t i n u o u s l i n e = s t r i d u l a t i o n observed; arrows = s e x u a l l y mature specimens p r e s e n t i n samples between the time i n d i c a t e d by t h e arrows: males above, females below the l i n e ; * - b e g i n n i n g of o b s e r v a t i o n s ; t = end o f o b s e r v a t i o n s .  0  ti  *T  1  [1  r  tli *  tit *  tli tli * *  tli *  tli tli * *  tli  tli  tli  93 d) M i s c e l l a n e o u s o b s e r v a t i o n s on o t h e r s p e c i e s and l o c a l i t i e s D u r i n g t h e course o f t h e f i e l d work:, s e v e r a l l o c a l i t i e s were v i s i t e d o c c a s i o n a l l y i n order t o o b t a i n o t h e r s p e c i e s o f the genus. A t t h e same time a d d i t i o n a l comparative  d a t a were  o b t a i n e d on l i f e c y c l e s . I n f o r m a t i o n was as f o l l o w s : C. b i f i d a : T h i s s p e c i e s was found s t r i d u l a t i n g and mating  i n s o u t h e r n A l b e r t a on 2 1 - 2 2 May 1 9 7 0 , but no l a r v a e  were d e t e c t e d . On 6 August most o f t h e males were n o n - s t r i d u l a t i n g , but a few s t r i d u l a t i n g ones were a l s o observed  and  many l a r v a e were c o l l e c t e d a t t h e same l o c a l i t y . On 8 J u l y the s p e c i e s was found i n n o r t h e r n Utah a t 2400 m a l t i t u d e ; c o p u l a t i n g p a i r s and s t r i d u l a t i o n were observed,  and a few  IV and V i n s t a r l a r v a e were caught a l s o . I t seems p r o b a b l e t h a t t h e l i f e c y c l e both i n s o u t h e r n A l b e r t a and n o r t h e r n Utah i s s i m i l a r t o t h a t i n i n t e r i o r B r i t i s h Columbia, w i t h two g e n e r a t i o n s p e r y e a r . C_. k u i t e r t i : The s p e c i e s was found mating  s t r i d u l a t i n g and  a t 3 0 0 0 m a l t i t u d e i n C e n t r a l C a l i f o r n i a ( T i o g a Pass)  on 5 - 6 J u l y 1 9 7 0 . No l a r v a e were d e t e c t e d . I t seems obvious t h a t t h e s p e c i e s has o n l y one g e n e r a t i o n p e r summer owing t o the low temperatures  at high altitudes.  C_. u t a h e n s i s : The s p e c i e s was found i n s o u t h e r n A l b e r t a ( s y m p a t r i c a l l y w i t h C_. b i f i d a and C_. d a k o t e n s i s ) and mating  stridulating  on 2 1 - 2 2 May 1 9 7 0 . On 6 August no C_. u t a h e n s i s  specimens were d e t e c t e d a t t h i s l o c a l i t y . S c a t t e r e d p o p u l a t i o n s of the s p e c i e s were found i n s o u t h e r n and n o r t h e r n Utah on 7 - 8 J u l y 1 9 7 0 : a d u l t males were s t r i d u l a t i n g , females had c h o r i o n a t e d eggs i n o v a r i e s , and a l s o l a r v a e were c o l l e c t e d .  94  I n s o u t h e r n Washington both on 1 0 J u l y and 1 August one  s t r i d u l a t i n g male specimen was  1970,  caught. I t seems p r o -  bable t h a t the s p e c i e s has a t l e a s t two, maybe t h r e e gener a t i o n s per year i n Utah, but i t i s not known whether the s p e c i e s breeds s u c c e s s f u l l y i n A l b e r t a or Washington. C_. d a k o t e n s i s : The A l b e r t a on 2 1 - 2 2  May  s p e c i e s was  1970,  found i n s o u t h e r n  s y m p a t r i c a l l y w i t h C_.  bifida  and _C. u t a h e n s i s . A d u l t males s t r i d u l a t e d when brought i n t o the l a b o r a t o r y and females had  c h o r i o n a t e d eggs i n the ova-  r i e s . No l a r v a e were d e t e c t e d i n the f i e l d . s p e c i e s was  On 6 August the  not found i n the same l o c a l i t i e s .  C_. b l a i s d e l l i : On 1 8 - 2 0  January 1 9 7 0 ,  the s p e c i e s  found o v e r w i n t e r i n g i n C a l i f o r n i a (San F r a n c i s c o a r e a Clam Beach); o n l y a d u l t specimens were observed.  was and  Males were  s t r i d u l a t i n g , and females d i d not have c h o r i o n a t e d eggs i n the o v a r i e s . The number of g e n e r a t i o n s a t these  localities  I s not known. C_. w i l e y a e : I n lower a l t i t u d e s (up t o 2 0 0 0 m) s p e c i e s was  the  found i n e a r l y J u l y i n C a l i f o r n i a , Oregon, Nevada,  and Utah as s t r i d u l a t i n g a d u l t s and v a r i o u s l a r v a l  instars.  On 1 August some s t r i d u l a t i n g a d u l t s were caught i n s o u t h e r n Washington. However, i n e a r l y J u l y a t h i g h a l t i t u d e s (2400 t o 3000  m)  i n C a l i f o r n i a , o n l y a d u l t s were d e t e c t e d . I t seems  p o s s i b l e t h a t the s p e c i e s has two t o t h r e e g e n e r a t i o n s  per  year a t low a l t i t u d e s , but o n l y one a t h i g h a l t i t u d e s . _C. e x p l e t a : On 29 August 1 9 6 9 still  the s p e c i e s was  found  s t r i d u l a t i n g i n c e n t r a l Washington (Soap L a k e ) ,  a l s o v a r i o u s l a r v a l i n s t a r s were caught. A s i m i l a r  and  situation  was observed  on 6 August 1970 a t t h e same l o c a l i t y .  I t seems  l i k e l y t h a t t h e s p e c i e s has t h r e e g e n e r a t i o n s p e r year i n t h i s l o c a l i t y , and the t h i r d g e n e r a t i o n i s p r o b a b l y more complete than i n LB2 i n B r i t i s h  Columbia.  96  4. D i e l p e r i o d i c i t y o f t h e s t r i d u l a t i n g  activity.  I n many s t u d i e s on European C o r i x i d a e i t has been observed t h a t t h e bugs have a d i e l p e r i o d i c i t y i n t h e i r s t r i d u l a t i n g a c t i v i t y ( c f . Jansson, 1 9 6 8 ) . I n order t o i n v e s t i g a t e t h e v a l i d i t y o f the f i e l d r e c o r d i n g s which were made u s u a l l y d u r i n g daytime i n t h e p r e s e n t was n e c e s s a r y  study, i t  t o know t h e d i e l p e r i o d i c i t y of t h e s t r i d -  u l a t i n g a c t i v i t y o f t h e v a r i o u s s p e c i e s . W i t h C_. b i f i d a t h i s was s t u d i e d ' i n ' Westwick Lake and Barnes Lake, and w i t h _C. e x p l e t a i n LB2 d u r i n g the summer of 1969 by r e c o r d i n g f i v e minutes every hour over a 24 hour p e r i o d i n s i t u . The r e s u l t s ( F i g . 47) i n d i c a t e t h a t a d i f f e r e n c e e x i s t s between t h e two s p e c i e s , a l t h o u g h the number o f s i g n a l s o b t a i n e d f o r C_. b i f i d a was n o t v e r y l a r g e , and i n _C. e x p l e t a i t was i m p o s s i b l e t o count i n d i v i d u a l s i g n a l s i f more t h a n 100 s i g n a l s were r e c o r d e d  during the f i v e  minute p e r i o d s . N e v e r t h e l e s s ,  s i g n a l s of both  s p e c i e s were r e c o r d e d  although  a t a l l times of day, C_. expleta.  seemed t o have h i g h e s t s t r i d u l a t i n g a c t i v i t y a t n i g h t t i m e , w h i l e _C. b i f i d a , w a s most a c t i v e d u r i n g t h e a f t e r n o o n . D u r i n g t h e summer o f 1970 a l a b o r a t o r y s t u d y of t h e d i e l p e r i o d i c i t y o f t h e s t r i d u l a t i n g a c t i v i t y was c a r r i e d out on a l l s p e c i e s . I n these experiments 10 male specimens were p l a c e d t o g e t h e r i n a c u l t u r e t r a y and kept under n a t u r a l l i g h t c o n d i t i o n s a t u n i f o r m room temperature over a f i v e day p e r i o d . R e c o r d i n g s were made f o r f i v e minutes each hour. The r e s u l t s o f these experiments ( F i g s . 48-51) w i t h comparisons t o f i e l d r e c o r d i n g s were as f o l l o w s :  97  _C. b i f i d a ( F i g . 4 8 A ) : D u r i n g t h e i n i t i a l two days o f the experiment t h e s p e c i e s was most a c t i v e d u r i n g t h e day, but s u b s e q u e n t l y  t h e a c t i v i t y was more g e n e r a l l y d i s t r i b u t e d  over t h e 24 hours. F o r f i e l d r e c o r d i n g s see F i g . 47 A-E. C_. k u i t e r t i ( F i g . 48 B) : I n t h e f i r s t two days c l e a r n i g h t a c t i v i t y was r e c o r d e d . The t e s t was i n t e r r u p t e d f o r t h r e e days ( i n o r d e r t o c a r r y out t h e t e s t s w i t h C_. w i l e y a e ) , and when c o n t i n u e d on t h e 6 t h t o 8 t h day, t h e s t r i d u l a t i o n o c c u r r e d b o t h i n t h e day and n i g h t . No s i g n a l s were o b t a i n e d i n f i e l d r e c o r d i n g s made d u r i n g t h e day. _C. a n d e r s o n i  (Fig. 4 9 ) :  H i g h e s t a c t i v i t y was r e c o r d e d  every day o f t h e f i v e day t e s t p e r i o d a t dusk. No s i g n a l s were observed  i n f i e l d r e c o r d i n g s made d u r i n g t h e day.  £. d a k o t e n s i s was observed  ( F i g . 50 A ) : C l e a r l y n o c t u r n a l a c t i v i t y  on t h e f i v e days t e s t e d . No s i g n a l s were o b t a i n e d  i n f i e l d r e c o r d i n g s made d u r i n g t h e day. 9.- b l a i s d e l l i a l l hours,  ( F i g . 5 1 ) : S i g n a l s were r e c o r d e d  during  but t h e h i g h e s t a c t i v i t y was a t dusk and t h e  l o w e s t around noon. S i g n a l s were a l s o observed  i n field  r e c o r d i n g s made d u r i n g t h e day and a t dusk. _C. w i l e y a e ( F i g . 48 C ) : Records show t h i s t o be a f a i r l y i n a c t i v e s p e c i e s s t r i d u l a t i n g o n l y from dawn t o noon. The t e s t was c a r r i e d out i n two p a r t s (2 + 3 d a y s ) , because C_. k u i t e r t i was t e s t e d f o r t h r e e days i n t h e mean time. I n f i e l d r e c o r d i n g s _C. w i l e y a e s i g n a l s were o b t a i n e d a t a l l hours o f t h e day. C_. e x p l e t a ( F i g . 5 0 B ) : A c c o r d i n g t o t h e l a b o r a t o r y experiment t h i s s p e c i e s i s f a i r l y i n a c t i v e ,  stridulating  m o s t l y a t n i g h t t i m e . I n t h e f i e l d s i g n a l s were o b t a i n e d a t a l l times of the day ( F i g . 47 F ) . I n C_. u t a h e n s i s o b s e r v a t i o n s were s c a t t e r e d because a t t h e most o n l y t h r e e males were a v a i l a b l e a t any one time. However, t h i s s p e c i e s seemed t o have t h e h i g h e s t a c t i v i t y a t dawn and dusk. No s i g n a l s were o b t a i n e d i n f i e l d  recordings  made d u r i n g the day. I n cases when t h e p e r i o d i c i t y i n t h e s t r i d u l a t i n g a c t i v i t y changed d u r i n g t h e t e s t p e r i o d , i t i s c o n s i d e r e d t h a t t h e f i r s t days show a p e r i o d i c i t y s i m i l a r t o t h e n a t u r a l one.  Comparison of the f i e l d r e c o r d i n g s .arid/;; the  r e c o r d i n g s i n C_. b i f i d a ( F i g s . concept.  Jansson  experimental  47 A-E and 48 A) support  this  ( 1 9 6 8 ) has shown e x p e r i m e n t a l l y i n a Euro-  pean c o r i x i d , C a l l i c o r i x a p r o d u c t a  ( R e u t . ) , t h a t the d i e l  p e r i o d i c i t y of t h e s t r i d u l a t i n g a c t i v i t y i s i n f l u e n c e d by temperature,  a l t h o u g h t h e main f a c t o r seems t o be l i g h t . Thus  the f i n a l day p e r i o d i c i t y i n t h e l a b o r a t o r y was p r o b a b l y not always n a t u r a l , owing t o t h e even room  temperature.  F i g . 4 7 . I n s i t u o b s e r v a t i o n s on d i e l p e r i o d i c i t y of the s t r i d u l a t i n g a c t i v i t y of C_. b i f i d a and C_. e x p l e t a . C_. b i f i d a : A = Westwick Lake, 1 2 - 1 3 . V . 1 9 6 9 ; B = Westwick Lake, 2 5 - 2 6 . V . 1 9 6 9 ; C = Westwick Lake, 1 6 - 1 7 . V T . 1 9 6 9 ; D = Barnes Lake, 2 7 - 2 8 . V . 1 9 6 9 ; E = Barnes Lake, 7 - 8 . V I . i 9 6 9 . C. e x p l e t a : F = LB2, 2 1 - 2 2 . V . 1 9 6 9 . O r d i n a t e ( l o w e r ) : t o t a l number of s i g n a l s d u r i n g f i v e minutes (more t h a n 1 0 0 s i g n a l s per f i v e minutes i s i m p o s s i b l e t o count i n C_. e x p l e t a ) , ( u p p e r ) : t e m p e r a t u r e . H a t c h i n g = time between sunset and s u n r i s e .  100  Fig.  48. L a b o r a t o r y experiments  stridulating  on d i e l p e r i o d i c i t y of the  a c t i v i t y of C_. b i f i d a  ( A ) , _C. k u i t e r t i ( B ) ,  and C_. w i l e y a e ( C ) . O r d i n a t e : t o t a l number of s i g n a l s p r o d uced by 10 male specimens i n a c u l t u r e t r a y d u r i n g m i n u t e s . H a t c h i n g = time between sunset and s u n r i s e d a y l i g h t t i m e ) . Dates of the e x p e r i m e n t s : A:  five (Pacific  28.IV.-3.V.1970;  B: 1 5 - 1 7 . V I I . 1 9 7 0 and 2 0 - 2 3 . V I I . 1 9 7 0 ; C: 1 7 - 1 9 . V I I . 1 9 7 0 23-26.vii.1970.  and  101  120  100  12  12  12  12  12  P i g . 4 9 . L a b o r a t o r y experiment on d i e l p e r i o d i c i t y of the s t r i d u l a t i n g a c t i v i t y of C. a n d e r s o n i . Date of the e x p e r i ment 1 5 - 2 0 . V I . 1 9 7 0 . F u r t h e r e x p l a n a t i o n s as i n F i g . 4 8 .  102  F i g . 50. L a b o r a t o r y experiments on d i e l p e r i o d i c i t y of the stridulating  a c t i v i t y of _C. d a k o t e n s i s (A) and C_. e x p l e t a ( B ) .  Dates of t h e e x p e r i m e n t s : A: 6-11.VI. 1970; B: 29.V.-3".VI. 1970. F u r t h e r e x p l a n a t i o n s as i n F i g . 48.  103  i  12  12  12  12  12  F i g . 5 1 . L a b o r a t o r y experiment ori d i e l p e r i o d i c i t y of t h e s t r i d u l a t i n g a c t i v i t y of £. b l a i s d e l l i . A = t o t a l number of the f i r s t p u l s e groups o f the s i g n a l s observed d u r i n g f i v e minute r e c o r d i n g s ; B = t o t a l number o f u n i p u l s a t e ' c l i c k s ' observed. Date of t h e experiment 2 1 - 2 6 . V I . 1 9 7 0 . F u r t h e r e x p l a n a t i o n s as i n F i g . 4 8 .  104 5.  Behavioral  r o l e of s t r i d u l a t i o n  a) Male and female response t o s t r i d u l a t o r y s i g n a l s and some other The  stimuli  t e s t s c a r r i e d out on t h e d i e l p e r i o d i c i t y o f t h e  s t r i d u l a t i n g a c t i v i t y provided  s u i t a b l e m a t e r i a l f o r ana-  l y s i n g response of males t o s i g n a l s o f other males. F i g . 52 r e p r e s e n t s each s p e c i e s  an example o f a f o u r minute r e c o r d i n g s t u d i e d . I t c a n be seen t h a t i n most  from species  t h e r e i s some tendency f o r t h e s i g n a l s t o be grouped. I t would appear thus .that t h e males respond t o s i g n a l s o f o t h e r c o n s p e c i f i c males by s t r i d u l a t i n g . I n i n i t i a l s t u d i e s i n t h e f i e l d and i n t h e l a b o r a t o r y i t was f r e q u e n t l y observed t h a t when a r e p r o d u c t i v e l y a c t i v e male came c l o s e t o a n o t h e r specimen, t h e male produced a few s i g n a l s , approached t h e other copulate.  specimen, and o f t e n t r i e d t o  On t h e other hand, sometimes c o p u l a t i o n attempts  were observed t o occur w i t h o u t any i n t r o d u c t o r y s i g n a l s . I f the specimen b e i n g approached was a female, t h e l a t t e r turned  often  away and moved o f f when t h e male was s t r i d u l a t i n g , o r  i f c o p u l a t i o n was attempted by c l a s p i n g t h e female, t h e attempt f a i l e d owing t o a r e l e a s e b e h a v i o r o f t h e female. However, d u r i n g t h e p e r i o d o f A p r i l - J u l y , c o p u l a t i n g p a i r s were f r e q u e n t l y observed i n t h e f i e l d ,  but i n i t i a t i o n o f a  s u c c e s s f u l c o p u l a t i o n was n o t observed. I f t h e specimen being approached was a n o t h e r male, t h e l a t t e r answered t h e s i g n a l s of t h e f i r s t male and both s t r i d u l a t e d i n t u r n , u n t i l one o f them nudged t h e o t h e r one away. A l t e r n a t i v e l y , t h e male approached s i m p l y came and nudged  F i g . 5 2 . R e p e t i t i o n r a t e of s i g n a l s produced by 10 male specimens i n a sample f o u r minute t e s t p e r i o d , a = _C. b i f i d a ; b = C.. k u i t e r t i ; c = C_. a n d e r s o n i ; d = C_. d a k o t e n s i s ; e = C. b l a i s d e l l i ; f = _C. w i l e y a e ; g = C_. e x p l e t a . Symbols: each bar r e p r e s e n t s one s i g n a l . Length of bar g i v e s i n d i c a t i o n of s i g n a l l e n g t h I n C_. b l a i s d e l l i each t h i n l i n e r e p r e s e n t s a u n i p u l s a t e ' c l i c k ' and a bar r e p r e sents a m u l t i p u l s a t e f i r s t p a r t of a s i g n a l .  105 b E  m  E  E  e  CO  E E E E E  e  E E E E  CD  •rt  B  e8 L  106 the s t r i d u l a t i n g one  away w i t h o u t s t r i d u l a t o r y  I n these i n t e r a c t i o n s the i n s e c t t h a t was  response.  nudged would  u s u a l l y swim away, and  the i n s e c t t h a t nudged o f t e n showed  a. c h a s i n g  sometimes f o l l o w e d the other  r e a c t i o n and  specimen  f o r s e v e r a l seconds. I n t h e s e cases i t o f t e n nudged the persued specimen a g a i n i f t h i s d i d not swim v e r y f a r . The  r o l e of s t r i d u l a t i o n between males was  studied i n  more d e t a i l i n the l a b o r a t o r y w i t h C_. b i f i d a and d e l l i by p l a c i n g a. few tub and  observing  C_.  blais-  specimens i n t o the sand l i n e d  t h e i r behavior.  bath-  I n C_. b i f i d a i t was  observed t h a t when two males happened t o come c l o s e t o each o t h e r , the sequence of events r e c o r d e d i n the observations  was  r e p e a t e d . However, i t was  field  a l s o observed  t h a t an a u d i t o r y s t i m u l u s a l o n e c o u l d i n i t i a t e the approach behavior;  i n t h i s case the approach swimming was  movement ending w i t h i n c l o s e range of the specimen, and  t h e n the s i t u a t i o n was  a circling  stridulating  continued  as  described  i n the case of v i s u a l s t i m u l u s . On the other hand, i n _C. b l a i s d e l l i a u d i t o r y s t i m u l i were observed t o induce males t o s t r i d u l a t e ,  but i t was  any moving a c t i v i t i e s ;  not observed t o  only v i s u a l  the  initiate  s t i m u l i together  with  a u d i t o r y s t i m u l i i n i t i a t e d the b e h a v i o r t h a t would l e a d t o nudging away the other  specimen.  Thus i t seems l i k e l y t h a t the nudging and  chasing  b e h a v i o r between males i s a k i n d of a g o n i s t i c b e h a v i o r s e r v i n g t o space out i n d i v i d u a l s : i s often a stimulus it  stridulation  important i n t h i s context.  seemed p o s s i b l e t h a t s t r i d u l a t i o n a l s o c o u l d  apparently However, function  107  i n sex r e c o g n i t i o n , but t h e r e was l i t t l e t o i n d i c a t e t h a t i t would serve as a p r e m a t i n g s t i m u l u s . I n o r d e r t o c l a r i f y f u r t h e r d e t a i l s i n the male and female response t o male s i g n a l s c e r t a i n l a b o r a t o r y e x p e r i ments were a r r a n g e d . These were d e s i g n e d t o f o l l o w the l i n e of i n v e s t i g a t i o n s adopted by S c h a l l e r ( 1 9 5 1 ) and F i n k e ( 1 9 6 8 ) whereby a l l a c t i v i t i e s of e x p e r i m e n t a l a n i m a l s were observed and q u a n t i f i e d . The s p e c i e s used f o r these t e s t s was _C. bifida. The e x p e r i m e n t a l a n i m a l s used were as f o l l o w s : a) One male kept a l o n e d u r i n g the e n t i r e t e s t p e r i o d ( 1 1 d a y s ) . b) One male p i c k e d a t random from a p o p u l a t i o n of 20 cfd and 20 ? ? .  c') Two. females p i c k e d a t random from a p o p u l a t i o n of 30 $ ? . d) Two females p i c k e d a t random from a p o p u l a t i o n of 20 dc? and 20 ?$ . The d i f f e r e n t t e s t c o n d i t i o n s were as f o l l o w s : i ) A l o n e (one male or two females a t a t i m e ) . i i ) W i t h s t r i d u l a t o r y s t i m u l i ( 4 - 5 s t r i d u l a t i n g males i s o l a t e d i n a cage p l a c e d i n t o the t e s t c o n t a i n e r ) . i i i ) W i t h c h e m i c a l s t i m u l i : i n water p r e v i o u s l y o c c u p i e d by two females from the 30 female c u l t u r e . i v ) W i t h c h e m i c a l s t i m u l i : i n water p r e v i o u s l y o c c u p i e d by two males from the 30 male c u l t u r e . v) With v i s u a l s t i m u l i ( a n o t h e r specimen i s o l a t e d i n a t r a n s p a r e n t c o n t a i n e r , or i n t r o d u c i n g a dead p i n n e d specimen). v i ) Back a l o n e i n the o r i g i n a l  tray.  108 The experiments on c h e m i c a l s t i m u l i were c a r r i e d out i n o r d e r t o t e s t p o s s i b l e presence of a pheromone. A c l u e f o r t h i s was o b t a i n e d from an o b s e r v a t i o n on S i g a r a omani (Hung.) males t h a t showed t h a t these began t o s t r i d u l a t e v e r y a c t i v e l y when t h e y were t r a n s f e r r e d t o a t r a y where females o f t h i s s p e c i e s had been kept p r e v i o u s l y . The c o m b i n a t i o n s used i n t h e t e s t s were as f o l l o w s : Experimental animals  Test c o n d i t i o n s  a)  i ,  i i ,i i i ,  b)  i ,  i i ,  c)  (iv), iii,  11,  (v),  -  vi,  (v),  vi,  (Iv), (v), (iv), (v),  d)  C o n d i t i o n s mentioned i n b r a c k e t s were not t e s t e d r e g u l a r l y . A c t i v i t i e s s t u d i e d were c l a s s e d under s i x h e a d i n g s : 1) C l e a n i n g , 2) T u r n i n g on t h e s p o t , 3) S h o r t swimming (swimming b u r s t s t h a t l a s t e d l e s s t h a n f i v e s e c o n d s ) , 4) Long swimming ( c o n t i n u o u s swimming which l a s t e d more t h a n f i v e s e c o n d s ) , 5) S u r f a c e v i s i t s  ( f o r renewal o f a i r storage).,  and 6) S t r i d u l a t i o n . The s t r i d u l a t o r y s i g n a l s produced both t h e e x p e r i m e n t a l a n i m a l s and t h e specimens  by  used t o  p r o v i d e t h e t e s t s t i m u l i were r e c o r d e d . Experiments on v i s u a l s t i m u l i u n f o r t u n a t e l y d i d not always work p r o p e r l y because t h e e x p e r i m e n t a l  specimens  were f r e q u e n t l y g r e a t l y d i s t u r b e d by t h e p l a c i n g o f t h e t r a n s p a r e n t c o n t a i n e r i n t o t h e t r a y . However, i n a few s u c c e s s f u l t e s t s i t seemed t h a t females d i d not respond t o t h e v i s u a l s t i m u l u s o f another specimen,  but o c c a s i o n a l l y  109 males d i d i n t h a t t h e y were observed  t o t u r n towards the  specimen i n the c o n t a i n e r , produce a few s i g n a l s , and  finally  t r y t o r e a c h the i n s e c t i n s i d e the c o n t a i n e r . A l s o a p i n n e d d r y specimen was  i n t r o d u c e d t o the e x p e r i m e n t a l a n i m a l s ,  but  u n n a t u r a l movements d u r i n g t h i s i n t r o d u c t i o n seemed a g a i n t o be a d i s t u r b i n g  factor.  A t e s t f o r the presence  of male odor was  carried  out  o n l y t h r e e times f o r each type of e x p e r i m e n t a l a n i m a l s . d i f f e r e n c e was  observed  No  when compared t o the s i t u a t i o n when  no s t i m u l i were p r e s e n t . Table I I I shows the r e s u l t s of o b s e r v a t i o n s on the b e h a v i o r of the male specimens of C_. b i f i d a under c o n d i t i o n s i,  ii,  iii,  and v i above: these r e s u l t s show t h a t i n t u r n s  on the s p o t , s u r f a c e v i s i t s , and c l e a n i n g t h e r e was  no  signif-  i c a n t d i f f e r e n c e between the t e s t c o n d i t i o n s . However, the number of s h o r t swims was  s i g n i f i c a n t l y g r e a t e r when s t r i d -  u l a t o r y s t i m u l i from o t h e r males were p r e s e n t . Long swims, on the o t h e r hand, o c c u r r e d a t an e q u a l r a t e i n the case  of  the male kept a l o n e a l l the t i m e , but i n males kept w i t h females  t h e r e seems t o be a d i f f e r e n c e between the c o n d i t i o n s  where the males were a l o n e or w i t h s t r i d u l a t o r y s t i m u l i :  the  males swam more i n the l a t t e r case. S i g n i f i c a n t d i f f e r e n c e s were a l s o found i n both e x p e r i m e n t a l s e r i e s i n the number of s t r i d u l a t o r y s i g n a l s produced by the e x p e r i m e n t a l  animals:  the male kept alone a l l the time s t r i d u l a t e d m o s t l y when the female  odor was  p r e s e n t ; however, the males kept w i t h  d i d not r e a c t to the female stimuli.  females  odor, but r e a c t e d t o s t r i d u l a t o r y  T a b l e I I I . A c t i v i t i e s of C_. b i f i d a males under v a r i o u s t e s t c o n d i t i o n s . A n a l y s i s by Friedman two-way a n a l y s i s of v a r i a n c e . Test c o n d i t i o n s as a u t h o r i s e d 15 minute t e s t p e r i o d s , each t e s t repeated culture;  s i x times. E x p l a n a t i o n s :  on page 107, 0*/$ = mixed  * - v a l u e d i f f e r s s i g n i f i c a n t l y from a l l o t h e r s ; * = s i g n i f i c a n t  diff-  erence o n l y between the two v a l u e s marked by t h i s s i g n ( c o m p a r i s o n by W i l c o x o n matched-pairs ranked-sign Specimen tested  Specific activity  test). Average number of s p e c i f i c a c t i v i t y p e r e x p e r i m e n t a l p e r i o d under t e s t c o n d i t i o n s 11  cr a l o n e  111  2  iv  P r o b a b i l i t y of o b t a i n i n g the r e s u l t by chance  cleaning  0.17 2.50  O.83 0.83  • .3.50 2.17  1.83 1.50  2. 35 1. 35  P < • 7;0 P < .80  0* a l o n e 0* from 0*/?  turns  0.50 2.50  0.33  1.00 0.17  0.17 1.50  1. 15 0. 35  P < .80 P = • 95  0* a l o n e 0" from o*/$  s h o r t swims  2.83  11.33* 17.33*  2.33  2.00 5.83  12. 05 22. 50  d* a l o n e 0* from o*/$  l o n g swims  0.00 1.67*  O.50 5.17*  0.17  0.00 3.00  1. 10 9- 77  P < .80 P < .05  alone from cf/$  surfacings  1.17 1.50  0.67 3.50  2.00  0.83 2.50  2. 65 2. 65  P < .50 P < .50  alone from o"/$  stridulation  7.00 O.67  14.33 I6.83*  32.17*  5.67 2.83  11. 35 12. 75  0* from  cf cf cf cf  o*/$  6.5O  4.33  4.00 4.83 4.00  4.00  P < .01 P < . 001  P < .01 P < . 01 (— 1  H  O  I l l  The r e s u l t s of the t e s t s w i t h females are shown i n T a b l e IV ( t e s t c o n d i t i o n s i and i i ) . No s i g n i f i c a n t erences c o u l d be d e t e c t e d  diff-  between the t e s t c o n d i t i o n s i n  the amount of c l e a n i n g or the number of t u r n s on the  spot.  However, the females kept i s o l a t e d from males showed a s i g n i f i c a n t r e d u c t i o n i n the number of s h o r t and l o n g swims as w e l l as i n s u r f a c e v i s i t s when male s i g n a l s were p r e s e n t . A l s o the females kept w i t h males showed a s i g n i f i c a n t u c t i o n i n the number of l o n g swims and s t r i d u l a t o r y s t i m u l i were p r e s e n t ,  red-  s u r f a c e v i s i t s when  but no d i f f e r e n c e  was  d e t e c t e d i n the number of s h o r t swims. I n o r d e r t o check t h a t t h e r e were no d i f f e r e n c e s i n the numbers of s t r i d u l a t o r y s i g n a l s produced by i n s e c t s used t o p r o v i d e the t e s t s t i m u l i , the number of s i g n a l s produced d u r i n g each experiment were compared by a Friedman two-way a n a l y s i s of v a r i a n c e : no s i g n i f i c a n t d i f f e r e n c e was  found. A l s o the f a c t t h a t each t e s t was  second day, was  designed  repeated  every  the e n t i r e t e s t p e r i o d being thus 11 or 13 days, i n order t o f i n d out i f the b e h a v i o r  of the  bugs would change d u r i n g the time under v a r i o u s c u l t u r e s : no e v i d e n c e of any change was The  found.  f o r e g o i n g experiments demonstrated t h a t :  a) Males s t r i d u l a t e d b) There was  spontaneously.  an i n c r e a s e i n swimming and  stridulaing  activity  i n males when s t i m u l a t e d by s i g n a l s of o t h e r males. c) A male which had  been s e p a r a t e d  from o t h e r specimens f o r  ;. some time s t r i d u l a t e d a c t i v e l y when I n presence of female odor, whereas males m a i n t a i n e d  w i t h females d i d not  react  112  Table IV. A c t i v i t i e s of CJ. b i f i d a females under v a r i o u s t e s t c o n d i t i o n s . A n a l y s i s by W i l c o x o n matched-pairs rankeds i g n t e s t . T e s t c o n d i t i o n s as a u t h o r i s e d on page 1 0 7 , 1 5 minute t e s t p e r i o d s , each t e s t r e p e a t e d seven t i m e s . E x p l a n a t i o n s : 2 ? ? a l o n e - two females from 3 0 female c u l t u r e ; 2$?/V = two females from 2 0 male and 2 0 female c u l t u r e ; n.s. = no s i g n i f i c a n t d i f f e r e n c e between the test conditions. Specimens tested  Specific activity  Average nu:ruber of s p e c i f i c a c t i v i t y p er e x p e r i m e n t a l p e r i o d und er t e s t c o n d i t i o n i ii  Probability of o b t a i n i n g the r e s u l t by chance  2?? a l o n e 2??/cr  cleaning  2.29 3.^3  3.29 3.14  n. s. n. s.  2?? a l o n e 2$$/cr  turns  8.86 6.86  2.86 2.57  n.s. n.s.  2$$ a l o n e 2$?/cT  s h o r t swims  20.14 11.00  9.14 10.00  p - .01 n. s.  2?? a l o n e 2??/^  l o n g swims  6.86 10.57  1.57 3.43  P < .05 P < .05  2?? a l o n e 2??/cr  surfacings  8.43 7.43  4.86 4.86  p < .025 p < .025  t o female  odor.  d) Females responded t o male s i g n a l s by r e m a i n i n g e) Females d i d not  motionless.  stridulate.  C a t e g o r i e s a) and b) above c o u l d be e x p l a i n e d as a g o n i s t i c b e h a v i o r s p a c i n g out the males. However, c)  an and  d) i n d i c a t e t h a t s t r i d u l a t i o n might a l s o have something t o do w i t h premating spontaneously  b e h a v i o r . One  could hypothesize that a  s t r i d u l a t i n g male, a f t e r h a v i n g been a p a r t  f r o m f e m a l e s , i s induced t o c a l l a c t i v e l y by odor of a female i n the v i c i n i t y . The the female  s i g n a l s of the male would keep  s t a t i o n a r y , thus g i v i n g the male a chance t o  f i n d the mate a c c o r d i n g t o  odor.  114 b) M a t i n g i n C. b i f i d a F u r t h e r experiments were c a r r i e d out i n o r d e r t o check whether the h y p o t h e s i s on e x i s t e n c e of s t r i d u l a t i o n - o d o r i n t e r a c t i o n c o u l d be shown t o have any r o l e i n a c t u a l mating of  the bugs. A s i n g l e female _C. b i f i d a from the c u l t u r e o f 30  females  kept i s o l a t e d from males f o r 20 days, was i n t r o d u c e d i n t o the t r a y o f the male kept a l o n e f o r t h e p r e v i o u s experiments. C l o s e o b s e r v a t i o n of both i n s e c t s w i t h c o n t i n u o u s tape r e c o r d i n g was c a r r i e d out. A t f i r s t ,  both specimens  were  observed t o swim around a p p a r e n t l y a t random, but a f t e r  about  t h r e e minutes the male produced a s i g n a l , and i m m e d i a t e l y a f t e r w a r d s t h e female, r e m a i n i n g s t a t i o n a r y , responded  by  p r o d u c i n g a s t r i d u l a t o r y signal'. S t r a i g h t away the male s t a r t e d t o swim r a p i d l y i n s m a l l c i r c l e s , s t o p p i n g a t i n t e r v a l s t o s t r i d u l a t e a g a i n . The female remained m o t i o n l e s s and answered t h e male s i g n a l each t i m e , but a t no time d i d the female swim i n response. The male c o n t i n u e d s e a r c h i n g , but e v i d e n t l y was not a b l e t o o r i e n t a t e d i r e c t l y towards the female (owing t o echo i n the p l a s t i c t r a y used f o r the t e s t , see below). F i n a l l y , one and a h a l f minutes a f t e r the f i r s t male s i g n a l was r e c o r d e d , the male l o c a t e d the female and a successful copulation occurred. This copulation l a s t e d about 15 minutes. H a l f a minute a f t e r the c o p u l a t i o n was completed the male began t o s t r i d u l a t e a g a i n , but a t t h i s time t h e r e was no s t r i d u l a t o r y response from the female. Once mated, the female would not respond t o a s t r i d u l a t i n g male for  s e v e r a l days. T h i s experiment was r e p e a t e d s e v e r a l times  115  w i t h C_. b i f i d a w i t h t h e same r e s u l t . Even i f a c o p u l a t i o n was i n t e r r u p t e d 2-3 seconds a f t e r t h e g e n i t a l c o n t a c t , t h i s was enough f o r t h e female n o t t o respond any more t o t h e male s t r i d u l a t i o n by answering. The f a c t t h a t males do o r i e n t a t e a c c o r d i n g t o t h e female s i g n a l s c o u l d not be s t u d i e d i n t h e c u l t u r e t r a y s used f o r the f i r s t mating e x p e r i m e n t s , e v i d e n t l y because o f echoes from t h e w a l l s . However, i n experiments c a r r i e d out i n t h e sand l i n e d b a t h t u b i t was demonstrated t h a t t h e female s i g n a l s do s e r v e i n o r i e n t a t i o n o f t h e male: when female s i g n a l s were p l a y e d back, from tape r e c o r d i n g s t h e males congregated around t h e l o u d s p e a k e r and would remain so p o s i t i o n e d as l o n g as t h e p l a y b a c k was c o n t i n u e d , t r y i n g t o f i n d "the f e m a l e " i n t h e l o u d s p e a k e r . A l s o when a r e c e p t i v e female was p l a c e d i n t o the bathtub w i t h a s t r i d u l a t i n g male, t h e former d i d not need t o answer t h e male c a l l s more t h a n once when t h e male swam s t r a i g h t t o t h e female and c o p u l a t e d . Only females kept i s o l a t e d from males f o r a t l e a s t a week were found t o respond t o male s i g n a l s by s t r i d u l a t i n g . Females from mixed c u l t u r e s d i d n o t s t r i d u l a t e . Such nons t r i d u l a t i n g females were o f t e n t a r g e t s f o r c o p u l a t i o n a t t e m p t s , but t h e s e a t t e m p t s were never observed t o be s u c c e s s f u l . The f e m a l e s , i f c l a s p e d by males i n attempt t o c o p u l a t e , would adopt a r e l e a s e b e h a v i o r w h i c h c o n s i s t s o f v i g o r o u s swimming, coming up tb-'the water s u r f a c e , t u r n i n g a l m o s t u p s i d e down a t t h e s u r f a c e , and d i s l o d g i n g t h e male w i t h t h e h i n d l e g s . I n o t h e r cases when a s t r i d u l a t i n g male was c l o s e t o an u n r e c e p t i v e female, t h e female swam away  116  (henceforth  c a l l e d "escape" r e a c t i o n ) or towards i t , so  t h a t i t d i s t u r b e d the male ( " a g o n i s t i c " r e a c t i o n ) .  This  agonistic  b e h a v i o r i n the females was d i f f e r e n t from the  agonistic  b e h a v i o r between two males I n t h a t the females  d i d not chase the male a f t e r t h e y had nudged the male away. F i g . 5 3 shows t h e sequence o f events i n the s u c c e s s f u l m a t i n g i n C.  bifida.  117  Receptive female  Reproductively a c t i v e male  spontaneous s t r i d u l a t i o n  ^ remains s t a t i o n a r y ; stridulates  searches; orientates towards t h e female s i g n a l ; stridulates ^remains stationary; „stridulates. s e a r c h e s ; observes t h e female ( v i s u a l s t i m u l u s ) ; approaches s t a y s p a s s i v e on approach o f t h e male mounts; c o p u l a t e s  F i g . 5 3 . Diagram on t h e sequence o f events i n a m a t i n g i n C. b i f i d a .  successful  118 c) S p e c i f i c d i f f e r e n c e s i n the mating b e h a v i o r Experiments  on mating were t h e n conducted w i t h a l l  o t h e r s p e c i e s . These showed the sequence of events t o be much the same i n a l l  species.  Experiments c a r r i e d out i n the bathtub were used t o determine the d i s t a n c e a t which a r e s p o n s i v e female answered the s i g n a l s from a c o n s p e c i f i c male, and a l s o the d i s t a n c e a t which a male answered the s i g n a l s of a, female. The of t h e s e e x p e r i m e n t s , which u t i l i z e d b o t h specimens  results  stridulating  and playback: from tape r e c o r d e r t h r o u g h an under-  water l o u d s p e a k e r , are g i v e n i n T a b l e V. Some s p e c i f i c d i f f e r e n c e s between the s p e c i e s d u r i n g t h e i r mating b e h a v i o r were found and are summarised i n Table V I f o r males and i n Table V I I f o r f e m a l e s . The s t i m u l u s r e l e a s i n g the mating b e h a v i o r i n males seems t o be u s u a l l y both a u d i t o r y and v i s u a l , but i n _C. d a k o t e n s i s and C_. w i l e y a e i t seems t o be a u d i t o r y o n l y : m a l e s L b f r a i l o t h e r s p e c i e s were f r e q u e n t l y observed t o make c o p u l a t i o n attempts w i t h unr e c e p t i v e f e m a l e s . C_. w i l e y a e males c o u l d be i n d u c e d t o attempt c o p u l a t i o n w i t h u n r e c e p t i v e females by p l a c i n g both sexes i n the same c o n t a i n e r and p l a y i n g back female  signals  from a tape. I n C_. d a k o t e n s i s the o r i e n t a t i o n of males seems t o be c o m p l e t e l y dependent upon a u d i t o r y s t i m u l i because t h e y were never seen t o attempt c o p u l a t i o n w i t h a n o n - s i n g i n g female p r e s e n t i n the c o n t a i n e r , r e g a r d l e s s of p l a y b a c k s : i n all  such cases t h e y t r i e d t o f i n d the source of the female  s i g n a l . O b s e r v a t i o n s on a c t u a l mating i n t h i s s p e c i e s were u n s u c c e s s f u l owing t o the f a c t t h a t females were r e c e p t i v e  Table V. D i s t a n c e f o r r e c o g n i t i o n of s i g n a l s o f o p p o s i t e species  sex i n some Cenocorixa.  i n sand l i n e d bathtub. Each specimen was t e s t e d a g a i n s t  each d i s t a n c e  25 signals at  shown and p o s i t i v e r e a c t i o n s are shown i n p e r c e n t o f t o t a l number  of s i g n a l s t e s t e d f o r each s p e c i e s . No s i g n i f i c a n t d i f f e r e n c e s were found the i n d i v i d u a l s o f any one s p e c i e s . Species/sex tested b i f i d a o* bifida ? u t a h e n s i s o* b l a i s d e l l i cf w i l e y a e o* wileyae ? e x p l e t a o*  Number of specimens tested 2 2  3 3 3 2 2  5 100 100 100 100  between  - = distance not t e s t e d .  7.5 100  t e s t e d (cm) 10 15  20  25  30  40  50  -  -  -  -  -  -  -  -  -  -  -  -  0  0  -  0 100  0  -  100 100  0  66 100  0  —  60  100 0  85 -  -  -  -  -  100 0 100  0  0  -  -  -  -  -  -  -  -  100  100  54  0  H  T a b l e V I . S p e c i f i c d i f f e r e n c e s observed i n mating b e h a v i o r Explanations:  o f C e n o c o r i x a males.  1) = females r e c e p t i v e o n l y i n darkness; 2) = mounting s i g n a l  observed, o r i g i n unknown. Species  Number o f c o p u l a t i o n s observed successful  unsuccessful  Stimulus r e l e a s i n g mating b e h a v i o r i n males  Response t o . s i g n a l s of other males  Mounting process  bifida  6  35  visual & auditory  agonistic & answer  fast  kuiterti  0  15  visual & ?  agonistic & answer  fast ?  andersoni  5  20  auditory & visual  answer & agonistic  fast  5  auditory & visual  answer & agonistic  2-step  0  auditory  15  auditory & visual  answer  fast  utahensis dakotensis  0  blaisdelli  only  Remarks  answer ?  wileyae  6  20  auditory  none  slow  expleta  5  18  auditory (& v i s u a l ?)  none  fast  2)  H  o ro  Table V I I . S p e c i f i c d i f f e r e n c e s observed i n mating b e h a v i o r o f C e n o c o r i x a f e m a l e s . Number of c p p u l a t i o n s as i n Table V I . E x p l a n a t i o n : 1) = mounting s i g n a l o f unknown o r i g i n observed. Species  Response t o males b e f o r e c o p u l a t i o n or attempt u n r e c e p t i v e $$ r e c e p t i v e $$  Response t o males d u r i n g c o p u l a t i o n or attempt u n r e c e p t i v e $$ r e c e p t i v e ??  bifida  answer s i g n a l s , remain s t a t i o n a r y  escape, agon i s t i c or none  passive  kuiterti  answer s i g n a l s , ?  escape or none  andersoni  answer s i g n a l s , remain s t a t i o n a r y  none o r escape  utahensis  answer s i g n a l s , none remain s t a t i o n a r y , ( s e a r c h ?) answer s i g n a l s , but none o n l y i n darkness  rub male g e n i t a l i a with hind legs ?  v i g o r o u s swimming t o surface, kicking  blaisdelli  answer s i g n a l s , remain s t a t i o n a r y  escape or none  passive  p r e s s abdomen a g a i n s t 1) bottom, s u r f a c e , k i c k i n g  wileyae  answer s i g n a l s , remain s t a t i o n a r y  passive  expleta  answer s i g n a l s remain s t a t i o n a r y  none (even when male proceeds t o precopula escape or none  v i g o r o u s swimming and s u r f a c i n g when g e n i t a l contact i s t r i e d v i g o r o u s swimming, surfacing, kicking  dakotensis  passive  passive  Remarks  v i g o r o u s swimming, surfacing, kicking v i g o r o u s swimming, d i v i n g under r o c k s , kicking swimming t o s u r f a c e , kicking  1)  H  ro H  122 (= answered t o male s i g n a l s ) o n l y i n d a r k n e s s . However, i s q u i t e n a t u r a l because t h e experiments on d i e l  this  periodicity  of t h e s t r i d u l a t i n g a c t i v i t y o f males showed t h i s s p e c i e s t o be n o c t u r n a l . The importance o f t h e female s i g n a l i n a s s i s t i n g t h e male t o l o c a t e t h e female was a l s o t e s t e d by p l a c i n g s e v e r a l unreceptive  females t o g e t h e r w i t h one r e c e p t i v e female i n t h e  bathtub. I n none o f these experiments d i d t h e male attempt t o copulate with the unreceptive  females a f t e r t h e r e c e p t i v e one  s t r i d u l a t e d : i m m e d i a t e l y a f t e r t h e f i r s t answer o f t h e r e c e p t i v e female t h e male l o c a t e d t h e female and c o p u l a t i o n commenced. Thus, i n one experiment t h r e e C_. b l a i s d e l l i 2 were s e t t l e d w i t h i n 1 cm  when a male was i n t r o d u c e d .  females The male  happened t o stop c l o s e t o t h e f e m a l e s , and a f t e r a w h i l e i t produced a s i g n a l . The r e c e p t i v e female, s e t t l e d behind two unreceptive  ones, s t r i d u l a t e d i n answer t o t h e male s i g n a l .  The male i m m e d i a t e l y o r i e n t e d towards t h e group o f f e m a l e s . The s i g n a l o f t h e r e c e p t i v e female was s t i l l c o n t i n u i n g when the male passed t h e two u n r e c e p t i v e  f e m a l e s , and w i t h o u t  f u r t h e r s i g n a l s i t mounted t h e r e c e p t i v e female. Thus, i t seems obvious t h a t t h e female s i g n a l g u i d e d t h e male d i r e c t l y t o t h e female. F u r t h e r , by a r r a n g i n g an experiment w i t h r e c e p t i v e females o f C_. b i f i d a and _C. e x p l e t a t o g e t h e r ,  and i n t r o d -  u s i n g males o f e i t h e r s p e c i e s , i t .was observed t h a t i n t r a s p e c i f i c copulations  only  occurred.  When t h e r e c e p t i v e females answered t h e male c a l l and thus r e l e a s e d t h e s e a r c h i n g  behavior  i n males, t h e female  s i g n a l v e r y o f t e n s t a r t e d b e f o r e t h e male s i g n a l was comp l e t e d : t h e two s i g n a l s were p a r t l y o v e r l a p p i n g . F u r t h e r , i f the male d i d n o t produce more t h a n one s i g n a l , t h e female u s u a l l y r e p e a t e d i t s s i g n a l two t o s i x times b e f o r e c e a s i n g t o respond.  Otherwise  u l a t e spontaneously.  females were never observed  to strid-  T h i s was checked w i t h t h r e e C_. b i f i d a  and two C_. w i l e y a e females  over one 24 hour p e r i o d i n each  s p e c i e s i n a way s i m i l a r t o t h e experiments  on t h e d i e l  p e r i o d i c i t y o f t h e s t r i d u l a t i n g a c t i v i t y i n males, but no s i g n a l s were o b t a i n e d . U s u a l l y t h e female d i d n o t s e a r c h f o r t h e male, but remained s t a t i o n a r y . Only, i n one s p e c i e s , _C. u t a h e n s i s , was  one female  observed  was  i n a c u l t u r e t r a y , where t h e male had d i f f i c u l t i e s i n  l o c a t i n g t h e female  t o s e a r c h f o r t h e male, but t h i s  owing t o echoes from t h e w a l l s . I t i s  p r o b a b l e t h a t t h e females would n o t s e a r c h f o r males i n natural conditions. U n r e c e p t i v e females  showed a g o n i s t i c b e h a v i o r towards  s t r i d u l a t i n g males o n l y i n C_. b i f i d a : i n o t h e r s p e c i e s they e i t h e r swam away (escaped) or showed no s p e c i a l  behavior.  I n C_. w i l e y a e t h e u n r e c e p t i v e females remained p a s s i v e .even when t h e male mounted them, and r e l e a s e b e h a v i o r was not shown u n t i l t h e male attempted  g e n i t a l c o n t a c t . On t h e  o t h e r hand, t h i s was a s p e c i e s where t h e males most o f t e n remained i n p r e c o p u l a (mounted t h e female,  but d i d n o t t r y  g e n i t a l contact) for a while. When a male mounted a r e c e p t i v e female, t h i s happened i n most s p e c i e s by a v e r y f a s t movement and g e n i t a l  contact  124 was o b t a i n e d almost i m m e d i a t e l y .  However, i n (J. u t a h e n s i s  the p r o c e d u r e seems t o be completed i n two s t e p s : the male mounts the female f i r s t q u i t e n o r m a l l y , but r e l e a s e s the female i m m e d i a t e l y female,  and r i s e s a few m i l l i m e t r e s above the  and s e t t l e s down a g a i n . I n CJ. w i l e y a e the p r o c e d u r e  i s performed s l o w l y and c a r e f u l l y compared t o any o t h e r s p e c i e s . U s u a l l y the male s t a y s I n p r e c o p u l a f o r a few seconds: the male c l a s p s the female w i t h the f r o n t l e g s , but does not immediately  i n i t i a t e g e n i t a l contact. S i m i l a r precopulatory  b e h a v i o r was observed  i n o t h e r s p e c i e s a l s o , but o n l y between  a male and an u n r e c e p t i v e female:  i f the female d i d not  manage t o drop the male from the c l a s p i n g p o s i t i o n a f t e r the f i r s t t r i a l of g e n i t a l c o n t a c t , the p a i r o f t e n remained i n p r e c o p u l a , but as soon as the male t r i e d f u r t h e r g e n i t a l c o n t a c t s , the r e l e a s e b e h a v i o r o f the female was  initiated.  D u r i n g c o p u l a t i o n o n l y CJ. u t a h e n s i s females showed a s p e c i a l mating a c t i v i t y , by r u b b i n g the g e n i t a l r e g i o n of the males w i t h t h e i r h i n d l e g s . T h i s r u b b i n g was not to produce any sounds. Females o f a l l o t h e r s p e c i e s to  observed seemed  s t a y p a s s i v e . However, the o r i g i n of t h e mounting s i g n a l  observed  i n _C. b l a i s d e l l i and C_. e x p l e t a i s unknown, and  might be produced by the females.  The r e l e a s e b e h a v i o r o f  u n r e c e p t i v e females o f a l l s p e c i e s was observed generally  t o be  similar.  D i s s e c t i o n of r e c e p t i v e and u n r e c e p t i v e females showed t h a t the r e c e p t i v e females always had c h o r i o n a t e d eggs both i n the o v a r i e s and i n the l a t e r a l o v i d u c t s .  Unreceptive  females which had been kept i s o l a t e d from males f o r s e v e r a l  days, d i d not have any c h o r i o n a t e d eggs i n t h e l a t e r a l  ovi-  d u c t s , and a t the most had o n l y a few c h o r i o n a t e d eggs  in  the o v a r i e s : u s u a l l y the o v a r i e s were o b v i o u s l y immature.  126 d) S p e c i e s r e c o g n i t i o n A s e r i e s o f p l a y b a c k experiments was u n d e r t a k e n w h e r e i n the  response o f one s p e c i e s was t e s t e d a g a i n s t s t r i d u l a t o r y  s i g n a l s o f t h e same, and t h e n a g a i n s t s i g n a l s o f a l l o t h e r s p e c i e s . S i g n a l s o f both males and females were used and a c t i v e males and r e c e p t i v e females were u t i l i z e d i n o r d e r to the  determine t h e a b i l i t y o f the specimens  to discriminate  s i g n a l s o f t h e i r own s p e c i e s , i . e . answer t o t h e r i g h t  s i g n a l s . T a b l e s V I I I - X I summarise t h e r e s u l t s o f t h e s e experiments. A c c o r d i n g t o t a b l e V I I I males o f C_. b i f i d a , C_. k u i t e r t i , C_. a n d e r s o n i , C_. b l a i s d e l l i , and C_. w i l e y a e r e a d i l y to  answered  t h e male c a l l s o f t h e i r own s p e c i e s . C_. b i f i d a and  e s p e c i a l l y C_. w i l e y a e a l s o answered  some o t h e r s i g n a l s ,  w h i l e _C. u t a h e n s i s , _C. d a k o t e n s i s , and _C. expleta. were n o t found t o respond v e r y much t o any signal.. „ I t s h o u l d be noted t h a t males o f c e r t a i n s p e c i e s sometimes produce a complete s i g n a l o r the f i r s t p a r t o f the s i g n a l a l o n e , and thus t h e s e p o s s i b i l i t i e s were t e s t e d s e p a r a t e l y . D i f f e r e n c e s were found i n t h e response o f males and females t o t h e s e s e p a r a t e s i g n a l s . F o r i n s t a n c e C_. u t a h e n s i s and e s p e c i a l l y _C. a n d e r s o n i males responded more r e a d i l y t o t h e f i r s t p a r t o f t h e c o n s p e c i f i c male s i g n a l / w h i l e females o f t h e same s p e c i e s r e q u i r e d a complete  con-  s p e c i f i c male s i g n a l i n o r d e r t o respond ( T a b l e s V I I I and X).  On the o t h e r hand, i n £. b l a i s d e l l i and _C. w i l e y a e b o t h  males and females responded more r e a d i l y t o a complete"cons p e c i f i c male s i g n a l , and C_. k u i t e r t i males e q u a l l y w e l l  127 t o both t y p e s o f c o n s p e c i f i c male s i g n a l s . F u r t h e r , i n cases when males o f some s p e c i e s responded t o s i g n a l s o f o t h e r s p e c i e s by s t r i d u l a t i n g , i t was a l s o observed t h a t when mixed c u l t u r e s w i t h s e v e r a l s p e c i e s were a r r a n g e d , i n t e r s p e c i f i c a g o n i s t i c behavior occurred frequently. Table IX shows t h e response o f t h e males t o v a r i o u s female c a l l s . A response was o b t a i n e d e v e r y time a male was exposed t o ; t h e c a l l o f a c o n s p e c i f i c female. F u r t h e r , males o f some o f t h e s p e c i e s a l s o f r e q u e n t l y responded t o s i g n a l s from a female o f a n o t h e r s p e c i e s . However, o b s e r v a t i o n s o f the male specimens d u r i n g t h e s e i n t e r s p e c i f i c p l a y b a c k experiments showed t h a t t h e o n l y s i g n a l s i n d u c i n g s e a r c h i n g b e h a v i o r o f t h e males were s i g n a l s from a c o n s p e c i f i c female. I n experiments c a r r i e d out i n t h e sand l i n e d b a t h t u b i t was observed t h a t t h i s s e a r c h i n g b e h a v i o r i n a l l s p e c i e s always i n v o l v e d more o r l e s s d i r e c t movement t o t h e source o f t h e female s i g n a l : o n l y i f t h e meeting o f t h e sexes was p r e v e n t e d (by p l a s t i c s c r e e n o r i n p l a y b a c k e x p e r i m e n t s ) was swimming i n c i r c l e s observed. I n c o n t r a s t , t h e a g o n i s t i c b e h a v i o r o f males always i n v o l v e d a c i r c l i n g swimming movement. Table X shows t h e r e s u l t s o f experiments t e s t i n g t h e response o f females t o t h e s t r i d u l a t o r y s i g n a l s o f males. I n a l l cases t h e females responded t o s i g n a l s from a cons p e c i f i c male. I n a few cases i n v o l v i n g s p e c i e s p a i r s  occurring  a l l o p a t r i c a l l y (_C. b i f i d a - C_. a n d e r s o n i , _C. d a k o t e n s i s C_. w i l e y a e ) response t o a male s i g n a l s o f a n o t h e r s p e c i e s was r e c o r d e d . I n t h e case o f _C. b i f i d a f e m a l e s , they answered the f i r s t p a r t o f a C_. a n d e r s o n i male s i g n a l , but d i d n o t  128  respond  t o a complete s i g n a l . On t h e o t h e r hand, C_. w i l e y a e  females  responded every time t o C_. d a k o t e n s i s male s i g n a l s .  However, even i f these s p e c i e s s h o u l d occur s y m p a t r i c a l l y , the r e s u l t s do n o t n e c e s s a r i l y mean a breakdown o f t h e s t r i d u l a t o r y i s o l a t i n g mechanism, s i n c e t h e males i n v o l v e d d i d not s e a r c h f o r a mate, a l t h o u g h t h e y o c c a s i o n a l l y answered t h e wrong female  c a l l s (Table I X ) .  F i n a l l y , when female  s i g n a l s were t e s t e d a g a i n s t f e m a l e s ,  o n l y C_., e x p l e t a responded (Table X I ) . Cenocorixa  s p e c i e s occur s y m p a t r i c a l l y w i t h o t h e r  C o r i x i d a e , and where p o s s i b l e , t h e s i g n a l s o f these  other  t a x a were a l s o t e s t e d ( f o r d e s c r i p t i o n o f t h e s i g n a l s o f these o t h e r t a x a , see Appendix I I ) . The t e s t s showed t h a t some C e n o c o r i x a males answered t h e s i g n a l s from o t h e r C o r i x i d a e , b u t t h e few females which c o u l d be t e s t e d d i d not respond  ( T a b l e X I I ) . The observed  response  of Cenocorixa  males i s a p p a r e n t l y i n c o n n e c t i o n w i t h a g o n i s t i c The  behavior.  q u e s t i o n o f how c o r i x i d s d i s t i n g u i s h t h e s i g n a l s o f  c o n s p e c i f i c males o r females  from s i g n a l s o f o t h e r s p e c i e s  was n o t s t u d i e d i n d e t a i l i n t h e p r e s e n t work. However, a few o b s e r v a t i o n s were made on t h i s phenomenon. I n C_. a n d e r s o n i the female  c a l l c o n s i s t s o f one t o t h r e e s i m i l a r p u l s e groups  which a r e s e p a r a t e d from each o t h e r by s h o r t ( 1 - 2 seconds) i n t e r v a l s . When o n l y one p u l s e group was p l a y e d back t o t h e males, a s e a r c h i n g response  was observed  o n l y i n about 25  per cent o f t h e males, b u t when a sequence o f two or t h r e e p u l s e groups was p l a y e d back, a s e a r c h i n g response per c e n t o f t h e t e s t e d males was observed.  i n 100  S i m i l a r l y , C_.  129 e x p l e t a males responded t o c o n s p e c i f i c female s i g n a l s which are composed of p u l s e groups, but d i d not respond t o s i g n a l s composed of c o n t i n u o u s l y r e p e a t e d p u l s e s w h i c h had the same p u l s e r a t e as the c o n s p e c i f i c female c a l l s . I t seems p o s s i b l e t h a t the t e m p o r a l p a t t e r n of p u l s e s i s the c r i t i c a l i n species r e c o g n i t i o n i n Cenocorixa.  factor  130 Table V I I I . Response o f C e n o c o r i x a males t o playback, of male s i g n a l s . Each s p e c i e s was t e s t e d 25 times f o r each s i g n a l . Symbols: 0 = 0r20 per cent response by answering; + = 20-40 per cent response; * = 40-60 per cent response; ** = 60-80 p e r cent r e s p o n s e ; *** = 80-100 per cent response. S i n g l e u n d e r l i n i n g = s p e c i e s s y m p a t r i c ; double u n d e r l i n i n g = cons p e c i f i c s i t u a t i o n . I f two f i g u r e s appear i n the same s p e c i e s e n t r y , the upper one r e p r e s e n t s the f i r s t p a r t of the s i g n a l a l o n e used as a s t i m u l u s and the l o w e r one a complete s i g n a l used as a s t i m u l u s . Species responding  Male signal--.used as s t i m u l u s  Ti  cu -p  CQ  CU -P  <H CQ O  in  £ CU  6  CU -H -Q O M CU  3 ft S CQ  bifida  •H  CO  Ti •H  •H .Q  5 0  kuiterti  +3 fH  CU -P •H  CU Ti  -p  0 0 ***  0 0  0 0  0  + +  +  +  utahensis  5  0  dakotensis  5  0  0 + 0 0 0  blaisdelli  +  +  wileyae  + 0  CQ  CQ a cu & ti  CO  5  5  o  CQ  •H  id  andersoni  expleta  •H  -X-  CQ CQ C  •H 0 +^  o  M ti Ti  0 +  0 0 0 0 + 0 0  + 0 0 + 0  +  0 0  0 0  H H  CU  CQ •H CO  0 + 0 0 0 0 0 0 0  •**  + 0 +  •H  0  *** 0 0 0 0  cu  CO I>> 0  H •rl  0 0 0 0  + + + 0 0 0  CO  -P 0  H  ft X 0  0 0 0 0  + + *** + 0  0 0  131  Table IX. Response o f C e n o c o r i x a males t o p l a y b a c k o f female s i g n a l s . E x p l a n a t i o n s as i n Table V I I I , but - = not t e s t e d .  Species responding  Female s i g n a l used as s t i m u l u s CD -p  CO CD  o fn  -p CQ  CD  a •H  CD £2 O CD  d  •H -P  ft co  •H CH  •H  ^  o CO  -P  CD  3d  •rH  CO •H CO  co  •rH  CO  a CD  -P  o  •H H  H CD  Td co •H  CD  ti  ti  -P  0) H  H  >>  CD  a  CO -P  id  ti  H  0  +  +  0  0  0  0  0  0  ti  3  ti  X2  •H  ft  X CD  bifida  5  kuiterti  5  0  andersoni  5  0  •X--X-*  •*  +  0  **  +  utahensis  5  0  0  ***  0  0  +  0  dakotensis  5  +  0  0  ***  0  +  +  blaisdelli  5  +  wileyae  5  +  expleta  5  0  0  +  +  0  +  ***  +  132  Table X. Response o f C e n o c o r i x a females t o p l a y b a c k o f male s i g n a l s . E x p l a n a t i o n s as i n Table V I I I , but - = not t e s t e d . co  Species responding  fl  Male s i g n a l used as s t i m u l u s  0  S  •r-i O  CD  ft CO  CH  o  ••  -P  CD  Td CD  &  CO  CH  -P •rH  CD -p  JD  id  H  n -P  3 s  bifida  CO  •H •H  rH CD  d  •H  fl o  co rH  0.  co  fl  •H  CO  fl 0  0  X!  0  -P O  Td  cO  id  d  -a  fl CO  P>  •*  +  4  CO  CO  •H  +  0  •H rH H 0  0  Td CO  CO  cd •p  0  H  •rH  >i  0  H  r?H £2  •r-i  ft  0  0 0  0 0  0  0  0 0  0  0  0 0  0  CO  CO  X 0  kuiterti andersoni  3  0  utahensis  2  0  dakotensis  4  0  blaisdelli  4  0  wileyae  5  0  expleta  3  0  •X-  0 0  0 ' 0  0  0 0  0 0  0 0  0 0  0  +  0 0  0  +  0 0  0 0  0 0  0 0  0 0  +  0 0  * * **  +  0 0  +  0  +  0  0 0  133  Table X I . Response o f C e n o c o r i x a females t o playback, of female s i g n a l s . E x p l a n a t i o n s as i n Table V I I I , but - = not t e s t e d .  Species responding  Td CD -p  Female s i g n a l used as s t i m u l u s  CO  CD  •P (H  co  o fl CD  CD a -H Jd O & CD !H  d  a  ft  •H CO TJ •H CH •H  co  -p  fn CD  -P •H  d  id  fl  o co CD  • f l  fl  -P  CO  •H, H  co  r-l  CD Td  fl CD  CD  H  CD CO  >i CD  CO •H CO H  -P  CO -P  CD  cci  . ido  d  Td  id  0  0  0  o  o  0  _0_  0  0  4  0  0  andersoni  3  0  =£=  utahensis  2  _0_  0  dakotensis  4  _0_  0  blaisdelli  4  0  0  0  wileyae  5  _0_  0  +  expleta  3  0  o  bifida  CO •H  CO •H CO  CO  H •H  £  -X-  H  ft X CD  0  kuiterti 0  =  ±  =  0  o  *  0  +  0  0  +  0 o  o  0  + o  0 ***-  Table X I I . Response o f C e n o c o r i x a spp. t o p l a y b a c k o f s i g n a l s o f s y m p a t r i c s p e c i e s o f o t h e r C o r i x i d a e . Each s p e c i e s was t e s t e d 25 times f o r each s i g n a l . E x p l a n a t i o n s as i n Table V I I I , but - = not s y m p a t r i c , t h e r e f o r e n o t t e s t e d ; $ - o c c u r s i n same g e n e r a l a r e a , but was n o t found i n same water body. Cenocorixa responding  spp/sex  Number of specimens tested  S i g n a l s used f o r s t i m u l u s : Callicorixa v u l n e r a t a cf  Callicorixa audeni o*  Callicorixa t e t o n i cf  Sigara Sigara omani cf n e v a d ensiscC  Sigara nevadensis?  Corisella tarsaliscC  b i f i d a cf bifida ? k u i t e r t i cf a n d e r s o n i cf u t a h e n s i s cf d a k o t e n s i s cf dakotensis $ b l a i s d e l l i cf w i l e y a e cf wileyae ? e x p l e t a cf  5  0  *  +  0*  0*  0  2  0  0  0  0*  0*  0  0*  0*  0  10  5  0  0 0  0  3 1  0  0  2  0  0 ***  5 10 5  0  5  0  0  0  0*  0*  0 0  H  UJ  135  6. Geographic  d i s t r i b u t i o n and notes on e c o l o g y and h a b i t a t s  of t h e s p e c i e s The s p e c i e s r e c o g n i t i o n experiments ulation  indicate that s t r i d -  s e r v e s as an i s o l a t i n g mechanism between t h e s p e c i e s .  However, t h i s i s o l a t i o n may n o t always be 1 0 0 p e r cent e f f e c t i v e . Thus, i t would be n a t u r a l t o expect o t h e r i s o l a t i n g mechanisms t o e x i s t as w e l l .  I n order t o c l a r i f y these, the  g e o g r a p h i c d i s t r i b u t i o n o f t h e s p e c i e s was r e v i e w e d , and notes on e c o l o g y and h a b i t a t s were made. a) Data on d i s t r i b u t i o n and notes on e c o l o g y Data on g e n e r a l d i s t r i b u t i o n o f t h e s p e c i e s o f t h e genus C e n o c o r i x a a r e p u b l i s h e d o n l y i n Hungerford  ( 1 9 4 8 ) . Some add-  i t i o n a l i n f o r m a t i o n c a n be found i n Hungerford  (1956),  Lans-  b u r y ( 1 9 5 5 ; I 9 6 0 ) , Sparrow ( 1 9 6 6 ) , Brooks and K e l t o n ( 1 9 6 7 ) , and Scudder (1969 a ) . I n t h e f o l l o w i n g l i s t , u t i o n a l r e c o r d s a r e a c c o r d i n g t o Hungerford a u t h o r s a r e o n l y mentioned  the d i s t r i b ( 1 9 4 8 ) , and o t h e r  i f t h e i r r e c o r d s change t h e range  of t h e s p e c i e s . However, i n e v e r y case t h e p r o v i n c e s o r s t a t e s where t h e s p e c i e s were o b t a i n e d f o r t h e p r e s e n t study a r e mentioned  s e p a r a t e l y ( f o r more d e t a i l s  see Appendix  I ) . Thus  the known d i s t r i b u t i o n o f t h e s p e c i e s i s as f o l l o w s : C. b i f i d a : CANADA: B r i t i s h Columbia, A l b e r t a ,  Sas-  katchewan, Manitoba. USA: C a l i f o r n i a * , Idaho, Utah, Wyoming, Montana, N o r t h Dakota, C o l o r a d o , M i n n e s o t a , Rhode I s l a n d * * . * Lauck, D.R.j ( p e r s o n a l communication): The. specimens r e p o r t e d from C a l i f o r n i a belong e i t h e r t o C_. k u i t e r t i or C_. u t a h e n s i s . **•Rhode I s l a n d i s way out from t h e g e n e r a l d i s t r i b u t i o n a l a r e a of t h e s p e c i e s and t h e r e p o r t i s p r o b a b l y a m i s t a k e . ;  136  Scudder (1969 a) a l s o r e p o r t s Washington. F o r t h e p r e s e n t study t h e s p e c i e s was o b t a i n e d from B r i t i s h Columbia,  Alberta,  and Utah ( F i g . 5 4 ) . The  s p e c i e s seems t o occur i n f r e s h w a t e r o f m o d e r a t e l y  s a l i n e l a k e s and ponds i n t h e i n t e r i o r p l a t e a u and p r a i r i e s . A c c o r d i n g t o Scudder (1969 a) b r e e d i n g was observed i n water b o d i e s w i t h c o n d u c t i v i t y from 38.6 t o 17688 micromhos/cm a t 25°C. The l i m i t s  f o r s u c c e s s f u l b r e e d i n g d u r i n g f i e l d work  of 1969 were observed t o be between 5 0 and 13200 micromhos/ cm a t 25°C. C_. k u i t e r t i : USA: C a l i f o r n i a , (Wasatch Mountains, females  Utah. The l a t t e r r e c o r d  Duchesne), based on one male and two  (Hungerford, 1948), i s probably a m i s - i d e n t i f i c a t i o n :  the s p e c i e s i s o f t e n v e r y d i f f i c u l t t o s e p a r a t e from C_. b i f i d a ( c f . Appendix I ) . I have found 0. b i f i d a , i n t h e Wasatch Mountains  b u t n o t C_. k u i t e r t i  a r e a . D u r i n g t h e p r e s e n t study _C.  k u i t e r t i was o n l y found a t t h e type l o c a l i t y i n C a l i f o r n i a (Fig.  54)..This l o c a l i t y i s i n the high s i e r r a  at altitudes  of 3300 m, and t h e s p e c i e s i n h a b i t s s m a l l f r e s h w a t e r ponds and c r e e k s o f a s u b - a l p i n e meadow (measured c o n d u c t i v i t y o f the water 60 micromhos/cm a t 25°C). _C. a n d e r s o n i : USA: Washington, Oregon [Hungerford  (1956)  r e p o r t s t h e same S t a t e s f o r _C. m a l k i n i Hungerford, which i s a synonym o f C_. a n d e r s o n i ( c f . Appendix I ) ] . Lansbury r e p o r t e d t h e s p e c i e s from B r i t i s h Columbia,  (i960)  b o t h under i t s  c o r r e c t name and under t h e name C_. downesi Lansbury, t h e l a t t e r b e i n g a synonym o f t h e former  ( c f . Appendix I ) . I n  the p r e s e n t s t u d y t h e s p e c i e s was found i n B r i t i s h  Columbia  137  and Washington  (Fig. 5 5 ) .  The s p e c i e s o c c u r s i n f r e s h w a t e r ponds ( c o n d u c t i v i t y 4 8 5 micromhos/cm o r below a t 25°C) i n t h e l o w l a n d a r e a s between t h e . P a c i f i c c o a s t and t h e Coast Range mountains. _C. u t a h e n s i s : CANADA: B r i t i s h Columbia, A l b e r t a , Manit o b a . USA: Oregon, O'Calif o r n i a , Idaho, Nevada, Utah, A r i z o n a , New M e x i c o , C o l o r a d o , Texas, Kansas, N o r t h Dakota, South Dakota, Iowa. Brooks and K e l t o n ( 1 9 6 7 ) r e p o r t a l s o Saskatchewan. (i960)  I n a d d i t i o n t o Hungerford ( 1 9 4 8 ) ,  and Sparrow ( 1 9 6 6 )  a l s o Lansbury  r e p o r t t h e s p e c i e s from B r i t i s h  Columbia. However, i n t h e c o l l e c t i o n s • o f t h e U n i v e r s i t y o f B r i t i s h Columbia a l l t h e specimens i d e n t i f i e d as _C. u t a h e n s i s from B r i t i s h Columbia b e l o n g t o _C. b i f i d a .  I t seems  t h a t t h e r e c o r d s o f C_. u t a h e n s i s from B r i t i s h Columbia a r e based on m i s - i d e n t i f i c a t i o n s and t h e s p e c i e s does n o t o c c u r • i n t h i s p r o v i n c e . I n t h e p r e s e n t s t u d y t h e s p e c i e s was found i n A l b e r t a , Washington, and Utah ( F i g . . 5 5 ) . The species, was n o t abundant I n any o f t h e s t u d i e d a r e a s , s c a t t e r e d specimens o c c u r r i n g both i n s m a l l and l a r g e water bodies i n t h e i n t e r i o r p l a t e a u and p r a i r i e s , o f t e n i n i r r i g a t i o n r e s e r v o i r s . C o n d u c t i v i t y o f t h e water v a r i e d between 3 1 0 and I67O micromhos/cm a t 25°C. _C. d a k o t e n s i s : CANADA: North-Western  Territories,  A l b e r t a , Saskatchewan, M a n i t o b a . USA: M i n n e s o t a , I l l i n o i s , N o r t h Dakota, South Dakota. Lansbury ( 1 9 5 5 ) a l s o r e p o r t s Iowa. I n t h e p r e s e n t s t u d y t h e s p e c i e s was o b t a i n e d from Alberta (Fig. 5 6 ) . The s p e c i e s was t a k e n i n t h e s p r i n g o f 1 9 7 0 i n s h a l l o w  138  ponds w i t h c o n d u c t i v i t y of the water between IIOO-I67O micromhos/cm a t 2 5 ° C  I n August 1970 the s p e c i e s had  dis-  appeared from t h e s e ponds, and c o n d u c t i v i t y of the water from the pond where t h e s p e c i e s was most abundant  i n the  s p r i n g , had i n c r e a s e d from 1420 t o 1880 micromhos/cm a t 25°C. However, i t does not seem l i k e l y t h a t the s m a l l change i n the c o n d u c t i v i t y c o u l d have caused the d i s a p p e a r a n c e of the  s p e c i e s because t h e r e were s e v e r a l ponds w i t h l o w e r  c o n d u c t i v i t y i n the v i c i n i t y ,  but C_... d a k o t e n s i s was  not  detected. C. b l a i s d e l l i : USA: the  C a l i f o r n i a . Lansbury ( i 9 6 0 ) r e p o r t s  s p e c i e s from B r i t i s h Columbia under the name C_. colum-  b i e n s i s Lansbury. F o r the p r e s e n t s t u d y the s p e c i e s o b t a i n e d from B r i t i s h Columbia and C a l i f o r n i a  was  (Fig. 56).  The s p e c i e s seems t o f a v o r temporary or semipermanent ponds,  but i s a l s o found i n l a r g e r , more permanent water  b o d i e s and a r t i f i c i a l p a r k ponds. The l o c a t i o n of e v e r y pond where the s p e c i e s was found, was l e s s t h a n two  kilometres  from the P a c i f i c c o a s t l i n e . However, the water was  always  f r e s h ( c o n d u c t i v i t y 215 micromhos/cm or l e s s a t 25°C), a l t h o u g h a t l e a s t some o f the s t u d i e d water bodies o c c a s i o n a l l y must r e c e i v e s a l t s p r a y 'from the ocean. The  species  was not found i n ponds o f t r u l y s a l i n e environments, but Scudder  ( u n p u b l i s h e d ) has e x p e r i m e n t a l l y shown t h a t i t s u r -  vives long periods i n rather high C_. w i l e y a e : USA:  Washington,  salinities. Oregon, C a l i f o r n i a ,  Nevada,  Utah, A r i z o n a , New M e x i c o , C o l o r a d o . D u r i n g the p r e s e n t s t u d y the  s p e c i e s was  o b t a i n e d from Washington,  Oregon, C a l i f o r n i a ,  139  Nevada and Utah ( F i g . 5 7 ) . The s p e c i e s was found i n the h i g h s i e r r a up t o a l t i t udes o f 3300 m, and i n t h e i n t e r i o r p l a t e a u a t a l t i t u d e s b e g i n n i n g at.300 m.  C o n d u c t i v i t y o f the water was  between 60-300 micromhos/cm a t 25°C, but i n one  usually  location  where the s p e c i e s was v e r y abundant, a c o n d u c t i v i t y o f 85OO micromhos/cm a t 25°C was  measured.  C_, e x p l e t a : CANADA: Saskatchewan, M a n i t o b a . USA:  North  Dakota, C o l o r a d o . L a n s b u r y ( i 9 6 0 ) r e p o r t s the s p e c i e s from B r i t i s h Columbia, and Edmondson ( 1 9 6 6 ) from Washington. the p r e s e n t s t u d y the s p e c i e s was  In  o b t a i n e d from B r i t i s h  Columbia and Washington, w i t h one specimen a l s o from A l b e r t a (Fig. 57). The s p e c i e s f a v o r s h i g h e r s a l i n i t i e s t h a n any o t h e r C e n o c o r i x a s p e c i e s . Scudder ( 1 9 6 9 a) r e p o r t s b r e e d i n g i n l a k e s w i t h c o n d u c t i v i t i e s between 599O-2890O micromhos/cm a t 25°C. The d a t a c o l l e c t e d d u r i n g the summer of 1969 showed c o n d u c t i v i t i e s between 5 7 2 0 - 1 7 5 4 0 f o r the l o w e s t and h i g h e s t v a l u e s i n LB2 ( F i g . 3 6 ) , but up t o 22300 micromhos/cm a t 25°C was r e c o r d e d i n Soap Lake, Washigton; i n a l l of t h e s e l a k e s b r e e d i n g was  observed t o be s u c c e s s f u l . O c c a s i o n a l l y the  s p e c i e s was caught i n almost f r e s h w a t e r l a k e s , but t h e s e specimens were o b v i o u s l y i m m i g r a n t s because t h e y had a comp l e t e l y b l a c k mesonotum and were thus the f l y i n g form (Scudder, 1 9 6 4 ) ; no l a r v a e were observed i n t h e s e l a k e s . S y m p a t r i c s i t u a t i o n s between the s p e c i e s a r e i n d i c a t e d i n Tables V I I I - X I .  140  F i g . 54. Known g e o g r a p h i c d i s t r i b u t i o n o f C. b i f i d a ( s q u a r e s ) and _C. k u i t e r t i ( t r i a n g l e s ) . Open f i g u r e s r e f e r t o p u b l i s h e d r e c o r d s , c l o s e d ones r e p r e s e n t p l a c e s where t h e s p e c i e s were o b t a i n e d i n t h e p r e s e n t study.  141  F i g . 55. Known g e o g r a p h i c d i s t r i b u t i o n of C_. a n d e r s o n i ( s q u a r e s ) and _C. u t a h e n s i s ( t r i a n g l e s ) . Symbols as i n F i g . 54.  142  F i g . 56. Known g e o g r a p h i c d i s t r i b u t i o n of _C. d a k o t e n s i s ( s q u a r e s ) and _C. b l a i s d e l l i ( t r i a n g l e s ) . Otherwise symbols as i n F i g . ^k.  143  144 b) Notes on e c o l o g i c a l i s o l a t i o n i n s y m p a t r i c s i t u a t i o n s In cases when two o r more C e n o c o r i x a s p e c i e s were found s y m p a t r i c a l l y , c o m p a r a t i v e o b s e r v a t i o n s were made on t h e e c o l o g y and h a b i t a t s o f t h e s p e c i e s . S y m p a t r i c s i t u a t i o n s were s t u d i e d i n t h e f o l l o w i n g a r e a s : i ) B r i t i s h Columbia, P a c i f i c Westcoast: C_. a n d e r s o n i and C_. b l a i s d e l l i . These two s p e c i e s do not l i v e c o n t i n u o u s l y i n the  same ponds because  o f a p a r t i a l e c o l o g i c a l i s o l a t i o n : £.  a n d e r s o n i o c c u r s m o s t l y i n l a r g e r , c o n s t a n t water b o d i e s , w h i l e C_. b l a i s d e l l i i s m o s t l y found i n temporary r a i n w a t e r ponds and semitemporary p o o l s . A l s o , w h i l e C_. a n d e r s o n i seems t o occur on most o f t h e l o w l a n d a r e a between t h e c o a s t and the  c o a s t a l mountains, _C. b l a i s d e l l i was o n l y found w i t h i n  1-2 k i l o m e t r e s o f t h e c o a s t l i n e . B o t h s p e c i e s a r e found t o g e t h e r o n l y from l a t e f a l l u n t i l s p r i n g , i . e . d u r i n g o v e r w i n t e r i n g . They were n o t found t o breed i n t h e same ponds. i i ) B r i t i s h Columbia, i n t e r i o r p l a t e a u : C_. b i f i d a and _C. e x p l e t a . P a r t i a l e c o l o g i c a l i s o l a t i o n e x i s t s between these s p e c i e s s i n c e t h e two a r e found t o breed i n d i f f e r e n t  salinity  r a n g e s : C_. b i f i d a f a v o r s o n l y m o d e r a t e l y s a l i n e waters w i t h c o n d u c t i v i t i e s up t o 13200 micromhos/cm a t 25°C; C_. e x p l e t a o c c u r s i n s a l i n e l a k e s w i t h c o n d u c t i v i t i e s between 570022300 micromhos/cm a t 25°C (upper l i m i t i s p r o b a b l y h i g h e r ) . I n cases when t h e s p e c i e s were r e g u l a r l y found i n t h e same l a k e (Barnes Lake - c o n d u c t i v i t y 7850 i n May, 13200 i n August, and Long Lake - c o n d u c t i v i t y 98OO i n May, 1 1 6 0 0 i n August: Fig.  3 6 ) , a f u r t h e r d i f f e r e n c e was observed between t h e  s p e c i e s : C_. b i f i d a was found m o s t l y a t t h e v e r y edges o f t h e  145 water body, i n s i d e reed beds, w h i l e C_. e x p l e t a s t a y e d  mostly  i n somewhat deeper water o u t s i d e reed beds. i i i ) S o u t h e r n A l b e r t a , p r a i r i e s : C_. b i f i d a , C_. u t a h e n s i s , _C. d a k o t e n s i s , and _C. e x p l e t a . C_. expleta, does n o t u s u a l l y occur w i t h t h e o t h e r s p e c i e s s i n c e , as noted above, i t f a v o r s s a l i n e waters.  I n f r e s h w a t e r h a b i t a t s s t u d i e d , w i t h conduct-  i v i t i e s up t o 2080 micromhos/cm a t 25°C, one s i n g l e specimen of C_. e x p l e t a was found.  C_. b i f i d a was found i n more s a l i n e  waters t h a n C_. u t a h e n s i s and _C. d a k o t e n s i s , and a t conducti v i t i e s around 2000 micromhos/cm o n l y C_. b i f i d a was  found.  D e t a i l e d s t u d y o f s p e c i f i c d i f f e r e n c e s , however, remain uns o l v e d because t h e a r e a was v i s i t e d o n l y t w i c e . i v ) I n t e r i o r Washington: _C. u t a h e n s i s , C_. w i l e y a e , and C_. e x p l e t a . The t h r e e s p e c i e s were not found t o occur i n t h e same water b o d i e s , a l t h o u g h t h e y occur i n t h e same  geographic  a r e a , w i t h i n 60 km r a d i u s o f each o t h e r . E c o l o g i c a l l y C_. e x p l e t a was c l e a r l y s e p a r a t e d from t h e two o t h e r s by h i g h s a l i n i t y o f t h e h a b i t a t ( c o n d u c t i v i t y 22300 micromhos/cm a t 25°C), w h i l e the o t h e r s p e c i e s were found i n f r e s h water. C_. w i l e y a e and _C. u t a h e n s i s p o p u l a t i o n s were s c a t t e r e d and no c l e a r evidence  o f e c o l o g i c a l s e p a r a t i o n c o u l d be d e t e c t e d ,  a l t h o u g h they were found i n s e p a r a t e ponds. v ) C a l i f o r n i a , h i g h s i e r r a : C_. k u i t e r t i and C_. w i l e y a e . Both s p e c i e s were found i n f r e s h water ( c o n d u c t i v i t y 60 micromhos/cm a t 25°C), but e c o l o g i c a l l y t h e ponds i n h a b i t e d by _C. w i l e y a e seemed t o be more e u t r o p h i c t h a n t h e ones i n h a b i t e d by C_. k u i t e r t i . The l a t t e r s p e c i e s was a l s o found i n s l o w l y r u n n i n g w a t e r , w h i l e C_. w i l e y a e was o n l y o b t a i n e d from  146 stagnant ponds. v i ) Utah: <C. b i f i d a and C_. w i l e y a e ; C_. u t a h e n s i s C_. w i l e y a e .  I n Strawberry  and  R e s e r v o i r , a few specimens o f _C.  w i l e y a e were found amongst a l a r g e number o f _C. b i f i d a , and i n S t a r v a t i o n R e s e r v o i r and i n s o u t h w e s t e r n Utah, s c a t t e r e d i n d i v i d u a l s o f _C. u t a h e n s i s and C_. w i l e y a e were found  together,  No h a b i t a t , t . d i f f erences were d e t e c t e d i n the s h o r t p e r i o d o f o b s e r v a t i o n ; o n l y one v i s i t t o t h i s a r e a was p o s s i b l e .  147  IV. DISCUSSION 1. Mechanism of sound p r o d u c t i o n and a n a l y s i s of the s i g n a l s In a l l e a r l y papars on s t r i d u a l t i o n of C o r i x i d a e ( B a l l , 1846; Thomson, l8c;4; C a r p e n t e r , 1894; K i r k a l d y , 1901) main q u e s t i o n was  the mechanism of sound p r o d u c t i o n i n one  European s p e c i e s , S i g a r a s t r i a t a ( L . ) , and i t was i n c o r r e c t l y . The  the  described  s t r i d u l a t o r y s i g n a l of S_. s t r i a t a i s v e r y  c l o s e t o the s i g n a l of C_. w i l e y a e * . [ f o r sound spectrograms of the s i g n a l of S_. s t r i a t a see. F i n k e ( 1 9 6 8 ) ] , w i t h a s i m p l e m u l t i p u l s a t e f i r s t p a r t and a v e r y l o u d second p a r t composed of r e g u l a r p u l s e  groups.  M i t i s ( 1 9 3 6 ) d e s c r i b e d the mechanism of s t r i d u l a t i o n i n S_. s t r i a t a as f o l l o w s : s t r i d u l a t o r y pegs on the f r o n t femora ; are rubbed a g a i n s t sharp edges of the head:about midway between the l a b i u m and the antennae. The f i r s t p a r t of the s i g n a l i s produced by a l t e r n a t i n g , the second p a r t by s i m u l taneous movements of the f r o n t l e g s : t h i s e x p l a n a t i o n was a l s o supported  by F i n k e ( 1 9 6 8 ) . However, i n C e n o c o r i x a  the  p l e c t r u m i s the m a x i l l a r y p l a t e , l o c a t e d p o s t e r i o r t o the d o r s o l a t e r a l c o r n e r of the a n t e c l y p e u s to  (terminology according  P a r s o n s , 1965; 1 9 6 6 ) . A c c o r d i n g t o specimens i n the  collec-  t i o n s o f Dr. G. G. E. Scudder, S_. d o r s a l i s ( L e a c h . ) , which i s v e r y c l o s e l y r e l a t e d t o S_. s t r i a t a , . and which a l s o has a v e r y s i m i l a r s t r i d u l a t o r y s i g n a l ( H a s k e l l , 1 9 6 1 ) , has a m a x i l l a r y p l a t e s i m i l a r t o the p l e c t r u m of C e n o c o r i x a . T h i s a p p a r e n t l y f u n c t i o n s as the p l e c t r u m a l s o i n the genus S i g a r a (as w e l l _* I n f o r m a t i o n of S_. s t r i a t a s i g n a l s based m o s t l y on my u n p u b l i s h e d r e c o r d i n g s made i n F i n l a n d and Sweden.  own  148  as i n other s t r i d u l a t i n g European C o r i x i n a e ) . A n o t h e r d i f f e r e n c e between o b s e r v a t i o n s C o r i x i n a e and C e n o c o r i x a  on European  i s t h a t o n l y a l t e r n a t i n g movements  of t h e f r o n t l e g s were observed d u r i n g s t r i d u l a t i o n of t h e l a t t e r . According  t o spectrograms o f s i g n a l s o f S_. s t r i a t a  ( F i n k e , 1 9 6 8 ; Jansson, u n p u b l i s h e d ) i t seems u n l i k e l y t h a t _S. s t r i a t a u t i l i s e s s i m u l t a n e o u s movements o f t h e f r o n t l e g s : d e t a i l e d spectrograms do not show any d o u b l i n g Further, Finke  (1968)  o f impacts.  also claims that C a l l i c o r i x a  praeusta  ( F i e b . ) , a n o t h e r European s p e c i e s , produces t h e f i r s t  part  of i t s s i g n a l by a l t e r n a t i n g and t h e second p a r t by s i m u l taneous movements o f t h e f r o n t l e g s . The s i g n a l of t h i s species  ( F i n k e , 1 9 6 8 ; Jansson, u n p u b l i s h e d ) i s v e r y much  l i k e t h e s i g n a l s of some o t h e r C a l l i c o r i x a s p e c i e s  [_C. p r o d -  u c t a (Reut.) i n Europe, C_. audeni Hungfd. i n N o r t h  America],  and a l s o resembles v e r y much t h e s i g n a l s o f C e n o c o r i x a  an-  d e r s o n i and _C. u t a h e n s i s , and I have not observed any s i m u l taneous movements o f t h e f r o n t l e g s d u r i n g s t r i d u l a t i o n o f t h e s e s p e c i e s . I n f a c t , I have f i l m e d t h e s t r i d u l a t i o n o f C a l l i c o r i x a producta (unpublished) and  w i t h a h i g h speed camera,  the f i l m shows o n l y a l t e r n a t i n g movements o f t h e f r o n t  legs. I n the genus M i c r o n e c t a  ( M i c r o n e c t i n a e ) , t h e mechanism  of s t r i d u l a t i o n i s b e l i e v e d t o be a s s o c i a t e d w i t h t h e abdominal strigil  ( M i t i s , 1 9 3 6 ; Southwood and L e s t o n ,  1959).  Most  species:, of C o r i x i n a e a l s o have a s t r i g i l , but i t seems t o f u n c t i o n f o r attachment t o t h e female d u r i n g (Larsen, 1 9 3 8 ) .  copulation  I n two o f t h e s p e c i e s s t u d i e d i n t h e p r e s e n t  149 work., _C. b l a i s d e l l i and  C_. e x p l e t a , f a i n t s t r i d u l a t o r y  s i g n a l s were observed d u r i n g the f i r s t few  seconds of s u c c -  essful copulations.  of these sounds  was  not d e t e c t e d ,  The  mode of p r o d u c t i o n  but a p o s s i b i l i t y e x i s t s t h a t the  would have a r o l e i n p r o d u c t i o n  strigil  of these sounds: p l a c i n g  the  s t r i g i l i n t o i t s p r o p e r p o s i t i o n c o u l d produce these sounds. D e t a i l e d spectrograms on the s t r u c t u r e of the p u l s e s s t r i d u l a t o r y s i g n a l s of C o r i x i d a e have not been  in  published  p r e v i o u s l y . However, s e v e r a l s t u d i e s on O r t h o p t e r a ( e . f . H a s k e l l , 1961;  D u m o r t i e r , 1963  impact of a p u l s e  i s equivalent  b) have shown t h a t each t o one  s t r i k e of one  of the p a r s s t r i d e n s on the p l e c t r u m (when one p u l s e  tooth is  de-  f i n e d as a completed movement of the s t r i d u l a t o r y a p p a r a t u s , which i s the u s u a l d e f i n i t i o n i n b i o a c o u s t i c a l s t u d i e s ; b e i n g i n c o r r e c t I n p h y s i c a l t e r m s ) . The the p a r s s t r i d e n s i n O r t h o p t e r a and I-opterans u s u a l l y have one while  d i f f e r e n c e between  Corixidae  s i n g l e row  this  i s that Orth  of t e e t h or d e n t i c l e s  C o r i x i d a e have s e v e r a l rows of s t r i d u l a t o r y pegs. How-  ever, i t seems v e r y l i k e l y t . t h a t each impact i n the d e t a i l e d a n a l y s i s of the s i g n a l s of C e n o c o r i x a i s produced by one  peg  row. M i t i s ( 1 9 3 6 ) found a c o r r e l a t i o n between the of the s t r i d u l a t o r y pegs and d i f f e r e n t species. two  thickness  the l o u d n e s s of the s i g n a l s of  I n the p r e s e n t study, o b s e r v a t i o n s  sexes of each s p e c i e s  on  suggest t h a t the s t r u c t u r e of  the the  p l e c t r u m c o u l d a l s o a f f e c t the a m p l i t u d e of the s i g n a l s . The  s i g n a l s of C e n o c o r i x a were found t o be  species  s p e c i f i c . S i m i l a r l y , i n previous publications ( M i t i s ,  1936;  150  L e s t o n , 1955)  s i g n a l s of v a r i o u s c o r i x i d s have, been found  t o be s p e c i e s s p e c i f i c , but owing t o i n s u f f i c i e n t t e c h n i c a l a p p a r a t u s the exact d i f f e r e n c e s were not shown u n t i l i n F i n k e ' s (.1968) paper. I n t h i s paper, F i n k e sound spectrograms and  (1968)  published  o s c i l l o g r a m s of s i g n a l s of S i g a r a  s t r i a t a and C a l l i c o r i x a p r a e u s t a , and the d i f f e r e n c e s between the s p e c i e s appear t o be i n the t e m p o r a l p a t t e r n of p u l s e s and the p u l s e r e p e t i t i o n r a t e . The main f r e q u e n c y the sound i n both s p e c i e s i s a p p r o x i m a t e l y Cenocorixa  ( 3 - 5 k c / s e c ) , but F i n k e  h i g h e r overtones kc/sec  area  of  the same as i n  (1968) o b t a i n e d a l s o some  ("Oberwelle" i n German) a t 6-10  and  9-15  and over. T h i s seems t o be an a r t i f a c t , because I  a b l e t o make s i m i l a r overtones power of the s p e c t r o g r a p h The  by o v e r l o a d i n g reproduce  (Fig. 58).  d i f f i c u l t y i n analysing signals with short pulses  i s t h a t the i n d i c a t o r meter of the s p e c t r o g r a p h have time t o show the t r u e reproduce a m p l i t u d e of the v e r y s h o r t impulses i s not d e t e c t e d l e v e l ] . The  and  [ c f . .Andrieu  f a c t t h a t overtones  does not of the peaks  so a c c i d e n t a l o v e r l o a d i n g ( 1 9 6 3 ) : measuring the are a r t i f a c t s was  ated by f i l t e r i n g some s i g n a l s w i t h a sound and a n a l y s e r type 1 5 5 ^ A ( G e n e r a l Radio Co., t h a t o n l y the h i g h e r f r e q u e n c i e s a t 11-15 through,  was  sonic  demonstrvibration  Mass., U.S.A.), so kc/sec were a l l o w e d  and t h e n a n a l y s i n g the f i l t e r e d sound. The  result  showed no sounds a t these f r e q u e n c i e s , and i n t h i s experiment b o t h the i n p u t and reproduce l e v e l c o u l d be much h i g h e r w i t h normal s i g n a l , because the p o s s i b i l i t y of e f f e c t s of the lower f r e q u e n c i e s was  than  overloading  eliminated.  151  CO  M  15n  10-  5 —  ^  ••••—4—^4—-T-^•2  .4  6  S E C O N D S F i g . 5 8 . Example o f a r t i f a c t s c r e a t e d by improper a n a l y s i s of a Cenocorixa  signal:  sound spectrogram  o f one p u l s e group o f a C.. e x p l e t a male analysed  signal  by o v e r l o a d i n g reproduce power o f the  spectrograph  ( r e a d i n g s o f the VU-meter a t peaks  o f the s i g n a l  were 0, mark, l e v e l 7 ) . A l l sounds  appearing  above 6 k.c/sec are a r t i f a c t s . Note t h a t  the f i r s t t h r e e p u l s e s a r e f a i n t e r t h a n the l a s t two:  in  amplitude  t h e s t r o n g e r the sound, t h e  more a r t i f a c t s are c r e a t e d .  152  F i n k e ( 1 9 6 8 ) may  a l s o have o b t a i n e d  o v e r t o n e s because  she r e c o r d e d the s i g n a l s i n a s t y r o f o a m c o n t a i n e r . paring  s i g n a l s recorded i n a styrofoam container  I n com-  to  recordings  made under n a t u r a l c o n d i t i o n s , I found s t y r o f o a m t o change the f r e q u e n c y p a t t e r n of C e n o c o r i x a s i g n a l s . Temperature was  not u s u a l l y observed t o have an e f f e c t  on the t e m p o r a l p a t t e r n of p u l s e s  of C e n o c o r i x a s i g n a l s ,  i t c l e a r l y a f f e c t s the p u l s e r a t e and,  when a p p l i c a b l e ,  but the  p u l s e group r a t e , as w e l l as the s i g n a l l e n g t h . F i n k e ( 1 9 6 8 ) has  also published  some d a t a on temperature e f f e c t on  u l a t i o n of S i g a r a s t r i a t a ,  but t h i s was  on dur.ationf ofv.pulse  groups and p u l s e group i n t e r v a l s . Thus, a c t u a l on p u l s e  r a t e s of C o r i x i d a e  strid-  observations  other than Cenocorixa  species,  are l a c k i n g . Walker ( 1 9 6 2 ) has  s t u d i e d the e f f e c t of temperature  on s i g n a l s of s e v e r a l s p e c i e s  of c r i c k e t s . He  states  that  temperature a f f e c t s the p u l s e r a t e of c r i c k e t s i g n a l s i n a u n i f o r m way  and  the f o l l o w i n g g e n e r a l i s a t i o n s were made: i )  r a t e of change i n p u l s e r a t e w i t h temperature i s i i ) the h i g h e r greater  r a t e at a given temperature,  the  the r a t e of change; i i i ) i f r e g r e s s i o n l i n e s are  extrapolated pulses  the p u l s e  constant;  per  downward, t h e y tend t o converge a t 4°C  and  0  second.  Generally  t h e s e r u l e s a l s o seem t o f i t i n C e n o c o r i x a  s i g n a l s . F i g s . 17-26 p l o t t e d against  show t h a t a graph where p u l s e r a t e i s  temperature forms a s t r a i g h t l i n e , but  as  Walker ( 1 9 6 2 ) f u r t h e r s t a t e s f o r c r i c k e t s , i f a d e v i a t i o n from a l i n e a r r e l a t i o n s h i p i s found i t w i l l be a t the  extremes  153  o f temperature;  p u l s e r a t e s of C e n o c o r i x a  h i g h e r than expected  a t low temperatures.  seem t o be  slightly  F i g . 59 summarises  the r e g r e s s i o n l i n e s of C e n o c o r i x a males, and  t h i s shows t h a t  the r e g r e s s i o n l i n e s f o r the s p e c i e s w i t h h i g h p u l s e r a t e are g e n e r a l l y the s t e e p e s t . However, F i g . 59 a l s o shows t h a t the r e g r e s s i o n l i n e s of C e n o c o r i x a  do not converge a t 4°C and  0  p u l s e per second, but most of them (8 out o f 13) seem t o conv e r g e a t about 9°C  and  6 p u l s e s per  second.  R e g r e s s i o n l i n e s f o r female s i g n a l s were a l s o c a l c u l a t e d i n most s p e c i e s , but owing t o the s m a l l temperature range s t u d i e d the l i n e s are probably'somewhat b i a s e d . C_. w i l e y a e f e m a l e s ,  In  when more o b s e r v a t i o n s were made i n  d i f f e r e n t temperatures,  the r e g r e s s i o n l i n e i s v e r y c l o s e  t o the g e n e r a l l i n e s of the males. T h i s .would p r o b a b l y have been the case a l s o i n females o f o t h e r s p e c i e s i f more m a t e r i a l had  been a v a i l a b l e .  S i g n a l d u r a t i o n p l o t t e d a g a i n s t temperature was t o be n o n - l i n e a r i n C e n o c o r i x a  shown  ( F i g s . 2 2 - 2 4 ) . I n any  signal  i t can be shown t h a t i f the change i n the p u l s e r a t e w i t h temperature i s constant  (= l i n e a r r e g r e s s i o n ) , and the number  o f p u l s e s i n the s i g n a l i s c o n s t a n t , the d u r a t i o n of the s i g n a l does not change l i n e a r l y when the temperature changes. As an example the p u l s e r a t e of C_. b i f i d a male has  a regres-  s i o n l i n e o f Y = -O.766 + 0 . 4 6 6 X . P u l s e r a t e s a t 10°C, and 30°C on t h i s r e g r e s s i o n l i n e a r e 3.9,  8.6,  and  20°C,  13.2  p u l s e s per second, r e s p e c t i v e l y , and average number o f p u l s e s per s i g n a l was  observed  From these v a l u e s , expected  t o be 19.60  f o r the s p e c i e s .  s i g n a l d u r a t i o n s i n the above  154  10 20 3 0 T e m p e r a t u r e (°C) F i g . 59. Summary o f t h e r e g r e s s i o n l i n e s o f temperature e f f e c t on p u l s e r a t e i n C e n o c o r i x a male s i g n a l s , a = _C. w i l e y a e f a s t p u l s e r a t e ; b - C_. u t a h e n s i s f a s t p u l s e rate;, c = C_. a n d e r s o n i f a s t p u l s e r a t e ; d = (J. k u i t e r t i f a s t p u l s e r a t e ; e = _C. e x p l eta f a s t p u l s e r a t e ; f = C_. u t a h e n s i s slow p u l s e r a t e ; g = _C. a n d e r s o n i slow p u l s e r a t e ; h = (J. k u i t e r t i slow p u l s e r a t e ; i = C. b l a i s d e l l i f i r s t p a r t p u l s e r a t e ; j = _C. d a k o t e n s i s ; k = C_. e x p l e t a slow p u l s e r a t e ; 1 = CJ. w i l e y a e f i r s t p a r t p u l s e r a t e ; m = C. b i f i d a .  155  temperatures can be c a l c u l a t e d , and v a l u e s o f 5.0, 1.5  2.3,  and  seconds are o b t a i n e d . P i g . 60 A shows t h a t these  expected  v a l u e s form a curve which i s v e r y c l o s e t o the curve  obtained  from the a c t u a l o b s e r v a t i o n s on s i g n a l d u r a t i o n i n C_. b i f i d a . Thus, s i n c e the a c t u a l curve does not d e p a r t  significantly  f r o m the c a l c u l a t e d v a l u e s , i t shows t h a t the number of p u l s e s per s i g n a l (and a p p a r e n t l y the temporal p a t t e r n of p u l s e s as w e l l ) i s c o n s t a n t and independent of  temperature.  I n F i g . 60 B s i g n a l d u r a t i o n graphs from a c t u a l observa t i o n s of a l l o t h e r C e n o c o r i x a males are summarised, and i t i s seen t h a t the g e n e r a l p a t t e r n f o l l o w s t h a t of C_. b i f i d a ; s p e c i f i c d i f f e r e n c e s a r e a p p a r e n t l y owing t o d i f f e r e n c e s i n the p u l s e r a t e and average number of p u l s e s per  signal.  D u m o r t i e r (1963 b) has a s i m i l a r o b s e r v a t i o n on  signal  d u r a t i o n of E p h i p p i g e r p r o v i n c i a l i s ( Y e r s . )  (Orthoptera,  T e t t i g o n i o i d e a ) : s i g n a l d u r a t i o n f o l l o w s a curve o f h y p e r b o l i c shape. Moore ( 1 9 6 1 ) p u b l i s h e d sound spectrograms of s i g n a l produced b y a N o r t h American c o r i x i d , H e s p e r o c o r i x a donta (Hungfd.). i s 7-8  atopo-  The main f r e q u e n c y a r e a of these s i g n a l s  k c / s e c , which i s c l e a r l y h i g h e r t h a n i n any  Cenocorixa  s i g n a l . However, Moore kept the bugs i n a f i n g e r b o w l r e c o r d i n g was  and  done by microphone p r o t e c t e d from w e t t i n g by  a f i s h swimbladder; these f a c t o r s p o s s i b l y changed the frequency  of the sounds. F u r t h e r , Moore ( 1 9 6 1 ) s t a t e s t h a t  the p u l s e r a t e i n these s i g n a l s i s about 200 p u l s e s  per  second, but t h i s a p p a r e n t l y means the impact r a t e w i t h i n the pulses  [ i f the p u l s e i s d e f i n e d a c c o r d i n g t o Dumortier (1963  c)  156 8-i  1  10  1  20 Temperature  1  30 (°C)  F i g . 6 0 . Summary o f temperature e f f e c t on s i g n a l d u r a t i o n i n C e n o c o r i x a males. A: C. b i f i d a ; c o n t i n u o u s l i n e = observed c u r v e ; broken l i n e = expected curve ( f o r more e x p l a n a t i o n s see t e x t ) . B: observed c u r v e s ; a = C_. w i l e y a e ; b = _C. e x p l e t a ; c = C_. u t a h e n s i s ; d = _C. d a k o t e n s i s ; e = _C. a n d e r s o n i ; f = C_. b l a i s d e l l i ( f i r s t p a r t o f t h e s i g n a l o n l y ) ; g = C_. k u i t e r t i .  157  and t h e common concept i n b i o a c o u s t i c s ] . The s i g n a l s Moore ( 1 9 6 1 ) observed were produced by a male  specimen, and t h e y d i d n o t have any apparent  on o t h e r specimens  (females) i n the v i c i n i t y .  effect  Moore observed  f u r t h e r , t h a t t h e sound was produced by r u b b i n g t h e h i n d t i b i a e and t a r s i a l o n g t h e back o f t h e specimen. s p e c i e s , S i g a r a g r o s s o l i n e a t a Hungfd.,  Another  was observed t o s t r i d -  u l a t e i n a s i m i l a r way. T h i s mechanism o f sound p r o d u c t i o n was a l s o observed by F i n k e ( 1 9 6 8 ) i n s t u d i e s on S i g a r a ta,  stria-  and i n t h i s case b o t h males and females produced t h e s e  sounds, but t h e y were t o o f a i n t f o r s a t i s f a c t o r y r e c o r d i n g . I n t h e p r e s e n t s t u d y a l l C e n o c o r i x a s p e c i e s were observed t o produce t h e s e sounds i n two ways: i ) a l t e r n a t e movements of h i n d l e g s , i i ) s i m u l t a n e o u s movements o f h i n d l e g s . A s p e c t r o g r a m o f t h e s e sounds i s shown i n F i g . 3 0 . No s p e c i e s specificity  was observed and p l a y b a c k experiments  utilising  t h e s e sounds d i d n o t i n i t i a t e any response o f males o r f e males. The bugs were observed t o produce these sounds a t any time o f t h e y e a r . These sounds appear t o be a r e s u l t o f c l e a n i n g movements and a r e n o t t r u e s t r i d u l a t o r y  signals.  The movements a r e a p p a r e n t l y made t o c l e a n and r e a r r a n g e t h e lateral  abdominal h a i r s t h a t a r e i m p o r t a n t i n m a i n t a i n i n g  the  a i r bubble between t h e wings and t h e abdominal dorsum  for  r e s p i r a t i o n (Popham, I96O; P a r s o n s , 1 9 7 0 ) . L e s t o n and P r i n g l e ( 1 9 6 3 ) adhere t o t h e o l d concept  t h a t t h e use o f p a l a r pegs i n p o s s i b l e s t r i d u l a t o r y mechanism has n o t been d i s p r o v e n . They r e f e r t o s p e c i e s which have n o t been observed t o s t r i d u l a t e , and suggest t h a t t h e s i g n a l s o f  these s p e c i e s might be too f a i n t t o be r e c o r d e d .  In fact i t  i s t r u e t h a t a l l s p e c i e s of C o r i x i d a e can o f t e n be  observed  t o rub t h e i r p a l a e a g a i n s t each o t h e r or the r o s t r u m . Howe v e r , t h i s seems t o be n o t h i n g more t h a n a k i n d of c l e a n i n g a c t i v i t y , and sounds produced i n t h i s way would p r o b a b l y f a r too f a i n t t o have any s i g n i f i c a n c e the bugs, e s p e c i a l l y  i n the b e h a v i o r  be  of  when much more i n t e n s i v e sounds, p r o d -  uced by the r u b b i n g of the h i n d l e g s , appear t o be s i d e products  o f c l e a n i n g movements.and w i t h o u t b e h a v i o r a l  significance. I n C e n o c o r i x a the use of p a l a r pegs i n s t r i d u l a t i o n i s i m p o s s i b l e s i n c e o n l y the males have these pegs, y e t males and females s t r i d u l a t e .  both  I n s i m i l a r genera, the p a l a r  pegs of the males a r e used f o r c l a s p i n g the female d u r i n g c o p u l a t i o n (Popham, 1 9 6 1 ) : the pegs are p l a c e d under the curved l o n g i t u d i a l  r i d g e of the l a t e r a l f l a n g e oh the female  h e m i e l y t r o n ; the two another,  sexes are thus f i r m l y a t t a c h e d t o  and a r e a b l e t o swim w h i l e i n c o p u l a .  one  159  2. L i f e c y c l e , s e x u a l m a t u r a t i o n , and D e t a i l e d study on l i f e  stridulation  c y c l e o f f o u r s p e c i e s was  out i n o r d e r t o f i n d out how  stridulation  s e x u a l m a t u r i t y i n the genus C e n o c o r i x a .  carried  correlates with The  study showed  t h a t i n the i n t e r i o r of B r i t i s h Columbia both C_. b i f i d a  and  C_. e x p l e t a commonly have a p a r t i a l second g e n e r a t i o n p e r summer. However, i n f a v o u r a b l e c i r c u m s t a n c e s  a complete  second g e n e r a t i o n and even a p a r t i a l t h i r d g e n e r a t i o n be produced, as was LB2.  The  can  shown of C_. • e x p l e t a i n the water body  f a i l u r e o f Q. b i f i d a t o produce more than  g e n e r a t i o n i n LB2 was  one  a p p a r e n t l y owing t o i n c r e a s i n g s a l -  i n i t y which d u r i n g June and J u l y k i l l e d l a r v a e of the second generation. H u n g e r f o r d (1948) s t a t e s t h a t i n g e n e r a l N o r t h A m e r i c a n C o r i x i d a e produce one ing  on temperature.  or two g e n e r a t i o n s p e r summer, depend-  Larsen  ( 1 9 3 8 ) , C r i s p ( 1 9 6 2 ) , and Young  ( 1 9 6 5 ) have s t u d i e d the l i f e c y c l e s of s e v e r a l European C o r i x i d a e , and  some s p e c i e s have been observed  t o have o n l y  one g e n e r a t i o n w h i l e o t h e r s a p p a r e n t l y produce a p a r t i a l second g e n e r a t i o n . S i m i l a r l y , Pajunen (1970) observed s p e c i e s of c o r i x i d s  Pajunen and J a n s s o n (1969)  and  a p a r t i a l second g e n e r a t i o n i n two  l i v i n g i n r o c k p o o l s i n the a r c h i p e l a g o  of s o u t h e r n F i n l a n d . However, n e i t h e r a completed second g e n e r a t i o n (as i n C_. a n d e r s o n i i n the P a c i f i c Westcoast) nor a p a r t i a l t h i r d g e n e r a t i o n (C_. e x p l e t a i n LB2)  have been  r e p o r t e d p r e v i o u s l y . By comparing the temperature d a t a the l a k e s , s t u d i e d d u r i n g the p r e s e n t work ( F i g s .  on  34-35), i t  can be seen t h a t LB2 g e n e r a l l y had a s l i g h t l y h i g h e r temper-  160  a t u r e than o t h e r l a k e s . Thus the p a r t i a l t h i r d  generation  i n C_. e x p l e t a o c c u r r e d i n the warmest l a k e . P r i o r t o the p r e s e n t work no d e t a i l e d s t u d y of the sequence of g e n e r a t i o n s based on the phenology of the  diff-  e r e n t l a r v a l i n s t a r s has been p u b l i s h e d . A p p a r e n t l y t h i s i s because the f i v e l a r v a l i n s t a r s a r e commonly found i n the l a k e s throughout  together  the summer, and the l a r v a e b e l o n g i n g  t o s e p a r a t e g e n e r a t i o n s may  be d i f f i c u l t t o s e p a r a t e .  The  l a c k of i d e n t i f i c a t i o n keys f o r l a r v a e a l s o has not been conducive was  t o such s t u d i e s . I n the p r e s e n t work, however, i t  p o s s i b l e t o i d e n t i f y the l a r v a e f o l l o w i n g Scudder ( 1 9 6 6 ) ,  and changes i n the r e l a t i v e numbers of d i f f e r e n t l a r v a l i n s t a r s i n the samples were c o n s i d e r e d t o be a r e l i a b l e I n d i c a t o r i n p l a c i n g the l a r v a e i n t o p r o p e r g e n e r a t i o n s . sequence of g e n e r a t i o n s was  The  a l s o f o l l o w e d by s t u d y i n g the  gonad development, the method used i n p r e v i o u s s t u d i e s on l i f e c y c l e s , but the l a r v a l study made more a c c u r a t e  state-  ments p o s s i b l e . The  study of the o v a r i e s i n C e n o c o r i x a  w i n t e r e d females  showed t h a t over-  become s e x u a l l y mature soon a f t e r I c e  break-  up i n the i n t e r i o r o f B r i t i s h Columbia, w h i l e a t the c o a s t m a t u r i t y i s reached  i n March. I n a d d i t i o n , C_. b i f i d a and _C.  e x p l e t a were observed  t o f l y a c t i v e l y i n e a r l y May  and C_. b l a i s d e l l i was  found t o f l y throughout  1969,  the summer of  1970, when t h e y were b r e e d i n g . I n c o n t r a s t , r o c k p o o l s p e c i e s of s o u t h e r n F i n l a n d have a s h o r t d i s p e r s a l p e r i o d b e f o r e a t t a i n i n g s e x u a l m a t u r i t y (Pajunen and Jansson, On the o t h e r hand, Young (1965) observed m a t u r a t i o n  of  1969).  161 f e m a l e s i n some s p e c i e s t o occur b e f o r e break-up i n England. Sexual maturation  o f females o f t h e i n i t i a l p a r t .of t h e  f i r s t generation i n Cenocorixa  was observed t o t a k e about  one week. S i m i l a r l y , Pajunen ( 1 9 7 0 ) observed young females of C a l l i c o r i x a producta  (Reut.) and A r c t o c o r i s a c a r i n a t a (C.  S a h i b . ) t o have c h o r i o n a t e d . e g g s  w i t h i n a p e r i o d o f 10-14  days. The l a t e r p a r t o f t h e f i r s t g e n e r a t i o n i n C e n o c o r i x a was observed t o remain s e x u a l l y immature i n t h e i n t e r i o r o f B r i t i s h Columbia. Both Young ( 1 9 6 5 ) and Pajunen ( 1 9 7 0 ) , who made s i m i l a r o b s e r v a t i o n s , e x p l a i n e d t h i s i n c o n n e c t i o n photoperiod.  According  t o Young ( 1 9 6 5 )  with  t h e r e i s no diapause  i n t h e o v a r i a n development because a d u l t females were observed to  mature and l a y eggs i n t h e l a b o r a t o r y a t a l l times, o f t h e  y e a r when under e x p e r i m e n t a l  c o n d i t i o n s o f 16 hours photo-  p e r i o d and t e m p e r a t u r e s o f 12-32°C. F u r t h e r , he s t a t e s t h a t the c o n t r o l o f t h e i n i t i a l development o f t h e o v a r i e s p r o b a b l y depends on p h o t o p e r i o d i c e f f e c t . However, some o f h i s own r e s u l t s a r e i n c o n s i s t e n t w i t h t h i s s u g g e s t i o n : He n o t i c e d for  example-2in  Sigara s c o t t i (Fieb.), l i v i n g i n a lake with  wide s h a l l o w a r e a s , t h a t when t h e water l e v e l dropped some p o o l s were formed a l o n g t h e l a k e : t h e f i r s t a d u l t s o f t h e • f i r s t summer g e n e r a t i o n emerged more t h a n two weeks e a r l i e r i n these p o o l s than i n t h e l a k e i t s e l f . F u r t h e r , he observed t h a t i n none o f t h e specimens i n t h e p o o l s d i d o v a r i a n matura t i o n take p l a c e , whereas i n t h e main l a k e i n e a r l y J u l y i t did!  I n t h i s case a t l e a s t , p h o t o p e r i o d  c o u l d not have any-  t h i n g t o do w i t h t h e d i f f e r e n c e i n t h e o v a r i a n development. According  t o Pajunen ( 1 9 7 0 ) a r r e s t e d o v a r i a n development  162  appears i n e a r l y J u l y , which i s near t h e m i d d l e o f t h e summer i n s o u t h e r n F i n l a n d . F u r t h e r , he s t a t e s t h a t t h i s a r r e s t depends on p h o t o p e r i o d and t h a t t h e a d a p t i v e v a l u e o f o v a r i a n a r r e s t i n t h i s p a r t i c u l a r case must l i e i n t h e l i m i t a t i o n o f p o p u l a t i o n s i z e : h i g h r e p r o d u c t i v e c a p a c i t y o f c o r i x i d s would boost t h e d e n s i t y o f t h e p o p u l a t i o n s beyond t h e l e v e l s o f food resources i n the rock pool  environment.  The r e s u l t s o f t h e p r e s e n t s t u d y showed d i f f e r e n c e s between t h e l a k e s i n t h e i n t e r i o r o f B r i t i s h Columbia i n t h e t i m i n g o f t h e a r r e s t i n o v a r i a n development, but t h i s  cannot  r e f l e c t d i f f e r e n c e s i n t h e p h o t o p e r i o d : a l l l a k e s were w i t h i n a r e l a t i v e l y small geographic  a r e a , some o f them o n l y 1-2  k i l o m e t r e s from each o t h e r . F u r t h e r , t h e l a k e where mature females were observed l a t e s t (LB2), was about 1 0 0 km f u r t h e r s o u t h t h a n t h e o t h e r s , and thus had a s h o r t e r p h o t o p e r i o d t h a n t h e o t h e r s throughout  t h e summer. A d d i t i o n a l i n f o r m a t i o n  i n support o f t h i s c o n t e n t i o n was o b t a i n e d from Soap Lake, which i s l o c a t e d i n Washington, about 5 0 0 km south from t h e main study a r e a . Here _C. e x p l e t a was found t o be b r e e d i n g as l a t e as 29 August 1969, and so here a g a i n t h e p h o t o p e r i o d i s shorter than i n the Cari'boo-Chilcotin area of B r i t i s h F u r t h e r , t h e experiment  Columbia.  c a r r i e d out w i t h C_. b i f i d a on 8 and  16 hours p h o t o p e r i o d , showed t h a t a l t h o u g h not every  female,  a t l e a s t some o f t h e females i n both s h o r t and l o n g photop e r i o d became s e x u a l l y mature a t t h e same time i n l a b o r a t o r y c o n d i t i o n s , and thus i n d e p e n d e n t l y o f t h e p h o t o p e r i o d . When d i f f e r e n c e s observed i n t h e f i e l d s t u d y i i . n t h e t i m i n g o f t h e a r r e s t i n o v a r i a n development a r e compared  163  w i t h the p r o d u c t i v i t y of the l a k e s , a c l e a r  correlation  between the two i s found: i n low p r o d u c t i v i t y l a k e s a l l females were found t o show o v a r i a n developmental  arrest i n  early July, while i n high p r o d u c t i v i t y lakes reproductive females were observed  u n t i l the end of J u l y . I n l a k e s w i t h  v e r y h i g h p r o d u c t i v i t y , r e p r o d u c t i v e females were  observed  as l a t e as end of August. I t I s known t h a t s t a r v i n g i n s e c t s do not develop  eggs ( c f . Johansson, 1958; 1 9 6 4 ) , and thus i n  low p r o d u c t i v i t y l a k e s i t seems p r o b a b l e t h a t t h e r e i s a s h o r t a g e of f o o d . However, the e x a c t f o o d u t i l i s e d i n these low p r o d u c t i v i t y l a k e s i s unknown. I n the h i g h p r o d u c t i v i t y l a k e s b o t h C_. b i f i d a  and _C.  e x p l e t a f e e d on Diaptomus s i c i l i s Forbes (Scudder,  personal  comm.), a copepod t h a t i s absent from the low p r o d u c t i v i t y l a k e s (Scudder,  1969 b ) . Zwart ( 1 9 6 5 ) suggests  that  almost  any form of s m a l l l i v i n g animal would be adequate food f o r c o r i x i d s g e n e r a l l y , but a t l e a s t i n some cases  supply  plankton  animals seem t o be p r e f e r r e d . I t i s most l i k e l y i n the S i g a r a scotti  s t u d i e d by Young ( 1 9 6 5 ) , t h a t the specimens i n the  p o o l s c u t o f f from the main l a k e , d i d not have an adequate f o o d s u p p l y , and so remained s e x u a l l y immature,, whereas those i n the main l a k e were not s h o r t of f o o d . A l t h o u g h (1970) s t a t e s t h a t o v a r i a n a r r e s t prevents  Pajunen  overpopulation  i n r o c k p o o l s , i t i s p o s s i b l e - t h a t because r o c k p o o l s are not v e r y p r o d u c t i v e water b o d i e s , t h a t i t i s the amount of food t h a t l i m i t s  insufficient  the siz:e_of p o p u l a t i o n s by  cutting  o f f the development o f the o v a r i e s . Thus, the p r e s e n t study suggests t h a t p h o t o p e r i o d i s not  164  the c r i t i c a l f a c t o r i n t h e o v a r i a n d e v e l o p m e n t a l a r r e s t i n the genus C e n o c o r i x a .  However, because t h e time o f t h e a r r e s t  i n t t h e h i g h p r o d u c t i v i t y l a k e s does n o t c o i n c i d e w i t h any drop i n t h e a v a i l a b i l i t y  o f copepods, t h e l a c k o f food may  not be t h e o n l y e n v i r o n m e n t a l  f a c t o r envolved.  The temper-  a t u r e r e c o r d s f o r t h e l a k e s show t h a t t h e a r r e s t i s n o t c o r r e l a t e d w i t h an obvious.decrease  i n temperature: temper-  a t u r e does n o t s t a r t t o drop s i g n i f i c a n t l y u n t i l l a t e tember. O v a r i a n development i s p r o b a b l y  Sep-  i n f l u e n c e d by s e v e r a l  f a c t o r s . Food s u p p l y , temperature, and p h o t o p e r i o d a r e f a c t o r s t h a t may be i m p o r t a n t  i n some i n s t a n c e s , b u t t h i s  a s p e c t needs f u r t h e r i n v e s t i g a t i o n s . Sexual maturation  o f C e n o c o r i x a males was observed t o  f o l l o w g e n e r a l l y t h e same p a t t e r n as t h e m a t u r a t i o n females,  but w i t h t h e f o l l o w i n g d i f f e r e n c e s : newly  of the emerged  males o f t h e i n i t i a l p a r t o f t h e f i r s t g e n e r a t i o n were sexu a l l y mature a t t h e time o f emergence, and a t l e a s t some o f the o v e r w i n t e r i n g males reached s e x u a l m a t u r i t y i n l a t e rather that e a r l y spring. Larsen  fall,  (193<3) s t u d i e d s e x u a l matur-  a t i o n o f c o r i x i d s i n Sweden, and observed mature sperm i n the t e s t e s g e n e r a l l y d u r i n g s p r i n g , but i n one s p e c i e s , C o r i x a d e n t i p e s Thorns., he a l s o d e t e c t e d  sperm i n t h e t e s t e s  i n September. On t h e o t h e r hand, Young (1965) s t a t e s t h a t sperm i s formed d u r i n g summer and autumn i n t h e o v e r w i n t e r i n g males, s t o r e d i n t h e seminal v e s i c l e s u n t i l s p r i n g , and t h e t e s t e s a r e i n a c t i v e i n t h e s p r i n g ! A l s o Pajunen (1970)  claims  t h a t sperm was found i n t h e seminal v e s i c l e s o f t h e l a t e summer specimens a t t h e time when o v a r i a n development i n  165  females was a l r e a d y a r r e s t e d . N e i t h e r Young ( 1 9 6 5 ) nor Pajunen methods they adopted  (1970) e x p l a i n the  i n i n v e s t i g a t i n g t h e presence  o f sperm.)  i n t h e s e m i n a l v e s i c l e s . However, w i t h t h e squashing method used i n most of t h e p r e s e n t study, i t was n o t p o s s i b l e t o observe sperm i n t h e s e m i n a l v e s i c l e s because i n C o r i x i d a e t h i s organ i s surrounded  by a thick: l a y e r o f c o n n e c t i v e  t i s s u e : i f sperm e x i s t s i n t h e s e m i n a l v e s i c l e i t w i l l appear v e r y s i m i l a r ttb t h e f i b r e s o f t h e s u r r o u n d i n g c o n n e c t i v e t i s s u e , and cannot  be d i s t i n g u i s h e d . A l s o i n t h e t e s t e s them-  s e l v e s t h e r e a r e some s t r u c t u r e s which appear v e r y much l i k e mature sperm and some p r a c t i c e is- needed t o d i s t i n g u i s h t h e presence  o f mature sperm. However, t h e r e s u l t s o b t a i n e d w i t h  the squashing method were checked  by making s e r i a l s e c t i o n s  of t h e t e s t e s . Thus, a l t h o u g h t h e s e m i n a l v e s i c l e s c o u l d n o t be s t u d i e d i n squash p r e p a r a t i o n s , i t was shown t h a t i f t h e t e t i c u l a r f o l l i c l e s d i d not c o n t a i n spermatids a t t h e i r developmental  late  stage ( F i g . 40 D), t h e s e m i n a l v e s i c l e s d i d n o t  c o n t a i n any sperm, and so t h e specimen was s e x u a l l y immature. I n mature i n d i v i d u a l s a l l o f t h e stages o f spermatog e n e s i s were c l e a r l y v i s i b l e i n t h e f o l l i c l e s i n t h e i n i t i a l p a r t o f t h e f i r s t summer g e n e r a t i o n and l a t e f a l l I n t h e overwintered specimens i t o f t e n was observed  insects. that  mature sperm c o u l d n o t be d e t e c t e d i n t h e t e s t e s , b u t c o u l d be found i n t h e s e m i n a l v e s i c l e s i n t h e s e r i a l s e c t i o n s . Howe v e r , t h e presence  o f v e r y l a r g e numbers o f d e v e l o p i n g c y s t s  w i t h a l l o t h e r stages o f spermatogenesis  i n d i c a t e that the  t e s t e s were by no means i n a c t i v e as s t a t e d by Young ( 1 9 6 5 ) .  166  I t would be more n a t u r a l t o assume t h a t the d e v e l o p i n g f i l l e d the f o l l i c l e s and  cysts  s i m p l y pushed the mature sperm i n t o  the s e m i n a l v e s i c l e s . T h i s i s a l s o s u p p o r t e d by the f a c t t h a t sometimes the sperm appeared t o be s t i l l i n bundles i n the s e m i n a l v e s i c l e s i n the s e r i a l s e c t i o n s . F u r t h e r ,  specimens  s t u d i e d i n l a t e summer, at the time of o v a r i a n a r r e s t i n f e m a l e s , showed t h a t the t e s t i c u l a r f o l l i c l e s were f i l l e d w i t h c y s t s i n stages of m e i b t i c d i v i s i o n and w i t h s p e r m a t i d s i n t h e i r e a r l y d e v e l o p m e n t a l stage ( F i g . 4 4 ) , but no s t a g e s were found. A t t h i s time, was  therefore,  further  spermatogenesis  also arrested. The  r e a s o n f o r the a r r e s t of spermatogenesis i s not  e a s i l y explained.  I t occurred  simultaneously  w i t h the a r r e s t  of o 8 g e n e s i s i n females i n v a r i o u s lak.es. I n g e n e r a l ,  however,  i n s u f f i c i e n t nourishment i n male i n s e c t s does not u s u a l l y p r e vent sexual maturity,  but m e r e l y reduces the s i z e of the t e s -  t e s (Johansson, 1 9 6 4 ) . However, Geer ( 1 9 6 7 ) and  Geer and  New-  burgh ( I 9 7 O ) have shown w i t h D r o s o p h i l a melanogaster t h a t  the  development of mature sperm i s dependent upon d i e t a r y f a c t o r s . Thus, i t may  be t h a t the reasons f o r the a r r e s t of spermato-  g e n e s i s are the same as f o r the a r r e s t of o o g e n e s i s , and  at  l e a s t p a r t l y owing t o d i e t d e f i c i e n c i e s . I t i s not known why  the males become s e x u a l l y mature i n l a t e f a l l w h i l e f e -  males remain s e x u a l l y immature. Almost a l l p r e v i o u s  s t u d i e s on s t r i d u l a t i o n of  s t a t e t h a t s i g n a l s are produced o n l y d u r i n g the season, i . e . s p r i n g and 1951;  Leston,  1955;  breeding  e a r l y summer ( M i t i s , 1936;  Southwood and L e s t o n ,  1959;  Corixidae  Schaller,  Leston  and  167  P r i n g l e , 1 9 6 3 ; F i n k e , 1 9 6 8 ) . The o n l y p r e v i o u s p u b l i c a t i o n mentioning s t r i d u l a t i o n during the f a l l i s Larsen  (1938):  C o r i x a d e n t i p e s was observed t o s t r i d u l a t e i n September (Larsen a l s o detected  sperm.'.in t h e t e s t e s o f t h i s  a t t h e same t i m e ) . I n t h e p r e s e n t the s t r i d u l a t i o n o f C e n o c o r i x a  species  study i t was shown t h a t  males c o r r e l a t e s w i t h  sex-  u a l m a t u r i t y . Thus, males o f C o r i x i d a e w i l l s t r i d u l a t e side of the breeding  out-  season.  I n some o t h e r i n s e c t s s t r i d u l a t i o n has been r e p o r t e d s e v e r a l months before a c t u a l mating. F o r i n s t a n c e Van T a s s e l (1965) r e p o r t s b e e t l e s o f t h e genus Berosus  (Hydrophilidae)  t o s t r i d u l a t e when brought i n t o t h e l a b o r a t o r y i n January. The p r e s e n c e o f mature sperm was n o t i n v e s t i g a t e d i n t h a t study, b u t because t h e a u t h o r  r e p o r t s t h e males t o have  attempted c o p u l a t i o n a t t h e time t h a t t h e y s t r i d u l a t e d ,  they  p r o b a b l y were s e x u a l l y mature. Females, however, o b v i o u s l y reached s e x u a l m a t u r i t y s e v e r a l months l a t e r because  success-  f u l c o p u l a t i o n s were n o t observed u n t i l May. The  f a c t t h a t s t r i d u l a t i o n i n C e n o c o r i x a males i s c o r r e -  l a t e d w i t h s e x u a l m a t u r i t y , was a l s o shown w i t h specimens taken i n t o the l a b o r a t o r y i n l a t e f a l l .  Such males  strid-  u l a t e d and made attempts a t c o p u l a t i o n , but females always r e j e c t e d t h e males a t t h i s time. Two t o t h r e e weeks l a t e r some o f t h e females reached s e x u a l m a t u r i t y ,  apparently  because t h e room temperature was h i g h enough t o a l l o w t h i s , and t h e food s u p p l y ( f r o z e n b r i n e shrimps) was s u f f i c i e n t . A t t h i s time t h e males were a c c e p t e d  and c o p u l a t i o n s were  s u c c e s s f u l . The f a c t t h a t no c o p u l a t i o n s occur n o r m a l l y I n  168 l a t e f a l l i n the n a t u r a l environments was  demonstrated  by  t a k i n g female i n s e c t s from the f i e l d and k e e p i n g them a t room temperature w i t h o u t males: some of the females matured i n about t h r e e weeks and l a i d eggs, but no l a r v a e hatched from t h e s e eggs and no embryonic  development was d e t e c t e d .  The females seem not t o have mated and thus t h e y do not s t o r e sperm over w i n t e r i n the r e c e p t a c u l u m s e m i n i s . S t o r i n g sperm over w i n t e r i n the r e c e p t a c u l u m s e m i n i s i s a common phenomenon i n temperate  s o c i a l Hymenoptera ( R i c h a r d s , 1 9 6 1 ) .  The q u e s t i o n of how  s e x u a l m a t u r i t y i n C e n o c o r i x a males  i n d u c e s t h e s e bugs t o s t r i d u l a t e was not i n v e s t i g a t e d i n the p r e s e n t study. However, t h e r e have been attempts t o s t u d y t h i s p r e v i o u s l y i n other i n s e c t s . H a s k e l l ( i 9 6 0 ) , f o r instance, r e p o r t s t h a t c a s t r a t e d males of g r a s s h o p p e r s ( O r t h o p t e r a , T r u x a l i n a e ) s t r i d u l a t e , p e r f o r m c o u r t s h i p d i s p l a y , and  cop-  u l a t e . A c c o r d i n g t o t h i s , a c t u a l presence o f sperm i s . not necessary i n these grasshoppers. The a n n u a l rhythm of s t r i d u l a t i o n i n C e n o c o r i x a females c o u l d not be s t u d i e d i n the f i e l d . However, b e h a v i o r a l experiments showed t h a t o n l y females w i t h c h o r i o n a t e d eggs i n the l a t e r a l o v i d u c t s responded  t o the male s i g n a l s by a n s w e r i n g ,  p r o v i d i n g t h a t t h e y had not mated r e c e n t l y . Thus, the  strid-  u l a t i o n of females c o r r e l a t e s b o t h w i t h s e x u a l m a t u r i t y and a "need" f o r a mate. The q u e s t i o n of what changes the b e h a v i o r of a r e c e p t i v e female t o an u n r e c e p t i v e one was not s t u d i e d i n d e t a i l i n the p r e s e n t work. However, i t was n o t i c e d t h a t the r e c e p t i v e females always had c h o r i o n a t e d eggs i n the l a t e r a l o v i -  169  d u c t s , and no embryonic laid  development o c c u r r e d i n the eggs  by these f e m a l e s . M a t i n g changed the females  from  r e c e p t i v e t o u n r e c e p t i v e , and eggs l a i d by these females developed n o r m a l l y and l a r v a e h a t c h e d . I t was a l s o  observed  t h a t i n t e r r u p t e d c o p u l a t i o n s ( a l l o w e d t o l a s t o n l y 1-2 seconds) were enough t o make the females u n r e c e p t i v e . Whether or not sperm was  t r a n s f e r r e d i n these c o p u l a t i o n s was  not  s t u d i e d . The s t i m u l u s f o r females t o be u n r e c e p t i v e c o u l d thus be c h e m i c a l , t a c t i l e ,  or b o t h .  I t has been shown t h a t the females of c e r t a i n g r a s s hoppers to  ( H a s k e l l , i 9 6 0 ) and k a t y d i d s (Spooner, 1964) seem  be r e c e p t i v e t o males i n a. way  s i m i l a r to Cenocorixa f e -  males: a mated female i s not r e c e p t i v e u n t i l a f t e r  several  o v i p o s i t i o n s . H a s k e l l ( i 9 6 0 ) c l a i m s t h a t the presence of sperm i n the r e c e p t a c u l u m s e m i n i s has a c h e m i c a l e f f e c t upon the female. However, i t s h o u l d be noted t h a t sperm or a c c e s s o r y g l a n d m a t e r i a l or b o t h do not always have t o be l o c a t e d i n the r e c e p t a c u l u m s e m i n i s t o be c h e m i c a l l y e f f e c t i v e . Davey ( 1 9 5 8 ) has shown t h a t the spermatophore  i n Rhodnius  (Hemiptera, H e t e r o p t e r a , R e d u v i i d a e ) i n d u c e s r h y t h m i c c o n t r a c t i o n s of the bursa c o p u l a t r i x , and i n D r o s o p h i l a the w a l l s of the v a g i n a s e c r e t e f l u i d o f an i n s e m i n a t i o n r e a c t i o n ( P a t t e r s o n , 1946; Lee, 1950) soon a f t e r c o i t u s and t h i s s t a r t b e f o r e c o p u l a t i o n i s completed  ( P a t t e r s o n and  may  Stone,  1 9 5 2 ) . I n s e c t g e n i t a l i a have sense organs which are i m p o r t a n t i n mating (Scudder, 1971) and the f u n c t i o n of t h e s e c o u l d be s u f f i c i e n t t o t e r m i n a t e the response of the female. Spooner ( 1 9 6 4 ) c l a i m s t h a t i n k a t y d i d s the presence of eggs i n the  170 o v a r i e s determines the p o s i t i v e response of f e m a l e s : as soon as t h e eggs move t o the l a t e r a l o v i d u c t s the response i s i n h i b i t e d . I n c o n t r a s t , i n C e n o c o r i x a the presence of eggs i n the l a t e r a l o v i d u c t s seems t o be e s s e n t i a l f o r r e c e p t i v e ness.  :.,:  171  3. S t r i d u l a t o r y b e h a v i o r O b s e r v a t i o n s on t h e s t r i d u l a t o r y b e h a v i o r o f C e n o c o r i x a males i n d i c a t e t h a t s t r i d u l a t i o n commences s p o n t a n e o u s l y , p r o v i d i n g t h e males a r e s e x u a l l y mature. I n g e n e r a l c l a s s i f i c a t i o n s of the f u n c t i o n of i n s e c t signals  (Dumortier,  1963 c; A l e x a n d e r , 1967; 1968) t h i s would be c l a s s i f i e d as a c a l l i n g s i g n a l , and i t s f u n c t i o n would be t o f a c i l i t a t e p a i r - f o r m a t i o n by a t t r a c t i n g c o n s p e c i f i c females. The expe r i m e n t s c o n f i r m e d t h a t t h i s i s t h e case i n C e n o c o r i x a . Howe v e r , experiments a l s o showed t h a t s i g n a l s o f males would o f t e n s t i m u l a t e o t h e r males t o s t r i d u l a t e . D i f f e r e n c e s were d e t e c t e d between t h e s p e c i e s i n t h e i r r e a d i n e s s t o answer v a r i o u s s i g n a l s . When c o n s p e c i f i c male s i g n a l s were used (Fig.  5 2 , Table V I I I ) , some, b u t n o t a l l C e n o c o r i x a s p e c i e s  r e a d i l y answered t h e s e s i g n a l s . F u r t h e r , i n cases when c e r t a i n s p e c i e s a r e a b l e t o produce two d i f f e r e n t ( f i r s t p a r t o f t h e c a l l a l o n e o r complete  calls  s i g n a l ) , t h e males  answered t h e slow p u l s a t e d f i r s t p a r t more r e a d i l y t h a n a complete  s i g n a l ( e . g . C_. a n d e r s o n i : Table V I I I ) .  Both spontaneous and sound evoked s t r i d u l a t i o n has been observed i n male C o r i x i d a e p r e v i o u s l y ( S c h a l l e r , 1 9 5 1 ; L e s t o n , 1955; L e s t o n and P r i n g l e , 1963; F i n k e , 1 9 6 8 ) , and t h e s i g n a l s have been c l a s s i f i e d m o s t l y as c a l l i n g s i g n a l s . F u r t h e r , a v e r y commonly h e l d concept i s t h a t a c o u r t s h i p s i g n a l as d i s t i n c t from a c a l l i n g s i g n a l a l s o e x i s t s : M i t i s  (1936)  observed i n S i g a r a s t r i a t a , t h a t a male o b s e r v i n g a female, s t a r t e d s t r i d u l a t i n g very a c t i v e l y w i t h shortened  intervals  and l o n g e r s i g n a l s . A l s o L e s t o n ( 1 9 5 5 ) , Southwood and L e s t o n  172  ( 1 9 5 9 ) , and  L e s t o n and  s h i p s i g n a l has  P r i n g l e (1963) c l a i m that a court-  been observed i n c o r i x i d s , but t h e y do  e x p l a i n the d i f f e r e n c e between the s i g n a l s b e l o n g i n g  not  to  the  c a l l i n g or c o u r t s h i p c a t e g o r i e s . H a s k e l l ( 1 9 6 1 ) s t a t e s t h a t male;-, c o r i x i d s - can g e n e r a l l y produce two suggested t h a t one  s i g n a l s , and i t i s  i s a c a l l i n g s i g n a l , the other a c o u r t -  s h i p s i g n a l , a l t h o u g h t h i s has  y e t t o be  I n the p r e s e n t study i t was  confirmed.  f r e q u e n t l y observed t h a t  as  w e l l as s t r i d u l a t o r y s i g n a l s , a v i s u a l s t i m u l u s from a male, female, or specimen of a n o t h e r s p e c i e s i n d u c e d C e n o c o r i x a males t o s t r i d u l a t e . No d i f f e r e n c e was  detected  i n the  s t r u c t u r e of t h e s e response s i g n a l s except .in cases when the response, s i g n a l was  o n l y a p a r t of the normal c a l l  or  c a l l i n g s i g n a l , which o f t e n , but not always happened i n (J. a n d e r s o n i ,  (J. u t a h e n s i s ,  and  CJ. b l a i s d e l l i . A c c o r d i n g  to  the d e f i n i t i o n of a c o u r t s h i p s i g n a l [Dumortier (1963 c ) : a d i s p l a y of the male, s e t o f f by a s t i m u l u s  from the  female],  ' t h i s i n d u c e d s i g n a l i s not a c o u r t s h i p s i g n a l . L e s t o n and of c o r i x i d s may  P r i n g l e ( 1 9 6 3 ) s t a t e t h a t the c a l l i n g s i g n a l i n c l u d e r i v a l r y or t e r r i t o r i a l f u n c t i o n .  F u r t h e r , when movements of C_. b i f i d a males were compared i n the s i t u a t i o n s where the males were a l o n e or exposed t o a s t r i d u l a t o r y s t i m u l u s , i t was  shown t h a t s i g n i f i c a n t l y more  swimming ( e s p e c i a l l y s h o r t range swimming) o c c u r r e d s t r i d u l a t o r y s i g n a l s were p r e s e n t . of (J_. b i f i d a and was  In observations  (J. b l a i s d e l l i i t was  o f t e n f o l l o w e d by nudging and  found t h a t  chasing  when on males  stridulation  b e h a v i o r which  s e r v e s t o space out i n d i v i d u a l s . T h i s suggests t h a t the  strid-  173  u l a t i o n i n C e n o c o r i x a f u n c t i o n s as an a g o n i s t i c  signal.  S i m i l a r l y , L e s t o n and P r i n g l e ( 1 9 6 3 ) r e p o r t t h a t S i g a r a d o r s a l i s (Leach.) males, s t r i d u l a t i n g a l t e r n a t e l y , move towards each o t h e r u n t i l t h e i r heads come t o g e t h e r , and one of them f i n a l l y nudges the o t h e r one away. I n £.  bifida  and C_. b l a i s d e l l i , i f the specimens were w i t h i n v i s u a l range o f each o t h e r , t h e y d i d not move towards each o t h e r d u r i n g the s i g n a l l i n g w h i c h preceded the nudging. I n C e n o c o r i x a , the s i g n a l s produced i n a g o n i s t i c  situ-  a t i o n s , d i d not u s u a l l y d i f f e r s t r u c t u r a l l y from s p o n t a n e o u s l y produced c a l l i n g s i g n a l s , a l t h o u g h t h e i r f u n c t i o n a p p a r e n t l y i s d i f f e r e n t . I n c o n t r a s t , O r t h o p t e r a n s have a more h i g h l y developed a c o u s t i c communicating system o f t e n w i t h s t r u c t u r a l l y d i f f e r e n t s i g n a l s f o r d i f f e r e n t purposes ( D u m o r t i e r , 1963 c ) . However, the f u n c t i o n of the a g o n i s t i c s i g n a l s of C e n o c o r i x a males seems t o be the same as the f u n c t i o n of a r i v a l ' s song i n D u m o r t i e r ' s (1963 c) c l a s s i f i c a t i o n : an emiss i o n produced, u s u a l l y a l t e r n a t e l y , by two i n d i v i d u a l s a s h o r t d i s t a n c e from each o t h e r , d e n o t i n g the s o - c a l l e d r i v a l r y or t e r r i t o r i a l behavior. I n _C. b i f i d a , when a s t r i d u l a t i n g male was within^a-.:few c e n t i m e t r e s o f an u n r e c e p t i v e female, a p p a r e n t l y a p p r o a c h i n g the l a t t e r , the female was observed t o swim away from the c a l l i n g male (escape) or d i s t u r b the male by swimming towards it  ( a g o n i s t i c b e h a v i o r ) . A r e c e p t i v e f e m a l e , on the o t h e r  hand, w i t h i n the range of the sound of the c a l l i n g  male,  would s t a y m o t i o n l e s s and s t r i d u l a t e i n answer t o the male call.  I n o t h e r words, a r e c e p t i v e female produced an  agreement  174  signal  [ a c c o r d i n g t o c l a s s i f i c a t i o n of Dumortier ( 1 9 6 3 c ) ] .  Males were observed t o o r i e n t a t e d i r e c t l y t o the female a c c o r d i n g t o t h i s agreement s i g n a l . No t r u e c o u r t s h i p d i s p l a y was In  observed i n any s p e c i e s of C e n o c o r i x a .  the mating experiments c a r r i e d out i n the c u l t u r e  t r a y s , i t was found t h a t the males c o u l d not o r i e n t t o and l o c a t e the females on t h e i r agreement song owing t o echoes from the w a l l s of the t r a y s . I n t h e s e cases the males swam v e r y f a s t i n s m a l l c i r c l e s and produced s i g n a l s which were d i f f e r e n t from "normal" c a l l i n g s i g n a l s : the p u l s e r a t e i n t h e s e s i g n a l s was more i r r e g u l a r t h a n i n the c a l l i n g and the d u r a t i o n of the s i g n a l s was  signals,  s h o r t , but the s i g n a l s  were r e p e a t e d more f r e q u e n t l y t h a n n o r m a l l y . I n s e v e r a l s p e c i e s t h e s e s i g n a l s were produced w h i l e the males were swimming ( n o r m a l l y s i g n a l s a r e o n l y produced w h i l e the specimens a r e r e s t i n g on the bottom). However, i t was  observed  t h a t the females d i d not answer t h e s e u n u s u a l c a l l s . The next female s i g n a l o c c u r r e d o n l y a f t e r the male produced a "normal" s i g n a l a g a i n . Thus t h e s e u n u s u a l male s i g n a l s are not c o u r t s h i p s i g n a l s , but s i g n a l s c r e a t e d by an u n n a t u r a l s i t u a t i o n . Males of C_. a n d e r s o n i and C. /.utahensis can produce e i t h e r a complete s i g n a l or the f i r s t p a r t of the s i g n a l a l o n e . I t was found t h a t males o f t e n respond t o the p a r t of the s i g n a l more r e a d i l y t h a n t o the complete  first signal,  w h i l e r e c e p t i v e females w i l l respond t o o n l y the complete s i g n a l s and not p a r t s of them ( T a b l e s V I I I and X ) . T h i s suggests t h a t the complete s i g n a l , w h i c h i s the c a l l i n g  song,  i s used t o a t t r a c t f e m a l e s , w h i l e the i n c o m p l e t e s i g n a l seems  175  t o hav.e the f u n c t i o n of an a g o n i s t i c s i g n a l . On the  other  hand, C_. b l a i d e l l i and C_, w i l e y a e males produce the  two  p a r t s of the s i g n a l s o f t e n i n d e p e n d e n t l y and  from each o t h e r ,  both females and males seem t o respond o n l y t o a complete  s i g n a l or o n l y t o the l a s t p a r t of the s i g n a l : the  diff-  e r e n t i a t i o n of the f u n c t i o n s of the s i g n a l s does not seem t o be c l e a r i n these two  s p e c i e s . I n the European S i g a r a  d o r s a l i s , H a s k e l l (1961) suggests t h a t one  s i g n a l could  be  a c a l l i n g song, the o t h e r a c o u r t s h i p song, but a c c o r d i n g the o b s e r v a t i o n s  i n Cenocorixa  to  t h e y f u n c t i o n as a c a l l i n g  song.and an a g o n i s t i c song. However, w o r k i n g on  Sigara  s t r i a t a , w h i c h has  s i g n a l s almost s i m i l a r t o the s i g n a l s of  S_. d o r s a l i s , F i n k e  ( 1 9 6 8 ) c o u l d not d e t e c t any d i f f e r e n c e i n  the f u n c t i o n s of the two In Cenocorixa  calls.  s t i m u l i f o r a s u c c e s s f u l c o p u l a t i o n seem  t o be i*) c a l l i n g s i g n a l of the male, and i i ) agreement 1  s i g n a l of the female. I n o r i e n t i n g t o the r e c e p t i v e female from a g r e a t d i s t a n c e , males of a l l s p e c i e s depend on a u d i t o r y s t i m u l i , but a t c l o s e range v i s u a l s t i m u l i seem t o be important  i n most s p e c i e s . However, C_. d a k o t e n s i s  seem t o o r i e n t t o v i s u a l s t i m u l i a t a l l ,  does not  but o n l y t o a u d i t -  o r y s t i m u l i . T h i s i s u n d e r s t a n d a b l e s i n c e _C. d a k o t e n s i s the o n l y s p e c i e s which was spontaneously during  is  never observed t o s t r i d u l a t e  daytime.  S c h a l l e r (1951) c l a i m s t h a t the response of females of S i g a r a s t r i a t a t o a male song i s t o swim r a p i d l y i n s m a l l c i r c l e s , and  t h u s , s i n c e the male w i l l t r y t o c o p u l a t e  with  any moving o b j e c t of s u i t a b l e s i z e , m a t i n g i s i n i t i a t e d , i . e .  176 the movement o f t h e female a t t r a c t s t h e male. However, F i n k e ( 1 9 6 8 ) , a l s o worked on S_. s t r i a t a , observed no i n c r e a s e i n s h o r t range swimming o f females i n response t o male c a l l s , but a d i f f e r e n c e i n l o n g range swimming o f t h e females was observed ("Aufschwimmen, l a n g e r e  Bewegungen im Aquarium"):  the swimming a c t i v i t y o f females i n c r e a s e d when the male s i g n a l s were payed. I t seems t o me t h a t i n b o t h cases ( S h a l ler,  1 9 5 1 ; F i n k e , 1 9 6 8 ) t h e r e a c t i o n o f t h e females o f £.  s t r i a t a was n o t a p r e m a t i n g r e s p o n s e , but an escape r e a c t i o n of u n r e c e p t i v e  females.  D u r i n g t h e p r e s e n t s t u d y i t was f r e q u e n t l y observed t h a t n o t o n l y f e m a l e s , but a l s o males o f C e n o c o r i x a would swim i n s m a l l c i r c l e s i n c u l t u r e t r a y s when s t i m u l a t e d by male s i g n a l s from specimens c l o s e b y ( o r i e n t a t i o n was imp o s s i b l e owing t o e c h o e s ) . This o f t e n a t t r a c t e d o t h e r  Corix-  i d a e and l e d t o c o p u l a t i o n attempts between two males o r males and females o f d i f f e r e n t s p e c i e s  o r even d i f f e r e n t  g e n e r a ! However, even when t h e male and female were o f t h e same s p e c i e s , t h e attempt a t c o p u l a t i o n , w i t h o u t t h e p r e c e d ing  agreement s i g n a l o f t h e female, was u n s u c c e s s f u l . I t i s r e c a l l e d t h a t i n C e n o c o r i x a t h e r e a c t i o n o f un-  r e c e p t i v e females p l a c e d w i t h caged s t r i d u l a t i n g males was for"  the""..females  t o remain m o t i o n l e s s ,  t h e males n o t being  a b l e t o g e t i n t o c l o s e p r o x i m i t y t o t h e f e m a l e s . On t h e o t h e r hand, u n r e c e p t i v e  females p l a c e d  so t h a t t h e s t r i d u l a t i n g  males c o u l d come i n t o c o n t a c t w i t h them, d i d n o t s t a y  still,  but escaped. S c h a l l e r ' s ( 1 9 5 1 ) experiments were c a r r i e d out i n g l a s s a q u a r i a and i n t h e s e I have n o t i c e d p l e n t y o f echoes,  177 as Indeed S c h a l l e r  (1951)  a l s o r e p o r t e d . Females under  such  c o n d i t i o n s would n o t be a b l e t o o r i e n t a t e away from t h e male because t h e sound would appear t o come from everywhere. I n Finke s 1  (1968)  s t u d y t h e females o f S_. s t r i a t a used were  c o l l e c t e d i n e a r l y s p r i n g , and t h e n kept i n c o n s t a n t temp e r a t u r e c a b i n e t a t 4°C u n t i l e a r l y May when t h e experiments were c a r r i e d o u t . W h i l e t h i s i s t h e time t h a t mating o c c u r s i n t h e n a t u r a l h a b i t a t , experiments w i t h C e n o c o r i x a demonstrated t h a t females kept a t 4°C would n o t a t t a i n s e x u a l m a t u r i t y . Thus t h e female specimens used by F i n k e s e x u a l l y immature, an escape  (1968)  were p r o b a b l y  and t h e swimming observed, was p r o b a b l y  reaction.  A m o r p h o l o g i c a l s t u d y o f females o f s e v e r a l  European  s p e c i e s ( c o l l e c t i o n s o f Dr. G. G. E. Scudder: C o r i x a d e n t i p e s , Sigara d o r s a l i s , A r c t o c o r i s a germari, C a l l i c o r i x a praeusta) showed t h a t a p l e c t r u m and p a r s s t r i d e n s I n p r e v i o u s s t u d i e s ( M i t i s , 1936;  existssinbthese.  S c h a l l e r , 1951;  Finke,  1968)  females a r e r e p o r t e d t o l a c k t h e s t r i d u l a t o r y a p p a r a t u s . I t i s t r u e t h a t t h i s a p p a r a t u s - i n t h e females o f t h e European s p e c i e s s t u d i e d i s l e s s developed t h a n t h e apparatus o f t h e males, and f o r i n s t a n c e t h e _S. d o r s a l i s male has about  12  rows o f w e l l developed pegs i n t h e pars s t r i d e n s , w h i l e t h e female o n l y has about seven rows o f t h e s e pegs and t h e y a r e not as s t r o n g l y t h i c k e n e d as i n t h e male. A s i m i l a r  tendency  t o have l e s s developed s t r i d u l a t o r y apparatus was found i n C e n o c o r i x a females when compared t o t t h e males \ ( c f . Table I , F i g . 4).  However, t h e r e i s no doubt t h a t t h e females o f t h e  European  species studied are able t o s t r i d u l a t e . This i s also  178  s u p p o r t e d by Southwood and L e s t o n  (1959)  who  s t a t e t h a t both  sexes of A r c t o c o r l s a g e r m a r i s t r i d u l a t e d u r i n g the b r e e d i n g season, a l t h o u g h n o t h i n g i s s a i d about how  t h i s i s connected  w i t h b r e e d i n g . F u r t h e r , d u r i n g the p r e s e n t s t u d y , s t r i d u l a t o r y s i g n a l s of both sexes of S i g a r a n e v a d e n s i s W a l l e y were r e c orded ( c f . Appendix  I I ) , and t h e i r f u n c t i o n was  observed t o  be the same as the f u n c t i o n of the s i g n a l s i n C e n o c o r i x a . Crisp  (1962)  has d e s c r i b e d the mating i n A r c t o c o r i s a  g e r m a r i and notes t h a t the male d e t e c t s the female when the l a t t e r i s swimming by. The male t h e n chases the female  and  mounts the female w h i l e the p a i r i s swimming, and t h e n the p a i r comes up tov.the s u r f a c e where c o p u l a t i o n o c c u r s . Thus the o c c u r r e n c e of c o p u l a t i o n s i n the n a t u r a l h a b i t a t s i s e a s i l y observed ( C r i s p , sequence of events was  1962).  In Cenocorixa, a s i m i l a r  f r e q u e n t l y observed, but i n t h i s  genus i t o n l y o c c u r r e d between an a c t i v e male and an unr e c p t i v e female: the p a i r came t o the s u r f a c e because of the r e l e a s e b e h a v i o r of the female. I n a s u c c e s s f u l c o p u l a t i o n i n C e n o c o r i x a the p a i r never comes up t o the s u r f a c e d u r i n g the i n i t i a t i o n of c o p u l a t i o n , but i f the c o p u l a t i o n l a s t s a l o n g t i m e , the p a i r may  o c c a s i o n a l l y come t o the s u r f a c e  t o renew i t s a i r s u p p l y . I n a few p r e v i o u s s t u d i e s on European c o r i x i d s i t had been noted t h a t the song of males does not seem t o have any v i s i b l e e f f e c t upon the females ( M i t i s , 1 9 3 6 ; L a r s e n , 1 9 3 8 ; Jansson,  1968).  However, i n a l l of these s t u d i e s both sexes  a p p a r e n t l y were kept a l l the time i n the same c o n t a i n e r , and t h u s , i f the s p e c i e s are l i k e C e n o c o r i x a s p e c i e s , most females  179 i n such c u l t u r e s would be mated i m m e d i a t e l y when t h e y become r e c e p t i v e , and most of the time the females would be u n r e c e p t ive . I n the experiments c a r r i e d out w i t h C_. b i f i d a , an i n t e r e s t i n g d i f f e r e n c e between d i f f e r e n t males was o b t a i n e d i n the' p r e s e n c e of female odor: the male kept i s o l a t e d from  all  o t h e r specimens r e a d i l y s t r i d u l a t e d i n the p r e s e n c e of female odor, but the males p i c k e d up randomly from a mixed m a l e - f e male c u l t u r e d i d not show any i n c r e a s e d s t r i d u l a t i n g  activity.  The males from the mixed c u l t u r e d i d not r e a c t t o the odor of f e m a l e s , perhaps because the e x p e r i m e n t a l s i t u a t i o n d i d not d i f f e r i n t h i s r e g a r d from the c o n d i t i o n s i n t h e i r  culture  t r a y . However, f o r the male kept i s o l a t e d from a l l o t h e r specimens, the female odor c l e a r l y was a s t i m u l u s t o s t r i d u l a t i o n (male odor d i d not have any e f f e c t ) . I n t h i s  experi-  ment o n l y one specimen was t e s t e d , but because s i m i l a r o b s e r v a t i o n s on the e f f e c t of female odor have been made on S i g a r a omani (Hungfd.) sidered  ( J a n s s o n , u n p u b l i s h e d ) , the r e s u l t s a r e con-  reliable.  The o n l y reference:, t.o pheromones i n C o r i x i d a e i s i n the s t u d y of P i n d e r and Staddon (1965  a; 1965  b ) , which shows  t h a t t r a n s - 4 - o x o h e x - 2 - e n a l i s s e c r e t e d from the m e t a t h o r a c i c g l a n d s o f both S i g a r a f a l l e n ! ( F i e b . ) and C o r i x a d e n t i p e s (Thorns.). The m e t a t h o r a c i c s t i n k g l a n d s , as w e l l as the l a r v a l d o r s a l abdominal g l a n d s have been s t u d i e d a n a t o m i c a l l y and h i s t o l o g i c a l l y i n v a r i o u s C o r i x i d a e ( B r i n d l e y ,  1929;  B e t t e n , 1943), and the f u n c t i o n of the s e c r e t i o n , l i k e  that  i n l a n d bugs (Remold, 1 9 6 2 ) , has been suggested t o be p r o t e c t i v e .  180 The  f a c t t h a t the s e c r e t i o n i s not s p e c i e s or sex  supports  t h i s concept ( P i n d e r and  Benwitz (1956) has  specific  Staddon, 1965 a ) . However,  described a d d i t i o n a l glands,  located i n  a l l t h r e e p a i r s of l e g s of C o r i x i d a e ^ the s e c r e t i o n and f u n c t i o n of which are unknown. I t i s p o s s i b l e t h a t some other pheromone occurs  in  C o r i x i d a e and a c t s as a s e x u a l a t t r a c t a n t . A l t e r n a t i v e l y , the d e f e n s i v e  s e c r e t i o h i may  under c e r t a i n c i r c u m s t a n c e s  have  a s u b s i d i a r y f u n c t i o n , namely t h a t of s e x u a l a t t r a c t i o n . However, i n C e n o c o r i x a  the method u s i n g a c o u s t i c s t i m u l i i s  v e r y e f f e c t i v e and the importance of pheromones has not been e l u c i d a t e d . On the other hand, s e v e r a l n o n - s t r i d u l a t i n g s p e c i e s of C o r i x i d a e e x i s t , and the mating b e h a v i o r  of these  species i s completely  strid-  unknown. I n these the r o l e of  u l a t i o n might be r e p l a c e d by pheromones. Butenandt has  i d e n t i f i e d trans-hex-2-enyl-acetate  ( L e p e l e t i e r and  i n Lethocerus i n d i c u s  S e r v i l l e ) , another water bug  and because t h i s c h e m i c a l  (1955)  (Belostomatidae),  i s sex s p e c i f i c , o c c u r r i n g i n males  o n l y , i t i s suggested t o f u n c t i o n as a sex a t t r a c t a n t .  181  4. E v o l u t i o n a r y s i g n i f i c a n c e of s t r i d u l a t i o n i n the genus Cenocorixa Sound p r o d u c t i o n i n i n s e c t s i s advantageous i f the sounds are produced i n c o n n e c t i o n w i t h s e x u a l b e h a v i o r  and  can guide p a i r - f o r m a t i o n ( H a s k e l l , 1 9 6 1 ) . A c o u s t i c communic a t i o n i n O r t h o p t e r a and i t s s i g n i f i c a n c e i n p a i r - f o r m a t i o n has  been d i s c u s s e d a number of times  ( c f . Alexander,  19^7;  1 9 6 8 ) . However, o n l y i n a few cases has i t been shown exp e r i m e n t a l l y t h a t the s i g n a l s a c t u a l l y f u n c t i o n as a p r e mating i s o l a t i n g mechanism so t h a t the females are a t t r a c t e d by s i g n a l s of c o n s p e c i f i c males, but do not respond t o male s i g n a l s of o t h e r s p e c i e s (Walker, k e l l , 1958; The  1957; Perdeck, 1958; Has-  1961).  b e h a v i o r a l experiments c a r r i e d out d u r i n g the  s t u d y showed t h a t both males and females of C e n o c o r i x a  present are  u s u a l l y a b l e t o d i s c r i m i n a t e the s i g n a l s o f the o p p o s i t e  sex  of c o n s p e c i f i c specimens from the s i g n a l s of a l l o t h e r s p e c i e s . By comparing the s i g n a l s of v a r i o u s s p e c i e s i t i s obvious t h a t the f r e q u e n c y  of the sound cannot have any r o l e i n the  s p e c i e s / s e x r e c o g n i t i o n . T h i s has a l s o been observed v a r i o u s o t h e r i n s e c t s ( c f . H a s k e l l , 1 9 6 1 ) . Walker suggests  in  (1957)  t h a t the key c h a r a c t e r i n s p e c i e s r e c o g n i t i o n of  t r e e c r i c k e t s ( O r t h o p t e r a , G r y l l i d a e , Oecanthinae) i s the p u l s e r a t e . However, H a s k e l l ( 1 9 6 1 ) does nof agree w i t h t h i s because i n d i v i d u a l v a r i a t i o n i n the p u l s e r a t e I s q u i t e l a r g e , and the p u l s e r a t e s of v a r i o u s s p e c i e s o f t e n o v e r l a p . H a s k e l l (1961) c l a i m s t h a t the key. c h a r a c t e r i s p u l s e modulation  (= t e m p o r a l p a t t e r n of p u l s e s i n a s i g n a l ) ,  this  182  being v e r y c o n s t a n t and s p e c i e s s p e c i f i c c h a r a c t e r i n O r t h opteran s i g n a l s . Bennet-Clark  and Ewing ( 1 9 6 9 ) , on the  other  hand, c l a i m t h a t p u l s e i n t e r v a l i s the c r i t i c a l parameter i n the c o u r t s h i p song of D r o s o p h i l a m e l a n o g a s t e r , but because the s i g n a l s of t h i s f l y are composed of p u l s e s , each of which i n c l u d e o n l y one impact,  the p u l s e i n t e r v a l c o u l d r e f e r t o p u l s e  r a t e as w e l l as to the t e m p o r a l p a t t e r n of p u l s e s . In Cenocorixa,  owing t o i n t r a s p e c i f i c v a r i a t i o n ,  the  p u l s e r a t e s of v a r i o u s s p e c i e s ( F i g s . 17-26) seem t o overl a p much more t h a n those o f t r e e c r i c k e t s (Walker,  1957),  a l t h o u g h the r e g r e s s i o n l i n e s of the s p e c i e s are more or l e s s d i f f e r e n t . However, the t e m p o r a l p a t t e r n of p u l s e s i n Cenocorixa  i s always c o n s t a n t and s p e c i e s s p e c i f i c ,  thus  s u p p o r t i n g H a s k e l l ' s (1961) concept t h i s b e i n g the key a c t e r . On the o t h e r hand, the loudness  char-  of the s i g n a l s v a r y  g r e a t l y between the s p e c i e s ( a c c o r d i n g t o s u b j e c t i v e observa t i o n s ) , and the s t r u c t u r e of p u l s e s (arrangement of  impacts  i n a p u l s e ) and the number of impacts p e r p u l s e are u s u a l l y more or l e s s s p e c i f i c ; these f a c t o r s might a l s o have an  im-  p o r t a n t r o l e i n s p e c i e s d i s c r i m i n a t i o n . A thorough s t u d y i n v o l v i n g e l e c t r o p h y s i o l o g i c a l r e c o r d i n g s i s r e q u i r e d , but o u t s i d e the aims of the p r e s e n t t h e s i s . The  was  C o r i x i d a e have  a u d i t o r y organs i n the t h o r a x (Hagemann, 1910; S c h a l l e r , 1 9 5 1 ) , but i t i s not known what d i f f i c u l t i e s would a r i s e i f r e c o r d i n g w i t h e l e c t r o d e s connected t o the nerves i s t r i e d . H a s k e l l (1961) has d i s c u s s e d whether the alone i s important  i n species r e c o g n i t i o n i n  stridulation grasshoppers,  or i f i t works t o g e t h e r w i t h some o t h e r f a c t o r or f a c t o r s .  183  Experiments  w i t h O r t h o p t e r a have demonstrated t h a t o f t e n  v i s u a l and c h e m i c a l s t i m u l i may accompany s t r i d u l a t i o n and p l a y i m p o r t a n t r o l e s i n t h e mating  behavior. I n the present  study i t was a l s o observed t h a t v i s u a l  stimulus apparently  i s i m p o r t a n t i n most s p e c i e s i n c l o s e range approach, b u t s p e c i e s d i s c r i m i n a t i o n seems t o be s o l e l y on t h e b a s i s o f the a u d i t o r y s t i m u l u s . In a d d i t i o n t o the c h a r a c t e r i s t i c s t r u c t u r e of the s t r i d u l a t o r y  d i f f e r e n c e s i n the  s i g n a l s , temporal d i f f e r e n c e s  i n t h e s t r i d u l a t i n g a c t i v i t y o f t h e s p e c i e s were a l s o observed. T h i s a g a i n i s s i m i l a r t o O r t h o p t e r a n s , w i t h some s p e c i e s s t r i d ulating  i n day time, o t h e r s a t n i g h t time ( D u m o r t i e r , 1963 c ) .  F i g . 61 summarises t h e d i e l p e r i o d i c i t y  of the s t r i d u l a t i n g  a c t i v i t y o f a l l C e n o c o r i x a s p e c i e s as i n d i c a t e d b o t h by l a b o r a t o r y experiments  and f i e l d o b s e r v a t i o n s . There i s  e v i d e n t l y a p a r t i a l temporal i s o l a t i o n i n the s t r i d u l a t i n g a c t i v i t y , and i n one p a i r o f s y m p a t r i c s p e c i e s (C.. b i f i d a C_. e x p l e t a ) t h i s d i f f e r e n c e was a l s o observed i n t h e n a t u r a l habitats. C e n o c o r i x a does n o t r e l y c o m p l e t e l y , however, on t h e s t r i d u l a t i o n behavior f o r species i s o l a t i o n , although t h i s would appear t o c o n s t i t u t e t h e main i s o l a t i n g mechanism i n sympatric s i t u a t i o n s . geographic  I t i s r e i n f o r c e d by d i f f e r e n c e s i n  d i s t r i b u t i o n and h a b i t a t p r e f e r e n c e . The s t u d y o f  the g e o g r a p h i c d i s t r i b u t i o n o f t h e s p e c i e s i n d i c a t e s some geographic  i s o l a t i o n (Figs.  54-57),  b u t owing t o t h e d i f f -  i c u l t i e s i n i d e n t i f i c a t i o n o f C e n o c o r i x a s p e c i e s ( c f . Appendix I ) , the published records c e r t a i n l y  i n c l u d e some m i s -  184  a  F i g . 6 1 . Summary of the d i e l p e r i o d i c i t y o f the s t r i d u l a t i n g a c t i v i t y of C e n o c o r i x a males. E x p l a n a t i o n s : a b s c i s s a = time of day; s t i p p l e d a r e a expresses the r e l a t i v e a c t i v i t y i n s t r i d u l a t i o n . A = C_. b i f i d a ; B = _C. k u i t e r t i ; C = C_. a n d e r s o n i ; D = _C. u t a h e n s i s ; E = C_. d a k o t e n s i s ; F = _C. b l a i s d e l l i ; G = C_. w i l e y a e ; H = C_. e x p l e t a .  184 b  24  6  12  18  24  185  i d e n t i f i c a t i o n s , and some minor m o d i f i c a t i o n s t o t h e r e c o r d e d d i s t r i b u t i o n s and range can be expected i n t h e f u t u r e . I n cases when two o r more C e n o c o r i x a s p e c i e s a r e observed s y m p a t r i c a l l y , e c o l o g i c a l d i f f e r e n c e s are u s u a l l y Scudder (1969 a; 1969 b) has r e p o r t e d a p a r t i a l  observed.  ecological  i s o l a t i o n between C_. b i f i d a and C_. expleta, s i n c e t h e y i n h a b i t d i f f e r e n t ranges  o f s a l i n i t y . T h i s i n f o r m a t i o n was c o n f i r m e d  d u r i n g t h e p r e s e n t s t u d y , b u t another p a r t i a l e c o l o g i c a l  iso-  l a t i o n between t h e two s p e c i e s was d e t e c t e d i n cases when s a l i n i t y a l l o w s t h e two t o occur i n same l a k e : C_. b i f i d a i n h a b i t s t h e v e r y edges o f t h e l a k e s i n s i d e r e e d beds, w h i l e <C. expleta. p r e f e r s s l i g h t l y deeper water o u t s i d e reed beds. P a r t i a l e c o l o g i c a l i s o l a t i o n s were a l s o d e t e c t e d between o t h e r C e n o c o r i x a p a i r s : C_. a n d e r s o n i i n permanent ponds, _C. b l a i s d e l l i i n temporary  p o o l s ; _C. k u i t e r t i i n s l o w l y r u n n i n g  or o l i g o t r o p h i c w a t e r s , C_. w i l e y a e i n s t a g n a n t , more e u t r o p h i c waters. I n Table X I I I I have c o l l e c t e d t o g e t h e r e s t i m a t e s on t h e e f f e c t i v e n e s s o f v a r i o u s i s o l a t i n g mechanisms between t h e s p e c i e s o f C e n o c o r i x a i n t h e l i g h t o f t h e p r e s e n t study. The form o f t h e t a b l e i s s i m i l a r t o t h a t o f Moore ( 1 9 ^ 9 ) f o r i s o l a t i o n o f a group o f f r o g s i n t h e n o r t h e a s t o f N o r t h However, g e o g r a p h i c  America.  i s o l a t i o n i n my t a b l e i s o n l y v e r y  r o u g h l y e s t i m a t e d because t h e d e t a i l e d d i s t r i b u t i o n s o f t h e s p e c i e s a r e unknown. E c o l o g i c a l i s o l a t i o n i s a c c o r d i n g t o my o b s e r v a t i o n s o r i s t h e p o t e n t i a l l y expected v a l u e .  Seasonal  i s o l a t i o n does not e x i s t between C e n o c o r i x a s p e c i e s , and i s always  0. Temporal i s o l a t i o n i n d i e l p e r i o d i c i t y o f t h e s t r i d -  186  u l a t i n g a c t i v i t y i s e s t i m a t e d from l a b o r a t o r y  experiments  and a c t u a l o b s e r v a t i o n s i n n a t u r a l environments; u l a t o r y i s o l a t i o n i s t a k e n d i r e c t l y from p l a y b a c k  stridexperiments  (Table X ) . From t h e Table X I I I i t can be seen t h a t t h e two s t r o n g est  i s o l a t i n g mechanisms a r e geographic  i s o l a t i o n and s t r i d -  u l a t o r y i s o l a t i o n . I n s e v e r a l cases t h e y a r e b o t h 100 p e r cent e f f e c t i v e , but i t s h o u l d be noted t h a t e s p e c i a l l y when geographic is.  i s o l a t i o n i s n o t complete,  t h e s t r i d u l a t o r y one  On t h e o j h e r hand t h e o n l y case when s t r i d u l a t o r y  iso-  l a t i o n seems t o f a i l a l t o g e t h e r , happens i n _C, w i l e y a e f e males which answer C_. d a k o t e n s i s male c a l l s every time. Howe v e r , C_. d a k o t e n s i s males do n o t answer t h e s i g n a l s o f C_. w i l e y a e females v e r y a c t i v e l y ( T a b l e I X ) , and no s e a r c h i n g b e h a v i o r was observed w i t h C_. w i l e y a e female  i n C_. d a k o t e n s i s males when s t i m u l a t e d s i g n a l s . I n a d d i t i o n , these two  s p e c i e s have a f i r m geographic  i s o l a t i o n : C_. d a k o t e n s i s  o c c u p i e s t h e n o r t h e r n p l a i n s e a s t o f t h e Rocky Mountains w h i l e _C. w i l e y a e has i t s d i s t r i b u t i o n m o s t l y between t h e Rocky Mountains and t h e Coast Range.  Table X I I I . Estimates of the magnitude of d i f f e r e n t  i s o l a t i n g mechanisms i n Cenocorixa. G =  geographic  V  isolation; E = ecological ^Males  isolation; S = stridulatory  bifida  kuit  andersoni  i s o l a t i o n ; T = temporal i s o l a t i o n i n s t r i d u l a t i o n .  utahensis  dakotensis b l a i s d e l l i  wileyae  expleta  F ema.l e s bifida  kuiterti  andersoni  utahensis  dakotensis  blaisdelli  wileyae  expleta  100 50 90 8o  G E S T  100 50 60 80  10 50 8o 60  50 100 90  ;  40  .  40  90 0 100 50  30 30 100 60  100 50 100  G E S T  100 0  100 0  0 0  100 0  100 0  0 0  100 100  80  0  0  10  0  40  10  G E S T  100 0 100 80  100 0 100 ^0  100 0 100 10  50 75 100 ~0  100  G E S T  50 0 100 60  60 0 100 30  100 0 100 10  50  G E S T  _  100 0  0-  95 0  0-  100 0 100 10  20 0 100 90  100 0 100 0  100 0 100 10  0 100 10  G E S T  100 0 100 50  100 0  -  0  60 75 100 0  100 0 100 0  100 0 80 30  G E S T  90 0 100 70  95 50 90 30  100 0 100 30  10 0 90 0  100 0 0 50  100 0 100  G E S T  0 30 100 50  100 100 100 0  100 100 100 0  10 90 100 0  30 90 8o 30  100 100 90  x  .  100 0 100 0  40  0  50-  '  100 100 100 10  •  60 90 100 0  0  40-  60 90 100  100  0  100 50  0  100 100 8o  100  0 _  20  0  95 70 60 - 20  40  95 70 100 20  I  188  5. E v o l u t i o n and  s t r i d u l a t i o n i n Corixidae  I n g e n e r a l i n e v o l u t i o n i t i s the more c o m p l i c a t e d forms t h a t a r e the most advanced ones (Rensch, 1 9 5 9 ) • I f t h i s concept i s a p p l i e d t o the s t r u c t u r e of the  stridulatory  s i g n a l s of C e n o c o r i x a males, an o r d e r can be o b t a i n e d  as  shown i n F i g . 62. C e r t a i n l y the genus can be d i v i d e d i n t o two  subgroups a c c o r d i n g t o the s t r u c t u r e of male s i g n a l s :  1) S i g n a l s composed of an u n i n t e r r u p t e d sequence of p u l s e s ; the b i f i d a group (£.  b i f i d a , _C.. k u i t e r t i ,  C. a n d e r s o n i , C_.  u t a h e n s i s , and C.. d a k o t e n s i s ) and 2) S i g n a l s composed of d i s t i n c t l y s e p a r a t e groups of p u l s e s ; the w i l e y a e group (C!. b l a i s d e l l i , _C. w i l e y a e , and _C. e x p l e t a ) . T h i s subd i v i s i o n of the genus c o i n c i d e s w i t h a d i v i s i o n t h a t e x i s t s i n m o r p h o l o g i c a l c h a r a c t e r s . The w i l e y a e group i n body form i s more s l e n d e r t h a n the b i f i d a group, and the r i g h t paramere of the male g e n i t a l i a i n the l a t t e r group i s b i f u r c a t e  (except  i n _C. a n d e r s o n i ) , w h i l e i n the w i l e y a e group i t i s not b i f u r c a t e . I n _C. a n d e r s o n i the n o n - b i f u r c a t e form of the p a r a mere might be a secondary m o d i f i c a t i o n . The g e n e r a l g e o g r a p h i c suggests  a western  d i s t r i b u t i o n of the genus  o r i g i n i n areas south of the P l e i s t o c e n e  g l a c i a t i o n . However, the e v o l u t i o n c o u l d have been pre  or  p o s t P l e i s t o c e n e or p a r t l y both. I f more d e t a i l e d s p e c u l a t i o n of e v o l u t i o n of the genus i s d e s i r e d , my on zoogeography, morphology, and would be as  s u g g e s t i o n , based  stridulation differences,  follows:  The a n c e s t o r s of the genus were something l i k e day C_. b i f i d a . A t some time t h i s a n c e s t r a l form was  present split  189  a  b  t  i  mil lllll  l  1111  l  1111  i  OOUlGMIIMi!  s  h  F i g . 62. Diagram of suggested i n c r e a s i n g c o m p l e x i t y .of s i g n a l s of C e n o c o r i x a males. The s i m p l i e s t type i s a t the t o p . a = _C. b i f i d a ; b = _C. k u i t e r t i ; c = C, a n d e r s o n i ; d - _C. u t a h e n s i s ; e = C_. d a k o t e n s i s ; f = _C. b l a i s d e l l i ; g = _C. w i l e y a e ; h = _C. e x p l e t a . E x p l a n a t i o n s : i n each s i g n a l one bar r e p r e s e n t s one p u l s e ; w i d t h of the bar i n d i c a t e s r e l a t i v e d u r a t i o n of the p u l s e , h e i g h t of the bar r e l a t i v e loudness of the p u l s e . P u l s e arrangement shows the t e m p o r a l p a t t e r n of the s i g n a l s . In some s p e c i e s f i r s t p a r t o f the s i g n a l can be produced a l o n e and i n these two s e p a r a t e s i g n a l s a r e i n d i c a t e d (b, c, and d ) .  199  i n t o two:  b i f i d a group and w i l e y a e group. The  b i f i d a group  m i g r a t e d i n d i f f e r e n t d i r e c t o n s : i ) Northwards i n the weste r n s i d e of the Rocky Mountines,  g i v i n g r i s e t o _C. b i f i d a i n  the i n t e r i o r p l a t e a u ; i i ) Northwards i n the e a s t e r n s.ide of the Rocky Mountines:  _C. d a k o t e n s i s ; i i i ) Southwest t o the  h i g h areas on mountains: C. k u i t e r t i ; i v ) Northwest t o the P a c i f i c W e s t c o a s t : C_. a n d e r s o n i ; v) Eastwards over the Rocky Mountains:  _C. u t a h e n s i s . Meanwhile, the w i l e y a e group gave  r i s e t o C. b l a i s d e l l i a f t e r c r o s s i n g the Coast Range t o the P a c i f i c Coast i n south, and C_. e x p l e t a a f t e r m i g r a t i n g over the Rocky M o u n t a i n s . . T h i s i n F i g . 63,  h y p o t h e t i c a l e v o l u t i o n i s summarised  and p r e s e n t day geographic  d i s t r i b u t i o n can  be  d e r i v e d from the h y p o t h e s i s by a l l o w i n g £. b i f i d a t o c r o s s over the Rocky Mountains somewhere i n Wyoming - Idaho t o the n o r t h e r n p l a i n s , and _C. u t a h e n s i s and _C. e x p l e t a the o t h e r way  back t o the i n t e r i o r : p l a t e a u between the Rocky Mountains  and the Coast Range. The  f u n c t i o n o f the Rocky Mountains as an  b a r r i e r i s suggested  isolating  by o b s e r v a t i o n s on geographic  variation  i n the s i g n a l s of C_. b i f i d a ( J a n s s o n , t o be p u b l i s h e d ) : A s l i g h t d i f f e r e n c e was  d e t e c t e d between the p o p u l a t i o n s of  B r i t i s h Columbia and A l b e r t a , and the p o p u l a t i o n i n n o r t h e r n Utah possesses  an i n t e r m e d i a t e s i g n a l compared t o the n o r t h e r n  p o p u l a t i o n s . A l s o some s l i g h t m o r p h o l o g i c a l d i f f e r e n c e s b e t ween these p o p u l a t i o n s were d e t e c t e d ( c f . Appendix I ) .  These  o b s e r v a t i o n s do not a f f e c t the r e s u l t s of the p r e s e n t  study,  but show t h a t the two n o r t h e r n p o p u l a t i o n s c o u l d e v o l v e a p a r t i f the apparent ..connection t h r o u g h Wyoming - Idaho breaks.  19.1  F i g . 63. Suggested e v o l u t i o n of C e n o c o r i x a s p e c i e s . Based on g e o g r a p h i c d i s t r i b u t i o n , g e n e r a l morphology, and s t r i d u l a t i o n . 1 = C. b i f i d a ; 2 = C_. d a k o t e n s i s ; 3 = C_. k u i t e r t i ; 4" = _C. a n d e r s o n i ; 5 = C. u t a h e n s i s ; 6 = _C. w i l e y a e ; 7 = C.. b l a i s d e l l i ; 8 = _C. e x p l e t a . •  192  D i v e r g e n c e i n the a n i m a l kingdom i s thought t o t a k e p l a c e by g e o g r a p h i c i s o l a t i o n and e v o l u t i o n of e f f e c t i v e i s o l a t i n g mechanisms (Mayr, 1 9 6 3 ) . Premating  isolating  mechanisms a r e u s u a l l y c o n s i d e r e d the most e f f e c t i v e because t h e y p r e v e n t waste of the s e x u a l p r o d u c t s . Thus, premating i s o l a t i n g mechanisms, not s u r p r i s i n g l y , a r e the  predominant  i s o l a t i n g mechanisms between c l o s e l y r e l a t e d s p e c i e s t h a t occur s y m p a t r i c a l l y ( e . g . B l a i r , 1955; Brown, 1965; Hagen, 1967; L i c h t , 1969; L i l e y , 1966; S p i e t h , 1947; Wasserman, 1 9 5 7 ) . I n i n s e c t s which produce are  sound, a c o u s t i c  signals  suggested t o be one of the commonest p r e m a t i n g  iso-  l a t i n g mechanisms ( e . g . A l e x a n d e r , 19^7; 1968; A l e x a n d e r and Moore, 1962; B e n n e t - C l a r k and Ewing, 1969; H a s k e l l ,  I96I;  Perdeck, 1958; Roth and Hartman, 1967; Spooner, 1964; 1968; Van T a s s e l , 1965; Waldon, 1964; Walker, 1 9 5 7 ) . E v o l u t i o n of such sound based p r e m a t i n g  isolating  mechanism i s an i n t e r e s t i n g problem, and A l e x a n d e r ( 1 9 6 2 ) suggests t h a t i n O r t h o p t e r a , the f i r s t c r i c k e t a p p a r e n t l y was  a l r e a d y a s p e c i a l i z e d s t r i d u l a t o r . He f u r t h e r  suggests  t h a t the f u n c t i o n of s t r i d u l a t i o n i n a n c i e n t c r i c k e t s  was  l i n k e d w i t h c o u r t s h i p b e h a v i o r , and t h a t the o t h e r f u n c t i o n s of  s t r i d u l a t i o n i n l i v i n g c r i c k e t s have e v o l v e d from t h i s  c o u r t s h i p song. A c c o r d i n g t o A l e x a n d e r ( 1 9 6 2 ) t h i s is  concept  s u p p o r t e d by the f a c t t h a t c o u r t s h i p i n c r i c k e t s t h a t have  l o s t the a b i l i t y t o s t r i d u l a t e , i n c l u d e s l i f t i n g  of the wings.  Wing l i f t i n g a s s o c i a t e d w i t h c o u r t s h i p i s observed i n B l a t t a ria  ( R o t h and W i l l i s , 1952; Roth and Hartman, 1 9 6 7 ) , and i s  e v i d e n t l y a p r i m i t i v e behavior i n Orthopteroids (Alexander,  193  1 9 6 4 ) , and thus i n t h i s t a x o n t h e r e i s a good b a s i s f o r t h e e v o l u t i o n o f sound p r o d u c t i o n as an a d d i t i o n t o these wing l i f t i n g movements. The f u n c t i o n o f t h e i n i t i a l c o u r t s h i p was r e s t r i c t e d t o s h o r t d i s t a n c e a t t r a c t i o n , and i n O r t h o p t e r a , when a t t r a c t i o n from l o n g e r d i s t a n c e s e v o l v e d , t h i s c o u r t s h i p song gave r i s e t o a c a l l i n g song, and when a c o u s t i c a l b e h a v i o r became more c o m p l i c a t e d , o t h e r c a t e g o r i e s o f songs e v o l v e d from t h e s e p r e - e x i s t i n g ones ( A l e x a n d e r , 1 9 6 2 ) . V a r i o u s s t r i d u l a t o r y mechanisms e x i s t i n both t r i a l and a q u a t i c Hemiptera,  terres-  but these mechanisms a r e f a r  too d i f f e r e n t t o have had a common o r i g i n . A q u a t i c Hemiptera a r e s e c o n d a r i l y adapted t o a q u a t i c environment, and t h e r e is  some evidence t h a t t h e y a l l descended from a common a n -  c e s t o r ( C h i n a , 1 9 5 5 ) . However, i n a q u a t i c Hemiptera,  there  a r e a g a i n s e v e r a l s t r i d u l a t o r y mechanisms ( D u m o r t i e r , 1963 a ) , and s i n c e these a r e q u i t e d i f f e r e n t , i t i s apparent s t r i d u l a t i o n i n these a q u a t i c bugs has e v o l v e d  that  independently  s e v e r a l times. The six  family Corixidae i s taxonomically subdivided into  s u b f a m i l i e s . I t i s n o t known i f any s t r i d u l a t o r y appar-  a t u s o r song e x i s t  i n t h e s u b f a m i l i e s D i a p r e p o c o r i n a e and  S t e n o c o r i n a e . The Cymatiinae  (genus Cymatia) do n o t seem t o  have any s t r i d u l a t o r y organ, and no sounds have been r e c o r d e d . European M i c r o n e c t i n a e (genus M i c r o n e c t a ) a r e known t o s t r i d u l a t e ( M i t i s , 1936; Southwood and L e s t o n , 1 9 5 9 ) , and t h e mechanism i s p r o b a b l y by use o f t h e abdominal s t r i g i l  (Mitis,  1 9 3 6 ) . However, A m e r i c a n M i c r o n e c t i n a e (genus Tenagobia) a r e s a i d t o l a c k t h i s abdominal s t r i g i l  (Hungerford,  1948). In  194  the H e t e r o c o r i x i n a e according  records  on s t r i d u l a t i o n are l a c k i n g , but  t o the drawings i n Hungerford ( 1 9 4 8 ) a l l s p e c i e s  have a w e l l developed abdominal s t r i g i l i n males, and  spec-  i a l i s e d pegs are l o c a t e d a t the p o s t e r i o r edge of the  fifth  abdominal te.rgum j u s t a n t e r i o r t o the s t r i g i l : i t i s p o s s i b l e t h a t s t r i d u l a t o r y s i g n a l s are produced w i t h t h i s a p p a r a t u s , and  thus u t i l i s e an apparatus s i m i l a r t o t h a t i n the European  Micronectinae. C o r i x i n a e seems t o be the o n l y s u b f a m i l y p o s s e s s i n g  a  s t r i d u l a t o r y mechanism t h a t i n v o l v e s s t r i d u l a t o r y pegs of the f r o n t femora and  the m a x i l l a r y p l a t e . However,  strid-  u l a t i o n i s not u n i v e r s a l i n C o r i x i n a e : s e v e r a l genera of t h i s subfamily  are not a b l e t o s t r i d u l a t e , and  known whether t h e y r e p r e s e n t  i t i s not  an advanced group t h a t has  lost  the s t r i d u l a t o r y a p p a r a t u s , or a p r i m i t i v e group t h a t have not e v o l v e d  i t . The  existence  of v a r i o u s d i f f e r e n t s t r i d -  u l a t o r y mechanisms i n C o r i x i d a e , n e v e r t h e l e s s ,  suggest t h a t  s t r i d u l a t i o n i s not a p l e s i o m o r p h i c  but r a t h e r  apomorphic one  (Hennig,;. 1 9 6 6 ) , one  s e p a r a t i o n of the s u b f a m i l i e s . The  character, t h a t has  evolved  after  n o n - s t r i d u l a t i n g genera  of C o r i x i n a e are thus p o s t u l a t e d never t o have had ulatiry  an  a  strid-  ability.  S i n c e C o r i x i n a e do not have a d i s t i n c t c o u r t s h i p d i s p l a y , i t i s not l i k e l y t h a t the s t r i d u l a t o r y b e h a v i o r has i n the way  evolved  suggested i n O r t h o p t e r a by A l e x a n d e r ( 1 9 6 2 ) .  a l t e r n a t i v e e v o l u t i o n must be suggested, and  An  ritualization  of "comfort" movements seems t o be a p o s s i b i l i t y . r i t u a l i z a t i o n i s w e l l documented i n v e r t e b r a t e s  Such  (e.g.  Huxley,  195  1 9 1 4 ) , but seems t o be a p o s s i b i l i t y i n i n v e r t e b r a t e s as w e l l : waving d i s p l a y of f i d d l e r crabs  (genus Uca)  (Crane,  1966).  I n the C o r i x i n a e , each p a i r of l e g s has been adapted t o serve a d i f f e r e n t p r i m a r y f u n c t i o n : the f o r e l e g s f o r f e e d i n g , the m i d d l e l e g s f o r c l i n g i n g , and the h i n d for  legs  swimming. However, these l e g s a l s o have i m p o r t a n t  sub-  sidiary functions. I t w i l l be r e c a l l e d t h a t the v a r i o u s s p e c i e s of Cenoc o r i x a w i l l f r e q u e n t l y r u b / t h e h i n d l e g s a l o n g the c o s t a l m a r g i n of the h e m i e l y t r a . T h i s movement, w h i c h was  often  observed a f t e r the i n s e c t s had been h a n d l e d , u n d o u b t e d l y i s aimed a t r e a r r a n g i n g the l a t e r a l abdominal h a i r s t h a t are v e r y i m p o r t a n t  i n maintaining  the a i r bubble between  the wings and the abdominal dorsum f o r r e s p i r a t i o n (Popham, I960; P a r s o n s , 1 9 7 0 ) - W h i l e t h i s i s c l e a r l y a "comfort" movement, i t i s a l s o a movement t h a t produces sounds w h i c h have been i n t e r p r e t e d by some a u t h o r s as s t r i d u l a t i o n (Moore, I 9 6 I ; Finke, 1968). In Cenocorixa  i t was  shown t h a t such sounds  do indeed have c e r t a i n c h a r a c t e r i s t i c s t h a t are r e q u i r e d i n a s t r i d u l a t o r y signal:,; but a l l s p e c i e s were observed t o produce a comparable sound. A t p r e s e n t  t h e y do not seem t o  serve as s t r i d u l a t o r y s i g n a l s i n C e n o c o r i x a .  However, t r u e  s t r i d u l a t o r y s i g n a l s c o u l d e a s i l y e v o l v e from t h i s . S i m i l a r l y , the f r o n t l e g s , a l t h o u g h modified  used".and h i g h l y  f o r f e e d i n g , a l s o are used i n c l e a n i n g movements,  e s p e c i a l l y movements a c r o s s the l a b i u m f o r " p r e e n i n g " l o n g s e n s o r y setae t h a t are l o c a t e d a t i t s t i p (Lo and  the Acton,  196  1 9 6 9 ) . Such movements couild w e l l have been t h e p r e c u r s o r o f the p r e s e n t  day s t r i d u l a t o r y movements i n C e n o c o r i x a and  other s t r i d u l a t i n g C o r i x i n a e . Any  two p a r t s o f an e x o s c e l e t o n can be rubbed  together  t o produce a n o i s e , and so these movements c o u l d e a s i l y have become r i t u a l i s e d and t h e p a r t s m o d i f i e d . A n o t h e r m o d i f i c a t i o n i n t h e t h o r a c i c t r a c h e a l system c o u l d have l e d t o t h e e v o l u t i o n o f t h e sound r e c e i v i n g tympanum. I n a s i m i l a r manner, movements o f t h e s c l e r o t i z e d p a r t s of t h e abdomen d u r i n g d e f a c a t i o n or mating or both c o u l d produce sounds which - l i k e w i s e c o u l d have been s e l e c t e d i n European M i c r o n e c t i n a e . A p a r a l l e l e v o l u t i o n i s a l s o suggested i n Heterocorixinae. I t was n o t e d i n Cenocorixa. t h a t i n most s p e c i e s  there  i s o n l y a s i n g l e type o f s i g n a l i n each sex. I n c o n t r a s t t o t h i s , t h e O r t h o p t e r a have f r e q u e n t l y s e v e r a l d i f f e r e n t  types  of song t h a t appear t o be s p e c i a l i s e d f o r p r e c i s e f u n c t i o n s . Thus, i n O r t h o p t e r a  t h e r e a r e d i s t i n c t and d i f f e r e n t  calling,  c o u r t s h i p , r i v a l ' s , e t c . songs. In Cenocorixa  t h e v a r i o u s experiments u n d e r t a k e n suggest  t h a t i n some s p e c i e s (_C. b i f i d a , C_. d a k o t e n s i s , _C. e x p l e t a ) the same s i g n a l can f u n c t i o n as a c a l l i n g song and a g o n i s t i c song. I n some o t h e r s p e c i e s (_C. b l a i s d e l l i , _C. w i l e y a e )  part  of t h e i r "normal" s i g n a l can be produced s e p a r a t e l y , but no o b v i o u s f u n c t i o n o f t h i s p a r t c o u l d be d e t e c t e d . F u r t h e r , i n two  s p e c i e s (_C. a n d e r s o n i  and _C. u t a h e n s i s ) p a r t o f t h e i r  "normal" c a l l seemed t o have a d i f f e r e n t f u n c t i o n ( a g o n i s t i c song) from t h a t o f t h e "normal" c a l l ( c a l l i n g  song).  I t would appear t h a t here we have e v i d e n c e o f t h e i n c i p i e n t e v o l u t i o n o f s t r i d u l a t o r y d i v e r s i t y towards a more complex a c o u s t i c a l signals  communication system. A g o n i s t i c  seem t o be e v o l v i n g from a c a l l i n g s i g n a l , i.-.e.  a double s t r i d u l a t o r y s i g n a l i s e v o l v i n g from a s i n g l e pre-existing  one. The C o r i x i n a e , and i n p a r t i c u l a r t h e  genus C e n o c o r i x a , can be c o n s i d e r e d on t h e e v o l u t i o n a r y threshold,of  stridulatory diversification.  198 V. SUMMARY 1. uce  I n t h e genus C e n o c o r i x a both males and females p r o d -  s p e c i e s and sex s p e c i f i c s t r i d u l a t o r y s i g n a l s : t h e sound  i s produced by r u b b i n g s p e c i a l i z e d s t r i d u l a t o r y pegs, anterobasally the  on t h e f r o n t femora ( p a r s s t r i d e n s ) ,  edge o f t h e m a x i l l a r y p l a t e  located  against  (plectrum). A c o r r e l a t i o n  seems t o e x i s t between t h e l o u d n e s s o f s i g n a l s and morphology of t h e s t r i d u l a t o r y a p p a r a t u s . 2. S p e c i f i c d i f f e r e n c e s temporal p a t t e r n and  of p u l s e s , pulse r a t e , s t r u c t u r e  signal length.  of pulses,  Change i n temperature a f f e c t s t h e p u l s e  r a t e and, when a p p l i c a b l e , but  i n t h e s i g n a l s were found i n t h e  t h e p u l s e group r e p e t i t i o n r a t e ,  not u s u a l l y t h e t e m p o r a l p a t t e r n  of pulses.  3 . A n n u a l rhythm o f s t r i d u l a t i o n i s c o r r e l a t e d  with  s e x u a l m a t u r i t y . I n males spontaneous s t r i d u l a t i o n commences when mature sperm o c c u r s i n t h e t e s t e s : i n t h e s p r i n g , summer, and i n l a t e f a l l .  early  I n areas where no f r e e z e - u p e x i s t s ,  the males s t r i d u l a t e throughout t h e w i n t e r . I n females spontaneous s t r i d u l a t i o n was never observed, b u t i n d u c e d  strid-  u l a t i o n commences when c h o r i o n a t e d eggs a r e found i n t h e l a t e r a l o v i d u c t s and a p p a r e n t l y no sperm e x i s t s i n t h e r e c e p t aculum s e m i n i s . S e x u a l m a t u r i t y i n females i s o n l y reached i n ifehelspring and e a r l y summer. 4. B e h a v i o r a l l y function  t h e s t r i d u l a t i o n o f males seems t o  both as a c a l l i n g s i g n a l and as an a g o n i s t i c  s i g n a l . The  "female s i g n a l can be c l a s s i f i e d as an agreement s i g n a l f o r i t i s o n l y produced by r e c e p t i v e ulatory  females and a f t e r a s t r i d -  s t i m u l u s from t h e male. R e c e n t l y mated females do  199 not s t r i d u l a t e and do not a c c e p t males a t t e m p t i n g 5. I n most s p e c i e s  copulation.  t h e males answer almost any s t r i d -  u l a t o r y s t i m u l i , but o n l y the s i g n a l s o f c o n s p e c i f i c i n i t i a t e searching  females  b e h a v i o r i n the males. Females do not  respond t o male s i g n a l s o f o t h e r s p e c i e s ,  but t h e response  t o c o n s p e c i f i c male s i g n a l s i s t o s t a y s t a t i o n a r y and answer by s t r i d u l a t i n g . 6. S t r i d u l a t i o n f u n c t i o n s mechanism i n the genus s t u d i e d ,  a,s a p r e m a t i n g i s o l a t i n g but does n o t . c o n s t i t u t e  the  whole i s o l a t i n g mechanism. I t i s r e i n f o r c e d by g e o g r a p h i c , and  e c o l o g i c a l i s o l a t i o n i n a number of c a s e s . 7.  I t i s suggested t h a t t h e s t r i d u l a t o r y movements i n  Corixidae  have a r i s e n by r i t u a l i z a t i o n o f comfort movements.  8. The C o r i x i d a e  a r e c o n s i d e r e d t o r e p r e s e n t a stage i n  e v o l u t i o n a t which d i v e r s i f i c a t i o n o f s t r i d u l a t o r y s i g n a l s i s evolving  from a s i n g l e p r e - e x i s t i n g one. A t the p r e s e n t  t i m e , most s p e c i e s i n a t l e a s t two  have a s i n g l e male c a l l t h a t can f u n c t i o n  contexts.  200  VI.  LITERATURE CITED  A l e x a n d e r , R.D. 1962. E v o l u t i o n a r y change i n c r i c k e t a c o u s t i c a l communication. S y s t . Z o o l . 1 1 : 53-72,/ - " - 1964. The e v o l u t i o n of m a t i n g b e h a v i o u r i n A r t h r o p o d s . Symp. R. e n t . Soc. Lond. 2: 78-94. - " - 1967- A c o u s t i c a l communication Ent.  12:  i n a r t h r o p o d s . A.  Rev.  495-526.  - " - 1968. A r t h r o p o d s . ( I n ) Sebeok, T.A. ( e d . ) : A n i m a l communication. Techniques of s t u d y and r e s u l t s of r e s e a r c h : 167-216. I n d i a n a Univ. P r e s s , Bloomington, London. A l e x a n d e r , R.D. and Moore, T.E. 1962. The e v o l u t i o n a r y r e l a t i o n s h i p s of 1 7 - y e a r and 1 3 - y e a r c i c a d a s , and t h r e e new s p e c i e s (Homoptera, C i c a d i d a e , M a g i c i c a d a ) . M i s c . P u b l . Mus. Z o o l . Univ. M i c h i g a n 1 2 1 : 1-59. A n d r i e u , A . J . 1963. Techniques used f o r the p h y s i c a l s t u d y of a c o u s t i c s i g n a l s of a n i m a l o r i g i n . ( I n ) B u s n e l , R.-G. ( e d . ) : A c o u s t i c b e h a v i o u r of a n i m a l s : 25-47. E l s e v i e r P u b l . Co., Amsterdam - London - New York. B a l l , R. 1846. On n o i s e s produced by one o f the N o t o n e c t i d a e . Rep. B r i t . Assoc. Adv. S c i . 1846: 64-65. B e n n e t - C l a r k , H.C. and Ewing, A.W. 1969. P u l s e i n t e r v a l as a c r i t i c a l parameter i n the c o u r t s h i p song of D r o s o p h i l a m e l a n o g a s t e r . Anim. Behav. 17: 755-759B e n w i t z , G. 1956. Die B e i n d r u s e n der C o r i x i d e n . Z o o l . Jb. (Anat.) 75: 379-382. B e t t e n , H. 1 9 ^ 3 . Die S t i n k d r u s e n der C o r i x i d e n . Z o o l . Jb. (Anat.) 68: 137-175B l a i r , W.F. 1955- D i f f e r e n t i a t i o n of mating c a l l i n spadef o o t s , genus Scaphiopus. Texas. J . S c i . 7: 1 8 3 - I 0 8 . B r i n d l e y , M.D.H. 1929. On the r e p u g n a t o r i a l g l a n d s of C o r i x a . Trans, ent. Soc. Lond. 77: 7-13B r o o k s , A.R. and K e l t o n , L.A. 1967. A q u a t i c and s e m i a q u a t i c H e t e r o p t e r a of A l b e r t a , Saskatchewan, and Manitoba ( H e m i p t e r a ) . Mem. ent. Soc. Canada 5 1 : 1-92. Brown, R.G.B. 1965. C o u r t s h i p b e h a v i o u r i n the D r o s o p h i l a o b s c u r a group. P a r t I I . Comparative studies'! B e h a v i o r 25: 281-323-  201  B u s n e l , R.-G. 1963- On c e r t a i n a s p e c t s of a n i m a l a c o u s t i c s i g n a l s . ( I n ) B u s n e l , R.-G. ( e d . ) : A c o u s t i c behaviour of a n i m a l s : 6 9 - 1 1 1 . E l s e v i e r P u b l . Co., Amsterdam-London - New York. Butenandt, A. 1955- A c t i v e substances i n the i n s e c t kingdom. Nova A c t a L e o p o l d i n a (Deutsche Akad. Nat.) 17: 445-471. C a r p e n t e r , G.H. 3:  1894. The s t r i d u l a t i o n of C o r i x a . I r . Nat.  253-255.  C h i n a , W.E. 1955- The e v o l u t i o n of the water bugs. Symp. on o r g a n i c e v o l u t i o n . B u l l . Nat. I n s t . S c i . I n d i a 7: 91-103. Crane, J . 1966. Combat, d i s p l a y and r i t u a l i z a t i o n i n f i d d l e r crabs (Ocypodinae, genus Uca). P h i l . Trans. R. Soc. Ser. B 251:  459-472.  C r i s p , D.T. 1962. O b s e r v a t i o n s on the b i o l o g y of C o r i x a g e r m a r i ( F i e b . ) (Hemiptera, H e t e r o p t e r a ) i n an u p l a n d r e s e r v o i r . A r c h . H y d r o b i o l . 58: 261-280. Davey, K.G. 1958. The m i g r a t i o n of spermatozoa I n the female of Rhodnius p r o l i x u s S t a h l . J . Exp. B i o l . 35: 694-701. D e l c o , E.A., J r . i 9 6 0 . Sound d i s c r i m i n a t i o n by males of two c y p r i n i d f i s h e s . Texas J . S c i . 12: 48-54. D i l g e r , W.C. 1956. H o s t i l e b e h a v i o r and r e p r o d u c t i v e i s o - l a t i n g mechanisms i n the A v i a n genera Catharus and H y l o c i c h l a . AUK 73: 313-353. D u m o r t i e r , B. 1963 a. Morphology of sound e m i s s i o n apparatus i n A r t h r o p o d a . ( I n ) B u s n e l , R.-G. ( e d . ) : A c o u s t i c b e h a v i o u r of a n i m a l s : 277-345. E l s e v i e r P u b l . Co., Amsterdam - London - New York. - " - 1963 b. The p h y s i c a l c h a r a c t e r i s t i c s of sound e m i s s i o n . I b i d : 346-373. ^ " - 1963 c. E t h o l o g i c a l and p h y s i o l o g i c a l s t u d y of sound e m i s s i o n s i n A r t h r o p o d a . I b i d : 583-654. Edmondson, W.T. 1966. P a c i f i c Coast and Great B a s i n . ( I n ) F r e y , D.G. ( e d . ) : Limnology i n N o r t h A m e r i c a : 371-392. Univ. Wisconsin Press. Ewen, A.B. 1962. An improvedaaldehyde f u c h s i n s t a i n i n g technique f o r neurosecretory products i n i n s e c t s . Trans, Am. M i c r o s c . Soc. 8 l : 9^-96.  202  F i n k e , C. 1968. LautMusserung und V e r h a l t e n von S i g a r a s t r i a t a und C a l l i c o r i x a praeusta. ( C o r i x i d a e Leach., H y d r o c o r i sae L a t r . ) . Z. v e r g l . P h y s i o l . 58: 398-422. Geer, B.W. 1967. D i e t a r y c h o l i n e r e q u i r e m e n t s f o r sperm m o t i l i t y and normal mating a c t i v i t y i n D r o s o p h i l a m e l a n o g a s t e r . B i o l . B u l l . 133: 5 4 8 - 5 6 6 . Geer, B.W. and Newburgh R.W. 1970. C a r n i t i n e a c e t y l t r a n s f e r a s e and spermatozoan development i n D r o s o p h i l a m e l a n o g a s t e r . J . B i o l . Chem. 245: 71—79. Hagemahn, J . 1910. B e i t r & g e z u r K e n n t n i s von C o r i x a . Z o o l . Jb. (Anat.) 30: 373-426. Hagen, D.W. 1967. I s o l a t i n g mechanimsm i n the t h r e e s p i n e s t i c k l e b a c k s ( G a s t e r o s t e u s ) . J . F i s h . Res. Bd. Canada 24:  1637-1692.  H a s k e l l , P.T. 1957- S t r i d u l a t i o n and i t s a n a l y s i s i n c e r t a i n G e o c o r i s a e (Hemiptera H e t e r o p t e r a ) . P r o c . Z o o l . Soc. Lond. 129: 351-358. - " - 1958. S t r i d u l a t i o n and a s s o c i a t e d b e h a v i o u r i n c e r t a i n O r t h o p t e r a , 2. S t r i d u l a t i o n of f e m a l e s , and t h e i r beh a v i o u r w i t h males. Br. J . Anim. Behav. 6: 27-42. - " - i 9 6 0 . S t r i d u l a t i o n and a s s o c i a t e d b e h a v i o u r O r t h o p t e r a , 3. The  i n certain  i n f l u e n c e of gonads. I b i d , 8:  76-81.  - " - I 9 6 I . I n s e c t sounds. 189 pp. Whitney L t d . , London. - " - 1964. Sound p r o d u c t i o n . ( I n ) R o c k s t e i n , M. ( e d . ) : The p h y s i o l o g y of I n s e c t a , I : 563-608. H e n n i g j . W. 1966. P h y l o g e n e t i c s y s t e m a t i c s . 263 pp. Univ. I l l i n o i s P r e s s , Urbana. H u n g e r f o r d , H.B. 1948. The C o r i x i d a e of the Western Hemisphere. Univ. Kansas S c i . B u l l . 32: I-827. - " - 1956. A new C e n o c o r i x a from the n o r t h w e s t e r n U n i t e d S t a t e s (Hemiptera - C o r i x i d a e ) . J . Kansas, ent. Soc. 29:  39-^1.  H u x l e y , J.S. 1914. The c o u r t s h i p - h a b i t s of the g r e a t c r e s t e d grebe ( P o d i c e p s c r i s t a t u s ) ; w i t h an a d d i t i o n t o the t h e o r y of s e x u a l s e l e c t i o n . P r o c . z o o l . Soc. Lond. 35: 491-562.  Jansson, A. 1968. D i e l p e r i o d i c i t y of the s t r i d u l a t i n g a c t i v i t y of C a l l i c o r i x a p r o d u c t a R e u t e r ( H e t e r o p t e r a , C o r i x i d a e ) . Ann. Z o o l . F e n n i c i 5: 265-269.  203  Jansson, A. 1969. I d e n t i f i c a t i o n o f l a r v a l C o r i x i d a e (Heter o p t e r a ) o f N o r t h e r n Europe. Ann. Z o o l . F e n h i c i 6: 2 8 9 312.  Johansson, A.S. 195^. R e l a t i o n o f n u t r i t i o n t o e n d o c r i n e - r e p r o d u c t i v e f u n c t i o n s i n t h e milkweed bug Oncopeltus f a s c i a t u s (Dallas) (Heteroptera: Lygaeidae). N y t t Mag. Z o o l . 7: 1-132. - " - 1964. F e e d i n g and n u t r i t i o n i n r e p r o d u c t i v e p r o c e s s i n i n s e c t s . ( I n ) Highnam, K.C. ( e d . ) : I n s e c t r e p r o d u c t i o n . Symp. No. 2, R. e n t . Soc. Lond., 43-55. K i r k a l d y , G.W. 1 9 0 1 . The s t r i d u l a t i o n o f C o r i x a . ( R h y n c o t a ) . E n t o m o l o g i s t 3 4 : 9Lansbury, I . 1955- D i s t r i b u t i o n a l r e c o r d s o f N o r t h American C o r i x i d a e , (Hemiptera: H e t e r o p t e r a ) . Can. Ent. 8 7 : 4 7 4 481.  - " - i 9 6 0 . The C o r i x i d a e ( H e m i p t e r a - H e t e r o p t e r a ) o f B r i t i s h Columbia. P r o c . ent. Soc. B r i t i s h Columbia 57: 34-43. L a r s e n , 0. 1938. Untersuchungen uber den G e s c h l e c h t s a p p a r a t der a q u a t i l e n Wanzen. Opusc. Ent. S u p p l . I , 388 pp. Lee, H.T.-Y. 1950. A p r e l i m i n a r y h i s t o l o g i c a l s t u d y o f t h e insemination reaction i n Drosophila gibberosa. B i o l . B u l l . 9 8 : 25-33. L e s t o n , D. 1955- M i s c e l l a n e o u s b i o l o g i c a l notes on B r i t i s h C o r i x i d a e and N o t o n e c t i d a e (Hem.). E n t o m o l o g i s t ' s mon. Mag. 9 1 : 9 2 - 9 5 .  L e s t o n , D. and P r i n g l e , J.W.S. 1963. A c o u s t i c a l b e h a v i o u r of Hemiptera. ( I n ) B u s n e l , R.-G.:(ed.): A c o u s t i c b e h a v i o u r o f a n i m a l s : 391-411. E l s e v i e r P u b l . Co., Amsterdam - London - New York. L i c h t , L.E. 1969. Comparative b r e e d i n g b e h a v i o r o f t h e r e d l e g g e d f r o g (Rana a u r o r a a u r o r a ) and t h e w e s t e r n s p o t t e d f r o g (Rana p r e t i o s a p r e t i o s a ) i n s o u t h w e s t e r n B r i t i s h Columbia. Can. J . Z o o l . 47: I 2 8 7 - I 2 9 9 . L i l e y , N.R. 1966. E t h o l o g i c a l i s o l a t i n g mechanisms, i n f o u r sympatric species of p o e c i l i i d f i s h e s . Behaviour, S u p p l . 1, 197 pp. L i t t l e John, M.J. and Michaud, T.C. 1959- M a t i n g c a l l d i s c r i m i n a t i o n by females o f S t r e c k e r ' s chorus :fr:qg ( P s e u d a c r i s s t r e c k e r i ) . Texas J . S c i . 1 1 : 86-92.  204  Lo,  S.E. and A c t o n , A.B. 1 9 6 9 . The u l t r a s t r u c t u r e o f t h e r o s t r a l s e n s o r y organs o f t h e water bug, C e n o c o r i x a b i f i d a (Hungerford) (Hemiptera). Can. J . Z o o l . 4 7 : 717-722.  M a r l e r , P. 1957- S p e c i f i c d i s t i n c t i v e n e s s i n t h e communic a t i o n s i g n a l s of b i r d s . Behaviour 11: 13-39Mayr, E. 1 9 6 3 . A n i m a l s p e c i e s and e v o l u t i o n . 797 PP- Oxford U n i v . Press,,London. M i t i s , H. von. 1 9 3 6 . Zur B i o l o g i e d e r C o r i x i d e n , Z. Morph. Okol. T i e r e 3 0 : 4 7 9 - 4 9 5 .  Stridulation.  Moore, J.A. 1 9 4 9 . P a t t e r n s o f e v o l u t i o n i n t h e genus Rana. ( I n ) Jepsen, G.L., Mayr, E., and Simpson, G.G. ( e d s . ) : G e n e t i c s , p a l e o n t o l o g y , and e v o l u t i o n : 3 1 5 - 3 3 8 . P r i n c e t o n , New J e r s e y . Moore, T.E. 1 9 6 1 . A u d i o s p e c t r o g r a p h i c a n a l y s i s o f sounds of Hemiptera and Homoptera. Ann. e n t . Soc. Am. 5 4 : 273-291.  Pajunen, V . I . 1 9 7 0 . Phenology o f a r r e s t o f o v a r i a n matura t i o n i n rock, p o o l c o r i x i d s ( H e t e r o p t e r a , C o r i x i d a e ) . Ann. Z o o l . F e n n i c i J: 2 7 0 - 2 7 2 . Pajunen, V . I . and J a n s s o n , A. 1 9 6 9 . D i s p e r s a l , o f t h e r o c k p o o l c o r i x i d s A r c t o c o r j s a c a r i n a t a ( S a h i b . ) and C a l l i c o r i x a p r o d u c t a (ReutT) ( H e t e r o p t e r a , C o r i x i d a e ) . I b i d , 6: 391-427. P a r s o n s , M.C. 1 9 6 5 . C l y p e a l m o d i f i c a t i o n s i n some l i t t o r a l and a q u a t i c H e t e r o p t e r a . Can. J . Z o o l . 4 3 : 1 6 1 - 1 6 6 . -  " - 1 9 6 6 . L a b i a l s k e l e t o n and m u s c u l a t u r e o f t h e Hydroc o r i s a e ( H e t e r o p t e r a ) . Can. J . Z o o l . 4 4 : 1 0 5 1 - 1 0 8 4 .  -  " - 1 9 7 0 . R e s p i r a t o r y s i g n i f i c a n c e o f t h e t h o r a c i c and abdominal morphology o f t h e t h r e e a q u a t i c bugs Ambrysus, N o t o n e c t a , and H e s p e r o c o r i x a ( I n s e c t a , H e t e r o p t e r a ) . Z. Morph. 6kol. T i e r e 6 6 : 2 4 2 - 2 9 8 .  P a t t e r s o n , J.T. 1 9 4 6 . A new type o f I s o l a t i n g mechanism. P r o c . Nat. Acad. S c i . 3 2 : 2 0 2 - 2 0 8 . P a t t e r s o n , J.T. and Stone, W.S. 1 9 5 2 . E v o l u t i o n i n t h e genus D r o s o p h i l a . 610 pp. M a c m i l l a n Co., New York. Perdeck, A.C. 1 9 5 8 . The i s o l a t i n g v a l u e o f s p e c i f i c song p a t t e r n s i n two s i b l i n g s p e c i e s o f g r a s s h o p p e r s ( C h o r t h i p p u s brunneus Thunb. and C_. b i g u t t u l u s L. ). Behaviour 12: 1-75.  205  P i n d e r , A.R. and Staddon, B.W. 1965 a. Trans-4-oxohex-2e n a l i n the o d i f e r o u s s e c r e t i o n of S i g a r a f a l l e n i (Fieb.) (Hemiptera-Heteroptera). N a t u r e , Lond. 205: 106-107.  - " - 1965 b. The o d i f e r o u s s e c r e t i o n of the water bug S i g a r a f a l l e n i ( F i e b . ) . J . Chem. Soc. 530: 2955-2958. Popham, E . J . i 9 6 0 . On the r e s p i r a t i o n of a q u a t i c Hemiptera H e t e r o p t e r a w i t h s p e c i a l r e f e r e n c e t o the C o r i x i d a e . Proc. Z o o l . Soc. Lond. 135: 209-242. - " - I 9 6 I . The f u n c t i o n of the p a l e a l pegs of C o r i x i d a e (Hemiptera H e t e r o p t e r a ) . N a t u r e , Lond. 190: 742-743. Rawson, D.S. and Moore, J.E. 1944. The s a l i n e l a k e s Saskatchewan. Can. J . Res. (D) 22: 141-201.  of  Remold, H. 1962. Uber d i e b i o l o g i s c h e bedeutung der D u f t d r u s e n b e i den Landwanzen ( G e o c o r i s a e ) . Z. v e r g l . P h y s i o l . 45: 636-694. Rensch, B. 1959- E v o l u t i o n above the s p e c i e s l e v e l . 419 Methuen and Co.,Ltd., London. -  pp.  R i c h a r d s , O.W. 1961. The s o c i a l i n s e c t s . 219 pp. Harper B r o t h e r s , New York.  and  Roth, L.M. and Hartman, H.B. 1967. Sound p r o d u c t i o n and i t s e v o l u t i o n a r y s i g n i f i c a n c e i n the B l a t t a r i a . Ann. Ent. Soc. Amer. 60: 740-752. Roth, L.M. and W i l l i s , E.R. 1952. A s t u d y of c o c k r o a c h b e h a v i o r . Am. M i d i . Nat. 47: 66-129. S c h a l l e r , F. 1951- Lauterzeugung und HftrvermGgen von C o r i x a ( C a l l i c o r i x a ) s t r i a t a L. Z: v e r g l . P h y s i o l . 33: 476-486. Scudder, G.G.E. 1964. Wing muscle polymorphism i n Am. Z o o l . 4: 331-332.  Cenocorixa.  - " - 1966. The Immature stages of C e n o c o r i x a b i f i d a (Hung.) and C_. expleta;' ( U h l e r ) (Hemiptera: C o r i x i d a e ) . J . ent. Soc. B r i t i s h Columbia 63: 33-40. - " - 1969 a. The d i s t r i b u t i o n of two s p e c i e s of C e n o c o r i x a i n i n l a n d s a l i n e l a k e s of B r i t i s h Columbia. I b i d , 66:  32-41  - " - 1969 b. The fauna of s a l i n e l a k e s on the F r a s e r P l a t e a u i n B r i t i s h Columbia. Verh. I n t e r n a t . V e r e i n . L i m n o l . 17: 430-439.  206  Scudder, G.G.E. 1971. Comparative morphology of i n s e c t g e n i t a l i a . A. Rev. Ent. 16: ( i n p r e s s ) . S i e g e l , S. 1956. Nonparametric s t a t i s t i c s f o r the b e h a v i o r a l s c i e n c e s . 312 pp. M c G r a w - H i l l Co., New York. Southwood, T.R.E. and L e s t o n , D. 1959. Land and water bugs of the B r i t i s h I s l e s . 436 pp. F r . Warne and Co., London. Sparrow, R.A.H. 1966. Comparative l i m n o l o g y of l a k e s i n the s o u t h e r n Rocky M o u n t a i n t r e n c h , B r i t i s h Columbia. J . F i s h . Res. Bd.. Canada 23: 1 8 7 5 - I 8 9 5 . S p i e t h , H.T. 19^7. S e x u a l b e h a v i o u r and i s o l a t i o n i n Drosop h i l a . I . The m a t i n g b e h a v i o u r of s p e c i e s of w i l l i s t o n i group. E v o l u t i o n 1: 17-31. Spooner, J.D. 1964. The Texas bush katydaid - i t s sound t h e i r s i g n i f i c a n c e . Anim. Behav. 12: 235-244.  and  - " - 1968. P a i r - f o r m i n g a c o u s t i c systems of p h a n e r o p t e r i n e k a t y d i d s ( O r t h o p t e r a , T e t t i g o n i i d a e ) . Anim. Behav. 16: 197-212.  S t r i c k b e r g e r , M.W. 1962. E x p e r i m e n t s i n g e n e t i c s w i t h D r o s o p h i l a . 144 pp. J . W i l e y and Sons, New York. 1  Thomson, M. Van  1894.  Stridulation  of C o r i x a . I r . Nat.  3: 114-115.  T a s s e l , E.R. 1965. An a u d i o s p e c t r o g r a p h i c study on s t r i d u l a t i o n as an i s o l a t i n g mechanism i n the genus Berosus ( C o l e o p t e r a , H y d r o p h i l i d a e ) . Ann. ent. Soc. Am.  50:  407-413.  Waldon, I . 1964. C o u r t s h i p sound p r o d u c t i o n i n two s y m p a t r i c s i b l i n g D r o s o p h i l a s p e c i e s . S c i e n c e 144: 191-193. Walker, T.J. 1957- S p e c i f i t y i n the response of female t r e e c r i c k e t s ( O r t h o p t e r a , G r y l l i d a e , Oecanthinae) t o c a l l i n g songs of the males. Ann. Ent. Soc. Am. 50: 626-636. - " - 1962. F a c t o r s r e s p o n s i b l e f o r i n t r a s p e c i f i c v a r i a t i o n i n the c a l l i n g songs of c r i c k e t s . E v o l u t i o n 16: 407-428. Wasserman, A.O. 1957. F a c t o r s a f f e c t i n g i n t e r b r e e d i n g i n symp a t r i c s p e c i e s of s p a d e f o o t s (genus S c a p h i o b u s ) . Evol u t i o n 11: 320-338. Young, E.C. 1965. F l i g h t muscle polymorphism i n B r i t i s h C o r i x i d a e : E c o l o g i c a l o b s e r v a t i o n s . J . Anim. E c o l . 34: 353-390. Zwart, K.W.R. 1965. On the i n f l u e n c e o f some food substances on s u r v i v a l of C o r i x i d a e . ( H e t e r o p t e r a ) . X I I I n t . Congr. Ent., London: 411-412.  207  APPENDIX I SYSTEMATIC NOTES AND NEW SYNONYMY IN THE GENUS CENOCORIXA Hungerford (1948) i n h i s r e v i s i o n o f t h e C o r i x i d a e o f the w e s t e r n hemisphere, e r e c t e d a new genus C e n o c o r i x a i n which he p l a c e d n i n e s p e c i e s . Subsequently,  Hungerford  (1956)  d e s c r i b e d a new s p e c i e s and more r e c e n t l y , Lansbury ( i 9 6 0 ) has d e s c r i b e d t h r e e a d d i t i o n a l s p e c i e s i n t h e genus. A t t h e present time, Cenocorixa  thus c o n t a i n s 13 d e s c r i b e d s p e c i e s .  In t h e p r e s e n t study i t was d i s c o v e r e d t h a t t h e r e a r e only eight d i s t i n c t  s p e c i e s i n t h e genus; s e v e r a l o f t h e  p r e v i o u s l y d e s c r i b e d s p e c i e s must be r e l e g a t e d t o synonymy. In a d d i t i o n , w h i l e t h e p u b l i s h e d d e s c r i p t i o n s o f t h e s p e c i e s are i n g e n e r a l adequate, t h e p u b l i s h e d f i g u r e s on s p e c i f i c d i f f e r e n c e s a r e n o t v e r y a c c u r a t e and t h e key i n Hungerford (1948) i s somewhat u n r e l i a b l e , s i n c e t h e c h a r a c t e r s u t i l i s e d are o f t e n r a t h e r v a r i a b l e . T h i s Appendix thus r e v i s e s t h e v a l i d  species, gives  the new synonymy, and p r e s e n t s a r e v i s e d key t o males o f the genus. A key t o females o f t h e genus i s i n p r e p a r a t i o n .  C e n o c o r i x a b i f i d a . (Hungerford) A r c t o c o r i x a b i f i d a Hungerford 1926, Can. Ent. 5 8 : 268.  C e n o c o r i x a b i f i d a , Hungerford 1948, Univ. Kansas S c i . B u l l . 3 2 : 569; r e d . e s c r i p t i o n . SYN.  NOV. C e n o c o r i x a  h u n g e r f o r d i Lansbury i 9 6 0 , Proc. e n t .  Soc. B. C. 5 7 : 3 6 . C e n o c o r i x a b i f i d a , B r o o k s and K e l t o n 1967, Mem. E n t .  208  Soc. Canada 5 1 : 24; r e d i s c r i p t i o n . C o n s i d e r a b l e g e o g r a p h i c and i n t r a s p e c i f i c v a r i a t i o n was observed i n t h i s s p e c i e s . The d e s c r i p t i o n o f t h e s p e c i e s by Hungerford ( 1 9 4 8 ) must be ammended as f o l l o w s : The peg row o f t h e male p a l a i s c l e a r l y broken i n specimens from A l b e r t a (as s t a t e d by H u n g e r f o r d , 1 9 4 8 ) , but i n specimens from n o r t h e r n Utah i t i s not so c l e a r l y broken, and i t i s u s u a l l y unbroken i n specimens from B r i t i s h Columbia (Fig. 68). The r i g h t paramere i s n o t q u i t e as i n t h e drawing i n H u n g e r f o r d ( 1 9 4 8 ) , and t h e shape o f t h e more p r o x i m a l p r o j e c t i o n v a r i e s from r o u n d i s h i n A l b e r t a and Utah t o sharp i n B r i t i s h Columbia specimens  specimens  ( F i g s . 71 and 7 2 ) :  a l s o t h e shape o f t h e s t r i g i l v a r i e s s l i g h t l y . D o r s a l v i e w of t h e p o s t e r i o r abdominal t e r g a i s shown i n F i g . 6 4 . Lansbury ( i 9 6 0 ) d e s c r i b e d t h i s s p e c i e s under t h e name C_. h u n g e r f o r d i from B r i t i s h Columbia, but a p p a r e n t l y he was not aware o f t h e e x i s t i n g v a r i a t i o n . I have c r o s s mated specimens from A l b e r t a and B r i t i s h Columbia ( t o be p u b l i s h e d ) and d e s p i t e t h e d i f f e r e n c e s between t h e p o p u l a t i o n s , t h e experiment showed t h a t c r o s s b r e e d i n g was s u c c e s s f u l ( a t t h e moment t h e c u l t u r e s a r e i n t h e F^ g e n e r a t i o n ) . Typo m a t e r i a . l i e x a m i n e d : H o l o t y p e cf, a l l o t y p e $, and l a * ( p a r a t y p e ) : :Lost Lake, A l b e r t a , Canada, (the p a r a t y p e male s t u d i e d belongs t o C_. u t a h e n s i s ) [Univ. K a n s a s ] . 4 cfcf and 8 ?$ o f C_. h u n g e r f o r d i Lansb., Kaml o o p s , B r i t i s h Columbia  [U.B.C.].  A d d i t i o n a l m a t e r i a l : Canada, B r i t i s h Columbia,  Chilcotin,  209  Beeche's P r a i r i e - ; Kamloops, Lac du B o i s a r e a (LB2); A l b e r t a , Brooks. USA:  Utah, Wasatch Co.,  Cenocorixa k u i t e r t i  Strawberry R e s e r v o i r .  Hungerford  C e n o c o r i x a k u i t e r t i Hungerford 1948, Univ. Kansas Sci. Bull.  32:;:571.  The tergum of the middle l o b e of the seventh  abdominal  segment d o r s a l l y does not have a d i s t i n c t t u f t of h a i r s as shown i n Hungerford  ( 1 9 4 8 ) , but o n l y a few s h o r t h a i r s  appear ( F i g . 6 4 ) . The arrangement of the p a l a r pegs i s shown i n F i g . 69, and some v a r i a t i o n of the shape of the r i g h t paramere i n Fig.  73.  M a t e r i a l examined: USA:  C a l i f o r n i a , Tuolumne Co.,  Tioga  Pass ( t y p e l o c a l i t y ) .  Cenocorixa andersoni  Hungerford  Cenocorixa, a n d e r s o n i Hungerford 1948, Univ. Kansas S c i . B u l l . 32, 573. ^ZE*  2°J£* C e n o c o r i x a m a l k i n i Hungerford 1956, J . Kansas ent. Soc. 29:  SYN.. NOV.  C e n o c o r i x a downesi Lansbury i 9 6 0 , P r o c . ent. Soc. B. C. 57:  The  39.  40.  o r i g i n a l d e s c r i p t i o n of Hungerford  ( 1 9 4 8 ) must be  am-  mended as f o l l o w s : Male abdomen d o r s a l l y has the median l o b e of the tergum 7 more or l e s s d i s t i n c t l y s e p a r a t e d from the l e f t l o b e by a break, which i s sometimes c l e a r l y seen, but may  a l s o be almost  210  n o n - e x i s t i n g . However, the two l o b e s are " t i e d "  together  w i t h a t u f t of h a i r s o r i g i n a t i n g from the l e f t l o b e ; s p e c i e s thus has  two h a i r t u f t s , a c a u d a l l o n g i t u d i a l  a t r a n s v e r s e o n e . ( F i g . 6 5 ) . The i s somewhat v a r i a b l e and  and  s i z e of the t r a n s v e r s e  tuft  the s i z e of the break between the  l o b e s } i s p r o p o r t i o n a l t o the s i z e of the The  the  tuft.  l a s t segment of the h i n d l e g ( t a r s u s 2) i s some-  times dark brown, but sometimes the whole l e g i s l i g h t brown. Arrangement of the pegs of p a l a i s shown i n F i g . 69, and  some i n t r a s p e c i f i c v a r i a t i o n of the r i g h t paramere i s  shown i n F i g s . 71 and  73.  H u n g e r f o r d (1956) d e s c r i b e d t h i s s p e c i e s under the name C_. m a l k i n i a p p a r e n t l y because he had not n o t i c e d  the  v a r i a t i o n i n the c o l o r of the t a r s u s 2; the specimens  on  w h i c h the o r i g i n a l C.. a n d e r s o n i  d e s c r i p t i o n was  based,  do  not have a dark brown t a r s u s 2, w h i l e a l l C_. m a l k i n i type specimens I have seen, have dark brown t a r s u s 2. However, the c o l o r of the t a r s u s 2 seems t o depend on the c o l o r of the bottom of the pond or l a k e : i n l a k e s w i t h dark bottom t a r s u s 2 i s dark brown, but i n p a l e bottom l a k e s i t i s l i g h t * . Lansbury ( i 9 6 0 ) based h i s d e s c r i p t i o n of C_. downesi on  only  one male specimen. He n o t i c e d the e x i s t e n c e of the t r a n s v e r s e h a i r t u f t , but because the t i p of the median l o b e of tergum V I I i s broken o f f , the specimen does not have  any  * For the e f f e c t of c o l o r of the bottom of l a k e s on C o r i x i d a e , see: Popham, E.J. 1941. The v a r i a t i o n i h c o l o u r of c e r t a i n s p e c i e s of A r c t o c o r i s a (Hemiptera, C o r i x i d a e ) and i t s s i g n i f i c a n c e . Proc. Z o o l . Soc. Lond. I l l ( A ) : 135-172.  211  c a u d a l h a i r t u f t : Lansbury ( i 9 6 0 ) e v i d e n t l y d i d not n o t i c e t h a t the specimen was Type m a t e r i a l  broken.  examined:  H o l o t y p e cf , 1 ? ( p a r a t y p e ) : Washington, Kalama R i v e r ; 1 cf ( p a r a t y p e ) : Oregon, F l o r e n c e  [Univ. K a n s a s ] . _C. m a l k i n i :  H o l o t y p e cf, a l l o t y p e ?, 7 oV and 1 ? ( p a r a t y p e s ) : Chase Lake, Snohomish Co.  Washington,  [Univ. Kansas, and C a l i f .  S c i ] . 1 cf ( p a r a t y p e ) : Oregon, F l o r e n c e  Acad.  [Mnivs-Kansas ].  downesi: h o l o t y p e cf: B r i t i s h Columbia, Vancouver. A d d i t i o n a l m a t e r i a l : Canada: B r i t i s h Columbia, Spect a c l e Lake, Vancouver  I s l a n d [ C a l i f . Acad. S c i . , c o l l . J .  Simpson]; Vancouver, S t a n l e y Park; White Rock, r o a d s i d e pond; Abbotsford,  Trout H a t c h e r y pond ( c o l l .  i n g t o n , Whatcom Co.,  J . Ryan). USA:  Wash-  Custer.  Cenocorixa utahensis  (Hungerford)  A r c t o c o r i x a u t a h e n s i s Hungerford 1925, B u l l . B r o o k l y n Ent. Soc. 20: 22. C e n o c o r i x a u t a h e n s i s , Hungerford 1948, U n i v . Kansas S c i B u l l . 32: 58O; r e d e s c r i p t i o n . C e n o c o r i x a u t a h e n s i s , -Brooks.and K e l t o n 1967,  Mem.  Ent. Soc. Canada 5 1 : 25; ' red.e.script!on,V, The m a t e r i a l s t u d i e d agreed w i t h the d i s c r i p t i o n i n Hung e r f o r d ( 1 9 4 8 ) . However, the drawing on the r i g h t paramere i n H u n g e r f o r d ( 1 9 4 8 ) i s s l i g h t l y m i s l e a d i n g , and v a r i a t i o n i n the shape of t h i s i s shown i n F i g s . 71 and 74. D o r s a l v i e w of p o s t e r i o r abdominal t e r g a i s shown i n F i g . 6 5 , and arrangement  of the p a l a r pegs i n F i g . 69.  212  Type m a t e r i a l  examined:  H o l o t y p e cf, a l l o t y p e $, 2 cfcf 3 $$ Emery Co.,  [Univ.  (paratypes):  Utah,  Kansas].  A d d i t i o n a l m a t e r i a l : Canada, A l b e r t a , G l e i c h e n ; M e d i c i n e Hat.  USA:  W a s h i n g t o n , F r a n k l i n Co.,  Co.,  Kootenay R e s e r v o i r ;  Co.,  Starvation  Hatch; Duchesne  Reservoir;  Arctocorixa Ent.  60:  (Hungerford)  d a k o t e n s i s Hungerford 1928,  Kansas S c i . B u l l .  Ent.  material  Soc.  Hungerford 1948,  32: 567;  Cenocorixa dakotensis, Mem.  Can.  229.  Cenocorixa dakotensis,  gerford  Mesa; F r a n k l i n  Utah, G a r f i e l d Co.,  Cenocorixa dakotensis  The  Brooks;  red.escription.  Brooks and  Canada 51:  Univ.  Kelton  1967,  23; ' r e d e s c r i p t i o n ; , ;  s t u d i e d agreed w i t h the d e s c r i p t i o n i n Hun-  ( 1 9 4 8 ) , except t h a t some v a r i a t i o n i n the shape of  the r i g h t paramere was  observed, and  i s shown i n F i g s . 71  and  74. D o r s a l view of p o s t e r i o r abdominal t e r g a i n male i s shown i n F i g . 66, and  arrangement of p a l a r pegs i n F i g .  Material studied: Medicine  Canada, A l b e r t a , G l e i c h e ;  69. Brooks;  Hat.  Cenocorixa b l a i s d e l l i Arctocorixa Ent.  7:  Sigara 23:  (Hungerford)  b l a i s d e l l i Hungerford 1930,  Pan-Pacif.  26.  b l a i s d e l l i , J a c z e w s k i 1931,  511.  Arch.  Hydrobiol.  213 C e n o c o r i x a b l a i s d e l l i , Hungerford  19^8, Univ.  Kansas S c i . B u l l . 3 2 : 57^; r e d e s c r i p t i o n . SYN.  NOV.  C e n o c o r i x a c o l u m b i e n s i s Lansbury i 9 6 0 ,  Proc.  ent. Soc. B. C. 57: 3 8 . Hungerfordis  (19^8) d e s c r i p t i o n s h o u l d be ammended t o •  s t a t e t h a t t h e seventh abdominal tergum o f males has t h r e e c a u d a l p r o j e c t i o n s ( F i g . 6 6 ) ; t h e r i g h t paramere i s as shown i n F i g s . 71 and 'Jk. Arrangement o f p a l a r pegs i s shown i n F i g . 70. Lansbury ( i 9 6 0 ) d e s c r i b e d t h i s  s p e c i e s from B r i t i s h  Columbia under t h e name C_. c o l u m b i e n s i s . He a l s o gave drawi n g s , which, however, do n o t agree w i t h h i s type specimens. He a p p a r e n t l y d i d n o t r e c o g n i s e t h e specimens as C_. b l a i s delli  (Hungfd.),  because Hungerford  o n l y from C a l i f o r n i a . reference t o Jaczewski  (19^8) r e c o r d s t h e l a t t e r  However, Hungerford (1931),  (1948) g i v e s a  and i n t h e l a t t e r t h e s p e c i e s  i s r e c o r d e d from Washington. A p p a r e n t l y t h e s p e c i e s  occurs  a l l a l o n g t h e c o a s t from B r i t i s h Columbia t o C a l i f o r n i a , a l t h o u g h no r e c o r d from Oregon has been p u b l i s h e d . Specimens from B r i t i s h Columbia and C a l i f o r n i a geographic  do n o t show any apparent  variation.  Type m a t e r i a l examined: 3  cfcf  (paratypes): Vine H i l l ,  Contra Costa Co.,  [Univ. K a n s a s ] ; 2 rfc? 1 $ ( p a r a t y p e s ) : B e r k e l e y ,  California  California  [ C a l i f . Acad. S c i . ] (one o f t h e male p a r a t y p e s has a female Corisella  d e c o l o r ( U h l e r ) mounted on t h e same p i n ) . C_. c o l -  umbiensis  Lansb. : h o l o t y p e  cf,  a l l o t y p e ?, 5  cftf  5 ?? ( p a r a -  t y p e s ) : Pond, Univ. B r i t . C o l . , B r i t i s h Columbia  [U.B.C.].  214 A d d i t i o n a l m a t e r i a l : Canada, B r i t i s h Columbia, S t a n l e y Park; U.B.C. a r e a . USA: San F r a n c i s c o ; Humboldt Co.,  Vancouver,  C a l i f o r n i a , San Mateo  Co.,  Calm Beach.  C e n o c o r i x a w i l e y a e (Hungerford) A r c t o c o r i x a w i l e y a e Hungerford 1 9 2 6 , 58:  Can. Ent.  271.  C e n o c o r i x a w i l e y a e , Hungerford 19^8, S c i . B u l l . 32:  578;  Univ.  redescription.  The shape of the r i g h t paramere i s as i n F i g s . 71 75?  Kansas  and  and not as shown i n H u n g e r f o r d ( 1 9 4 8 ) . D o r s a l v i e w o f  p o s t e r i o r abdominal t e r g a of male i s shown i n F i g . 6 7 , arrangement  of p a l a r pegs i n F i g . 7 0 .  M a t e r i a l s t u d i e d : USA:  Washigton, F r a n k l i n Co.,  l i v a n dam a r e a ; Oregon, Sherman Co., Kent; Deschutes  0'SulCo.,  La P i n e ; C a l i f o r n i a , Modoc Co., N e w e l l ; L a s s e n Co., S a i d Lake; D o y l e ; A l p i n e Co., M o n i t o r Pass; Mono Co. and Tuolumne Co., T i o g a Pass; Mono Co., B l a c k Lake; Nevada, Nye Co., V a l l e y ; Utah, G a r f i e l d Co., Hatch; Duchesne Co., Res.; Wasatch Co.,  Railroad  Starvation  S t r a w b e r r y Res.,  Cenocorixa expleta (Uhler) Corisa expleta Uhler 1895,  ( i n ) G i l l e t t e , C.  P.  and Baker, C. F.: Hemiptera of C o l o r a d o , Colorado Agr. Exp. S t . B u l l . 3 1 ,  Tech. s e r . 1:  A r c t o c o r i s a e x p l e t a , K i r k a l d y and 1909,  P r o c . Ent. Soc. Wash. 1 0 :  63.  Torre-Bueno 195.  C e n o c o r i x a e x p l e t a , Hungerford 19^8,  Univ. Kansas  215  S c i . B u l l . 32: 576;  redescription.  C e n o c o r i x a e x p l e t a , Brooks and K e l t o n 1967, Ent. Soc. Canada 5 1 : 24;  Mem.  redescription.  No major d i f f e r e n c e s were d e t e c t e d between the r e d e s c r i p t i o n of Hungerford v a r i a t i o n was  ( 1 9 4 8 ) and the m a t e r i a l s t u d i e d . S l i g h t  observed  i n the shape of the r i g h t paramere  ( F i g s . 71 and 7 5 ) - D o r s a l v i e w of male abdomen i s shown i n F i g . 67 and male p a l a i s shown i n F i g . 70. M a t e r i a l s t u d i e d : Canada, B r i t i s h Columbia, Kamloops a r e a (LB2); Okanagan V a l l e y , F a l k l a n d . USA, Grant Co.,  Soap Lake.  S i g a r a nevadensis  (Walley)  Argtocorixa.'nevadeHsls 68:  SYN.  NOV.  >S^S/S«.  ******  Washington,  W a l l e y 1936, Can.  Ent.  58.  Sigara (Vermicorixa) nevadensis,  Hungerford  Univ. Kansas S c i . B u l l . 32: 704;  redescription.  Cenocorixa  s o r e n s o n i Hungerford  1948,  1948,  Univ.  Kansas S c i . B u l l . 32: 565. I n a d d i t i o n t o the C e n o c o r i x a s p e c i e s above,  Hungerford  ( 1 9 4 8 ) d e s c r i b e d C_. s o r e n s o n i i n h i s monograph:f r.om m a t e r i a l c o l l e c t e d from Brigham, Utah. However, i n the g e n e r a l - d e s c r i p t i o n of the genus C e n o c o r i x a , Hungerford  ( 1 9 4 8 ) was  forced  t o make an e x c e p t i o n i n C_. s o r e n s o n i females: the l a s t v e n t r a l abdominal segment i s i n c i s e d a t t i p i n a l l o t h e r s p e c i e s . I n a d d i t i o n , C_. s o r e n s o n i appears t o be c l e a r l y s m a l l e r t h a n o t h e r s p e c i e s of the genus, and the median l o n g i t u d i n a l c a r i n a of the pronotum i s v e r y s h o r t . A l s o the c l a v a l p a t t e r n i s  216  d i f f e r e n t from o t h e r C e n o c o r i x a  s p e c i e s : i n C_. s o r e n s o n i t h e  t r a n s v e r s e p a l e l i n e s a r e enlargened  i n the middle of the  clavus w h i l e i n a l l other species the l i n e s are v e r m i c u l a t e , but n o t enlargened.  A l s o t h e male p a l a i n C_. s o r e n s o n i has  a ridge i n the middle, Cenocorixa  which does n o t appear i n any o t h e r  s p e c i e s . A l l these  " e x c e p t i o n s " would p l a c e C_.  s o r e n s o n i i n t h e genus S i g a r a . Indeed t h e s p e c i e s i s p l a c e d i n t h i s genus i n Hungerford (1948) under t h e name S_. nevadensis, although  the o r i g i n a l d e s c r i p t i o n placed i t i n the  genus A r c t o c o r i x a ( W a l l e y , 1 9 3 6 ) . " . The  d e s c r i p t i o n s and f i g u r e s o f S_. n e v a d e n s i s and.  C_. s o r e n s o n i i n H u n g e r f o r d ( 1 9 4 8 ) a r e v e r y s i m i l a r and no a d d i t i o n a l d e s c r i p t i o n or f i g u r e i s needed. Some i n t r a s p e c i f i c v a r i a t i o n was found i n t h e shape o f t h e r i g h t paramere: the t h i c k n e s s o f t h e d i s t a l p r o j e c t i o n v a r i e s s l i g h t l y . Type m a t e r i a l examined: H o l o t y p e  cf,  a l l o t y p e ?, 4  cfcf j  ?? ( p a r a t y p e s ) : Humboldt R i v e r , Nevada [Am. Mus. Nat. H i s t . ] , 1 cf l $ ( p a r a t y p e s ) : as above [Univ. Kansas]. holotype  cf, a l l o t y p e $, 5 ^  [Univ. K a n s a s ] ,  C_. s o r e n s o n i :  ( p a r a t y p e s ) : Utah, Brigham  2 cfcf 2 ?? ( p a r a t y p e s ) : as above [Utah  State  Univ.]. A d d i t i o n a l m a t e r i a l : Utah, Box E l d e r Co., Bear R i v e r .  I d e n t i f i c a t i o n of Cenocorixa  s p e c i e s i s d i f f i c u l t and  some p r a c t i c e i s needed f o r c o r r e c t r e s u l t s . I n males t h e i d e n t i f i c a t i o n has t o be based m o s t l y  on t h e s t r u c t u r e o f t h e  abdominal dorsum ( 7 t h segment), and t h e shape o f t h e r i g h t paramere. Females a r e more d i f f i c u l t , and no s u i t a b l e key  217  i s a v a i l a b l e so f a r . A key f o r the males i s as f o l l o w s : 1 ( 2 ) Pal'a w i t h the peg  row  s h a r p l y curved  ( F i g . 70 b ) . . . . _C.  wileyae  2 ( 1 ) P a l a w i t h the peg row not s h a r p l y curved 3 (4)  3  P a l a w i t h s p i n o s e tumescence a t base ( F i g . 70  c)....  C_. e x p l e t a 4 (3) Pala without 5 (8)  a tumescence a t the base  5 6  R i g h t paramere not b i f u r c a t e . . . .  6 ( 7 ) Seventh abdominal tergum d o r s a l l y w i t h a c a u d a l t r a n s v e r s e t u f t of h a i r s ( F i g . 65 A) 7 (6)  C_.  andersoni  Seventh abdominal tergum d o r s a l l y w i t h o n l y t u f t of h a i r s ( F i g . 66 B)  and  caudal  . .. . C_. b l a i s d e l l i  8 (5). R i g h t paramere b i f u r c a t e . . . . .  9  9 ( 1 0 ) Hind l e g w i t h the l a s t segment ( t a r s u s 2)  entirely  b l a c k or dark brown, r i g h t paramere w i t h - t h e  proximal  p r o j e c t i o n much t h i n n e r t h a n the d i s t a l p r o j e c t i o n ( F i g . 71 e)  C_.  dakotensis  10 ( 9 ) Combination of c h a r a c t e r s not as above  11  11 ( 1 2 ) Median l o b e of the ':(tli• abdomina 1 , t e r gurn d o r s a l l y without  a h a i r t u f t , a t most a few  short h a i r s  appear ( F i g . 64 B ) , d i s t a l p r o j e c t i o n of the  right  paramere i r r e g u l a r l y curved a t the t i p ( F i g , 71 b ) , proximal p r o j e c t i o n roundish  C_.  kuiterti  12 (11) Combination of c h a r a c t e r s not as above 13 (14)  13  P o s t e r i o r pegs of h i n d femur i n 2-3 rows or i n a clump, t h e i r number more t h a n 12, p a l a r pegs o f t e n i n a b r o k e n or almost b r o k e n row  C.  bifida  218 14 (13) P o s t e r i o r pegs of h i n d femur u s u a l l y i n one row, t h e i r number l e s s t h a n 1 2 , p a l a r pegs i n a r e g u l a r row  _C. u t a h e n s i s  219  a  F i g . 6 4 . D o r s a l v i e w of p o s t e r i o r abdominal t e r g a of male i n C. b i f i d a (A) and C. k u i t e r t i ( B ) .  219 b  220 a  F i g . 6 5 . D o r s a l v i e w of p o s t e r i o r abdominal t e r g a of male i n C_. a n d e r s o n i  (A) and C_. u t a h e n s i s .  B  221 a  P i g . 66. D o r s a l v i e w of p o s t e r i o r abdominal t e r g a of male i n C. d a k o t e n s i s (A) and C_. b l a i s d e l l i ( B ) .  221 b  222 a  F i g . 67. D o r s a l v i e w of p o s t e r i o r abdominal t e r g a of male i n _C. w i l e y a e (A) and _C. e x p l e t a ( B ) .  223 a  F i g . 6 8 . I n t r a s p e c i f i c v a r i a t i o n i n arrangement o f p a l a r pegs i n C_. b i f i d a . Specimens from A l b e r t a ( a ) , Utah ( b ) , and B r i t i s h Columbia ( c , d ) .  224  a  F i g . 69. Arrangement of p a l a r pegs i n _C. k u i t e r t i ( a ) , _C. a n d e r s o n i ( b ) , C_. u t a h e n s i s ( c ) , and C_. d a k o t e n s i s (d).  225 a  F i g . 70. Arrangement of p a l a r pegs i n C. b l a i s d e l l i ( a ) , C_. w i l e y a e  ( b ) , and C. e x p l e t a ( c ) .  225 b  226 a  F i g . 7 1 . T y p i c a l shapes o f the r i g h t parameres i n C e n o c o r i x a s p e c i e s , a - C_. b i f i d a ; b = C. k u i t e r t i ; c = £. a n d e r s o n i ; d = _C. u t a h e n s i s ; e = C_. d a k o t e n s i s ; f = C_. b l a i s d e l l i ; g = _C. w i l e y a e ; h = C_. e x p l e t a .  226 b  227 a  F i g . 7 2 . I n t r a s p e c i f i c v a r i a t i o n i n shape o f r i g h t paramere i n C. b i f i d a . Specimens from B r i t i s h Columb i a , C h i l c o t i n , Beeche's P r a i r i e , Lake Lye ( a - d ) ; B r i t i s h Columbia, C a r i b o o , Long Lake ( e - h ) ; Utah, Wasatch Co., S t r a w b e r r y R e s e r v o i r ( i - j ) ; A l b e r t a , Brooks ( k - l ) .  228  a  F i g - 73- I n t r a s p e c i f i c v a r i a t i o n i n shape of r i g h t paramere of C_. k u i t e r t i (a-d) (specimens from: C a l i f o r n i a , Tuolumne Co., Tioga Pass) and £. a n d e r s o n i (e-1) (specimens from: Washington, Whatcom Co., C u s t e r ) .  228 b  229  a  F i g , 74. I n t r a s p e c i f i c v a r i a t i o n i n shape of r i g h t paramere i n C_. u t a h e n s i s (a-d) (specimens from: a = A l b e r t a , G l e i c h e n ; b-c = A l b e r t a , M e d i c i n e Hat; d = Washington, F r a n k l i n Co., Scootenay R e s e r v o i r ) , _C. d a k o t e n s i s (e-h) (specimens from: A l b e r t a , B r o o k s ) , and C_. b l a i s d e l l i ( i - l ) (specimens from: i - k = B r i t i s h Columbia, Vancouver; 1 = C a l i f o r n i a , Humboldt Co., Clam Beach).  230  a  F i g . 7 5 • I n t r a s p e c i f i c v a r i a t i o n i n shape o f r i g h t paramere i n C_. w i l e y a e (a-d) (specimens from: C a l i f o r n i a , L a s s e n Co., S a i d Lake) and C_. e x p l e t a (e-h) (specimens from: B r i t i s h Columbia, Kamloops a r e a , LB2).  231  APPENDIX I I AUDIOSPECTROGRAPHIC ANALYSIS OF THE STRIDULATORY SIGNALS OF SOME NORTH AMERICAN CORIXIDAE FOUND SYMPATRIC WITH CENOCORIXA V a r i o u s g e n e r a and s p e c i e s o f C o r i x i d a e were found symp a t r i c w i t h C e n o c o r i x a d u r i n g t h e p r e s e n t study. S i n c e some of these o t h e r s p e c i e s were observed  t o s t r i d u l a t e , the  s i g n a l s o f t h e s e were r e c o r d e d and used i n playback: experiments w i t h C e n o c o r i x a  (see Table X I I , page 1 3 4 ) . A n a l y s i s  o f t h e s i g n a l s o f t h e o t h e r t a x a showed t h a t t h e s e  calls  a r e s p e c i e s s p e c i f i c and d i f f e r e n t from C e n o c o r i x a  calls.  The l o c a l i t i e s where o t h e r s t r i d u l a t i n g C o r i x i d a e were found s y m p a t r i c w i t h C e n o c o r i x a , and t h e s i g n a l s o f these t a x a a r e as  follows:  C o r i s e l l a t a r s a l i s (Fieber) Sympatric sis,  s i t u a t i o n s were: C_. b i f i d a , A l b e r t a ; _C. utahen-  A l b e r t a , Utah; C_. d a k o t e n s i s , A l b e r t a ; C_. w i l e y a e , C a l i -  f o r n i a , Nevada, Utah; Male c a l l : ( F i g .  C_. e x p l e t a , A l b e r t a . <7;6 A ) : Recorded a t 24.0°C. B a s i c a l l y a  s i m p l e m u l t i p u l s a t e s i g n a l . However, t h e s i g n a l s a r e u s u a l l y produced i n a sequence o f 3-10 s h o r t c a l l s , each l a s t i n g a p p r o x i m a t e l y 0.5-2 seconds a t 24°C. The f i r s t c a l l s a r e u s u a l l y s h o r t e r t h a n t h e l a t e r ones. P u l s e r a t e a t t h e g i v e n temperature  i s about 60 p u l s e s p e r second. Main  a r e a o f t h e sound i s 3-5 k c / s e c . Female c a l l was n o t o b t a i n e d .  frequency  232  Genus C a l l i c o r i x a The  s i g n a l s of a l l C a l l i c o r i x a species obtained  were  found t o be b a s i c a l l y o f t h e same type w i t h two p a r t s : f a i n t slow beginning ing.  w h i c h a c c e l e r a t e s t o a l o u d e r and f a s t e r end-  Main f r e q u e n c y  area i n a l l s i g n a l s recorded  sec. Only male c a l l s were  was 3-5 k c /  obtained.  _C. v u l n e r a t a ( U h l e r ) . S y m p a t r i c s i t u a t i o n s were: _C. b i f i d a , B r i t i s h Columbia; C.. a n d e r s o n i ,  B r i t i s h Columbia, Wash-  i n g t o n ; C. b l a i s d e l l i , B r i t i s h Columbia, Male c a l l the c a l l  California.  ( F i g . 76 B ) : Recorded a t 23.2°C. Both p a r t s o f  a r e r e l a t i v e l y s h o r t and o f s i m p l e m u l t i p u l s a t e type  with d i s t i n c t pulse i n t e r v a l s . Duration of the f i r s t part at 23.2°C was about 0.7 seconds and t h e second p a r t about 0.3 seconds. The f i r s t p a r t c o n s i s t s o f somewhat i r r e g u l a r .pulses. P u l s e r a t e o f t h e f i r s t p a r t was about 12 and t h e second p a r t about 28 p u l s e s p e r second a t t h e g i v e n t e m p e r a t u r e , C_. a u d e n i Hungerford. S y m p a t r i c s i t u a t i o n s were: C_. b i f i d a , B r i t i s h Columbia, A l b e r t a ; _C. k u i t e r t i ,  California;  C_. u t a h e n s i s , A l b e r t a ; C_. d a k o t e n s i s , A l b e r t a ; C_. w i l e y a e , C a l i f o r n i a ; _C. e x p l e t a , B r i t i s h Columbia, A l b e r t a . Male c a l l call  ( F i g . 77 A ) : Recorded a t 22.5°C C. a u d e n i  i s much l o n g e r i n d u r a t i o n t h a n t h a t o f _C. v u l n e r a t a :  the f i r s t p a r t l a s t s about 1.5 seconds and t h e second p a r t about 1.0 seconds a t 22.5°C. P u l s e r a t e s a t t h e g i v e n tem^ perature and  f o r t h e f i r s t and t h e second p a r t s a r e about 20  30 p u l s e s p e r second, r e s p e c t i v e l y , _C. t e t o n i H u n g e r f o r d . Sympatric s i t u a t i o n s were: _C. b i -  f i d a , Utah; C_. u t a h e n s i s , Utah ( n o t i n t h e same l a k e , b u t i n  233 the same g e o g r a p h i c Male c a l l  a r e a ) ; _C. w i l e y a e , Utah.  (Fig.  77  B): Recorded a t  22.0°C. Only one  s a t i s f a c t o r y r e c o r d i n g made. A c c o r d i n g t o t h i s the  first  p a r t of the c a l l i s v e r y f a i n t and n o t h i n g can be s t a t e d about i t s l e n g t h . The  second p a r t of the c a l l i s of t y p i c a l  C a l l i c o r i x a s i g n a l form. D u r a t i o n of the second p a r t i s about 0.5  seconds and the p u l s e r a t e about 34 p u l s e s  per  second a t 22.0°C.  Genus S i g a r a S e v e r a l s p e c i e s of the genus were found s y m p a t r i c Cenocorixa,  but o n l y two o f these s p e c i e s were observed  with to  stridulate. S_. omani ( H u n g e r f o r d ) . kuiterti,  Sympatric  s i t u a t i o n s were: C_.  C a l i f o r n i a ; _C. a n d e r s o n i , B r i t i s h Columbia, Wash-  i n g t o n ; C_. b l a i s d e l l i ,  B r i t i s h Columbia; C_. w i l e y a e ,  Calif-  ornia . Male c a l l  ( F i g . 78 A ) : Recorded a t 21.2°C. Simple m u l t i -  p u l s a t e c a l l w i t h s l i g h t l y f a i n t e r b e g i n n i n g t h a n the end w i t h v e r y s h o r t , almost n o n - e x i s t i n g p u l s e i n t e r v a l s . of the s i g n a l i s about 1.5  Duration  seconds and p u l s e r a t e about 24  p u l s e s per second a t the g i v e n temperature. a r e a i s about 4-5  and  k c / s e c . Only male c a l l was  Main  frequency  obtained f o r  the s p e c i e s . S_. nevadensis  ( W a l l e y ) . Sympatric  s i t u a t i o n s were: _C.  b i f i d a , Utah; C_. u t a h e n s i s , Utah; C_. w i l e y a e , Utah. However, _S. nevadensis  d i d not occur i n the :same...lakes'iwith ariy'.lof the  mentioned C e n o c o r i x a  s p e c i e s , but was  found i n the same geo-  234  graphic area. Male c a l l  ( F i g . 78 B ) : Recorded a t 22.2°C. V e r y much  l i k e t h e c a l l o f _S. omani, w i t h s l i g h t l y f a i n t e r b e g i n n i n g t h a n t h e end, but i n S_. nevadensis  c a l l the pulse i n t e r v a l s  are d i s t i n c t . D u r a t i o n o f t h e s i g n a l was about 1.5 seconds and p u l s e r a t e about 22 p u l s e s p e r second a t t h e g i v e n temp e r a t u r e . M a i n f r e q u e n c y a r e a o f t h e sound i s 4-5 k c / s e c . Female c a l l  ( F i g . 78 C ) : Recorded a t 21.0°C. A s i m p l e  m u l t i p u l s a t e s i g n a l which i s much f a i n t e r t h a n t h e male s i g n a l . Pulse i n t e r v a l s are d i s t i n c t ,  but some i r r e g u l a r i t i e s  o c c u r . D u r a t i o n o f t h e s i g n a l was about 2.5 seconds and p u l s e r a t e about 16 p u l s e s p e r second a t t h e g i v e n  temperature.  M a i n f r e q u e n c y a r e a o f t h e sound i s 4-5 k c / s e c . The  f u n c t i o n o f t h e male and female s i g n a l s i n _S. neva-  d e n s i s was observed  t o be t o f a c i l i t a t e p a i r f o r m a t i o n , i . e .  the f u n c t i o n o f t h e s i g n a l s seems t o be t h e same as i n t h e genus  Cenocorixa.  235  a  F i g . 76. Sound spectrograms of the male c a l l s of C o r i s e l l a t a r s a l i s (A) and C a l l i c o r i x a  vulnerata  ( B ) . _C. t a r s a l i s s i g n a l r e c o r d e d a t 24.0°C, specimen from: Utah, Box E l d e r Co., Bear R i v e r . C_. v u l n e r a t a s i g n a l r e c o r d e d a t 23.2°C, Columbia,  Fig.  specimen from: B r i t i s h  Vancouver.  77. Sound spectrograms of the male c a l l s of  C a l l i c o r i x a a u d e n i (A) and C_. t e t o n i ( B ) . CJ. audeni s i g n a l recorded.;at 22.5°C,  specimen from: A l b e r t a ,  C_. t e t o n i s i g n a l r e c o r d e d a t 22.0°C, Wasatch Co., S t r a w b e r r y R e s e r v o i r .  Brooks.  specimen from: Utah,  235 b  O  1 O 3H  i  «  iiiiiiili!  M  i  1 SECONDS  76  1  SECONDS  77  13  236  Q fe O  o  5i  3  w  w  1 "T"  w  2  Hi  u  o  B  M  S E C O N D S  F i g . 7 8 . Sound spectrograms of t h e s i g n a l s o f S i g a r a omani (A) and S_. n e v a d e n s i s (B = male c a l l , C = female c a l l ) . S_. omani s i g n a l r e c o r d e d a t 21.2°C, specimen from: Washington, Whatcom Co., C u s t e r . S_. n e v a d e n s i s s i g n a l s r e c o r d e d a t 22.2°C (male) and 21.0°C ( f e m a l e ) , specimens from: Utah, Box E l d e r Co., Bear R i v e r .  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0101890/manifest

Comment

Related Items