UBC Theses and Dissertations

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UBC Theses and Dissertations

Territorial aggression among males of three syrphid species Fitzpatrick, Sheila M. 1981

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TERRITORIAL AGGRESSION AMONG MALES OF THREE SYRPHID SPECIES by SHEILA M. FITZPATRICK B . S c . ( A g r . ) , U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r , 1979 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department o f P l a n t S c i e n c e ) We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA November 1981 © S h e i l a M. F i t z p a t r i c k , 1981 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s thesis for s c h o l a r l y purposes may be granted by the head of my department or by h i s or her representatives. It i s understood that copying or publ i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date ^ £ IO/&I  ABSTRACT Among t e r r i t o r i a l s y r p h i d s , Eumerus t u b e r c u l a t u s (Rond.) m a l e s a r e a l w a y s l e s s a g g r e s s i v e t h a n Merodon e q u e s t r i s (Fab.) and E r i s t a l i s t e n a x (L.) m a l e s . T h i s a g g r e s s i v e g r a d i e n t i s m a i n t a i n e d d e s p i t e t h e f a c t t h a t t h e a g g r e s s i v e i n t e n s i t y of a l l t h r e e s p e c i e s i n c r e a s e s w i t h t h e d e n s i t y o f c o n s p e c i f i e s , v a r i e s w i t h i n s e c t age and s t a g e , and c e a s e s i f t e m p e r a t u r e s f a l l below a c e r t a i n c r i t i c a l l e v e l o r i f s u n l i g h t d i s a p p e a r s . P o s s i b l e r e a s o n s f o r t h e d i f f e r e n c e i n t h e i n h e r e n t l e v e l o f a g g r e s s i o n a r e d i s c u s s e d . M a l e s o f a l l t h r e e s p e c i e s r e c o g n i z e d c o n s p e c i f i e f e m a l e s t h r o u g h a c o m b i n a t i o n of v i s u a l and b e h a v i o u r a l c u e s . A t e r r i t o r i a l male a p p r o a c h e d a l l o t h e r i n t r u d e r s a g g r e s s i v e l y but a t t e m p t e d t o mate w i t h them i f , l i k e f e m a l e s , t h e i n t r u d e r s d i d not r e s p o n d t o t h e m a l e ' s a p p r o a c h . D i f f e r e n c e s i n b e h a v i o u r p a t t e r n s among s p e c i e s a r e t e n t a t i v e l y t r a c e d t o d i f f e r e n t e n e r g y b u d g e t s and m a t i n g s t r a t e g i e s . W i t h i n e a c h s p e c i e s , m ales and f e m a l e s show d i f f e r e n t t e m p e r a t u r e t h r e s h o l d s f o r a c t i v i t y . T h i s f i n d i n g i s d i s c u s s e d i n t e r m s of e n e r g y r e q u i r e m e n t s and r e s e r v e s . The f i n a l two s e c t i o n s of t h e t h e s i s d e a l w i t h t h e a g r i c u l t u r a l i m p l i c a t i o n s of t h e s e r e s u l t s and w i t h p o s s i b i l i t i e s f o r f u t u r e s t u d i e s . i i i TABLE OF CONTENTS ABSTRACT i i L I S T OF TABLES v i L I S T OF FIGURES . . . v i i ACKNOWLEDGEMENTS . . v i i i I n t r o d u c t i o n 1 T e r r i t o r i a l i t y d e f i n e d 3 I n s e c t t e r r i t o r i a l i t y 6 M a t e r i a l s and Methods 22 The N a r c i s s u s B u l b F l y , Merodon e q u e s t r i s 30 Im p o r t a n c e 30 B i o l o g y and L i f e H i s t o r y 30 R e s u l t s 39 C h a r a c t e r i s t i c s o f a T e r r i t o r y 39 T e r r i t o r i a l B e h a v i o u r s 43 V a r i a t i o n s i n T e r r i t o r i a l B e h a v i o u r P a t t e r n s 47 1. S u n l i g h t and t e m p e r a t u r e 50 2. A d d i t i o n a l w e a t h e r e f f e c t s 51 3. C r o w d i n g by c o n s p e c i f i c s 52 4. I n s e c t age and s t a g e 54 R e c o g n i t i o n of I n t r u d e r s 62 The L e s s e r B u l b F l y , Eumerus t u b e r c u l a t u s 64 Im p o r t a n c e 64 B i o l o g y and L i f e H i s t o r y 65 R e s u l t s 73 i v C h a r a c t e r i s t i c s of a T e r r i t o r y 73 T e r r i t o r i a l B e h a v i o u r s 74 V a r i a t i o n s i n T e r r i t o r i a l B e h a v i o u r P a t t e r n s 81 R e c o g n i t i o n of I n t r u d e r s 83 The d r o n e f l y , E r i s t a l i s t e n a x 84 I m p o r t a n c e , B i o l o g y and L i f e H i s t o r y 84 R e s u l t s 89 C h a r a c t e r i s t i c s of a T e r r i t o r y 89 T e r r i t o r i a l B e h a v i o u r s 91 V a r i a t i o n s . i n T e r r i t o r i a l B e h a v i o u r P a t t e r n s 97 1 . S u n l i g h t and t e m p e r a t u r e 97 2. C r o w d i n g by c o n s p e c i f i c s 98 3. T e r r i t o r y t y p e 100 4. I n s e c t age and s t a g e ' 101 R e c o g n i t i o n of I n t r u d e r s 102 D i s c u s s i o n 104 V a r i a t i o n i n A g g r e s s i o n 104 R e c o g n i t i o n of F e m a l e s 111 O t h e r D i f f e r e n c e s Between S p e c i e s 113 I m p l i c a t i o n s f o r A g r i c u l t u r e 116 A r e a s f o r f u t u r e s t u d y 117 L i t e r a t u r e c i t e d 120 A p p e n d i x I . S o l a r e l e v a t i o n 131 A p p e n d i x I I . B e h a v i o u r a l d a t a 132 A1 133 A2 1 34 A3 135 V B l . . ... . . . . . . 1 3 6 B 2 . 137 B 3 . . . . . 1 38 C1 1 39 C 2 . . . 1 4 0 C3 . . . . .... .141 v i L I S T OF TABLES T a b l e I . B e h a v i o u r s of male s y r p h i d s 25 T a b l e I I . Time a l l o c a t i o n by an M. e q u e s t r i s male 50 T a b l e I I I . R e s p o n s e s of M. e q u e s t r i s m a l e s . t o i n t r u d e r s .. 53 T a b l e IV. R e s p o n s e s of E. t u b e r c u l a t u s males t o i n t r u d e r s 77 T a b l e V. Time a l l o c a t i o n by an E. t e n a x male 94 v i i L I S T OF FIGURES F i g u r e 1. Merodon e q u e s t r i s and bumblebee . . ...... 32 F i g u r e 2. M a t i n g M. e q u e s t r i s p a i r 34 F i g u r e 3. M. e q u e s t r i s : S t a g e s i n m a t i n g 37 . F i g u r e 4. Map o f t h e s t u d y s i t e 41 F i g u r e 5. B e h a v i o u r s o f t e r r i t o r i a l M. e q u e s t r i s m a l e s ... 44 F i g u r e 6. P a t r o l r o u t e s of M. e q u e s t r i s m a l e s 48 F i g u r e 7. M. e q u e s t r i s t e r r i t o r y s i z e i n r e s p o n s e t o c r o w d i n g 55 F i g u r e 8. Newly-emerged M. e q u e s t r i s male 58 F i g u r e 9. Eumerus t u b e r c u l a t u s and h a l i c t i d 66 F i g u r e 10. E. t u b e r c u l a t u s male 68 F i g u r e 11. M a t i n g E. t u b e r c u l a t u s p a i r 71 F i g u r e 12. E. t u b e r c u l a t u s t e r r i t o r y 75 F i g u r e 13. B e h a v i o u r s of t e r r i t o r i a l E . t u b e r c u l a t u s m a l e s 78 F i g u r e 14. E r i s t a l i s t e n a x and A p i s m e 1 1 i f e r a . . 8 5 F i g u r e 15. A m a t i n g E. t e n a x p a i r 87 F i g u r e 16. E. t e n a x h o v e r i n g 92 F i g u r e 17. E. t e n a x male on h o r i z o n t a l t e r r i t o r y 95 v i i i ACKNOWLEDGEMENTS In o r d e r t o do t h i s s t u d y , I had t o s t o p " l o o k i n g " a t i n s e c t s and b e g i n " s e e i n g " what t h e y were d o i n g . My g u i d e t o t h e r e a l m o f s e e i n g was Dr.W.G. W e l l i n g t o n , who a l s o p r o v i d e d me w i t h a s t u d y s i t e , an e l a b o r a t e c o m b i n a t i o n of camera and f l a s h u n i t s , m o r a l and f i n a n c i a l s u p p o r t , and much good humour. He t o o k many of t h e p h o t o g r a p h s w h i c h a p p e a r h e r e , and r e a d i l y c h a n g e d h a t s from p h o t o g r a p h e r t o a b l e - b o d i e d f i e l d a s s i s t a n t . He and h i s w i f e M a r g r e t , d a u g h t e r K a t h y , and son S t e p h e n were a c o n t i n u a l s o u r c e o f s u s t e n a n c e and e n c o u r a g e m e n t ; I am e x t r e m e l y g r a t e f u l t o them a l l . I a l s o had s e v e r a l t e a c h i n g a s s i s t a n t s h i p s i n t h e d e p a r t m e n t of P l a n t S c i e n c e . I am g r a t e f u l t o D r s . Copeman, E l l i o t t , M y e rs, Todd and R u n e c k l e s f o r t h e s e p o s i t i o n s and t h e i r m o r a l s u p p o r t . I thank D e b o r a h H e n d e r s o n f o r s h a r i n g h e r f i e l d p l o t a t U.B.C. w i t h me, Mark Ridgway and Lee Gass f o r h e l p f u l d i s c u s s i o n s a b o u t a n a l y z i n g b e h a v i o u r a l d a t a , L a u r a R i c h a r d s f o r a l l o w i n g me t o q u o t e h e r u n p u b l i s h e d work, and Dave Z i t t i n , whose i n e x a u s t i b l e computer w i z a r d r y was much a p p r e c i a t e d . I have e n j o y e d t h e w i t and c o m p a n i o n s h i p o f t h e g r a d u a t e s t u d e n t p o p u l a t i o n a t t h e I n s t i t u t e of A n i m a l R e s o u r c e E c o l o g y and, i n p a r t i c u l a r , of P e t e r M o r r i s o n and Ken L e r t z m a n , who were a l w a y s u n c a n n i l y s u p p o r t i v e a t j u s t t h e r i g h t moment. F i n a l l y , I t h a nk P e t e r Cahoon, who h e l p e d me t o see what was r e a l l y t h e r e . 1 INTRODUCTION T e r r i t o r i a l a g g r e s s i o n has o f t e n been s t u d i e d i n an e v o l u t i o n a r y c o n t e x t , where h y p o t h e s e s d e a l w i t h t h e r e p r o d u c t i v e s u c c e s s or f i t n e s s of t e r r i t o r i a l a n i m a l s . The e v o l u t i o n a r y a p p r o a c h f a c i l i t a t e s i n t e r e s t i n g t h e o r e t i c a l c o m p a r i s i o n s and many n o w - f a m i l i a r o p t i m a l i t y arguments ( e . g . , P a r k e r , 1978). But o t h e r , more immediate a s p e c t s o f t e r r i t o r i a l a g g r e s s i o n a r e of e q u a l i n t e r e s t . A t e r r i t o r i a l a n i m a l i s c o n t i n u a l l y f a c e d w i t h a dynamic e n v i r o n m e n t and must r e s p o n d a p p r o p r i a t e l y i n o r d e r t o s u r v i v e . In t h i s f i e l d s t u d y , I i n v e s t i g a t e d t h e r e s p o n s e s of t e r r i t o r i a l m a les t o c h a n g i n g e x t e r n a l and i n t e r n a l f a c t o r s by o b s e r v i n g c h a n g e s i n p a t t e r n s of t e r r i t o r i a l b e h a v i o u r and s u b s e q u e n t f l u c t u a t i o n s i n a g g r e s s i v e i n t e n s i t y . I o b s e r v e d t h r e e s p e c i e s o f s y r p h i d f l i e s : Merodon  e q u e s t r i s ( F a b . ) , Eumerus t u b e r c u l a t u s ( R o n d . ) , and E r i s t a l i s  t e n a x ( L . ) . P r e l i m i n a r y o b s e r v a t i o n s showed t h a t males o f t h e f i r s t and t h i r d s p e c i e s were a l w a y s more a g g r e s s i v e than m a l e s of t h e s e c o n d . T h e s e o b s e r v a t i o n s l e d t o t h e f o r m a t i o n o f my f i r s t h y p o t h e s i s , namely, t h a t males have a s p e c i e s - s p e c i f i c i n h e r e n t l e v e l of t e r r i t o r i a l a g g r e s s i v e n e s s w h i c h v a r i e s i n r e s p o n s e t o c h a n g e s i n e x t e r n a l f a c t o r s , s u c h as weather and p o p u l a t i o n d e n s i t y , and i n t e r n a l f a c t o r s , s u c h as i n s e c t age. My s e c o n d h y p o t h e s i s a r o s e from t h e c o m b i n a t i o n of my own f i e l d o b s e r v a t i o n s and a c o n t r o v e r s y among e n t o m o l o g i s t s who s t u d y i n s e c t t e r r i t o r i a l i t y . The c o n t r o v e r s y c o n c e r n s t h e i n t e n t of a t e r r i t o r i a l male as he a p p r o a c h e s i n t r u d e r s on h i s 2 t e r r i t o r y . Some w o r k e r s have p o s t u l a t e d t h a t a l l s u c h a p p r o a c h e s a r e made w i t h m a t i n g i n t e n t b e c a u s e m a l e s c a n n o t r e c o g n i z e i n t r u d e r s a t a d i s t a n c e . O t h e r s d i s a g r e e , b e l i e v i n g i n s t e a d t h a t t e r r i t o r i a l m a les a r e a b l e t o d i s t i n g u i s h f e m a l e s , and t h a t a p p r o a c h e s t o w a r d a l l o t h e r i n t r u d e r s a r e t r u l y a g g r e s s i v e ( s e e pp.11.1-113). T h e r e f o r e my s e c o n d h y p o t h e s i s i s t h a t t e r r i t o r i a l s y r p h i d m ales c a n and do d i s t i n g u i s h f e m a l e s f r om a l l o t h e r i n t r u d e r s , and t h a t t h e r e i s a d i f f e r e n c e between s e x u a l and a g g r e s s i v e a p p r o a c h e s . A d d i t i o n a l r e s u l t s of t h i s s t u d y f a l l o u t s i d e t h e b o u n d a r i e s o f t h e p r e c e d i n g two h y p o t h e s e s . T h e s e r e s u l t s a r e d i s c u s s e d i n r e l a t i o n t o t h e i r p h y s i o l o g i c a l and e v o l u t i o n a r y i m p l i c a t i o n s . 3 TERRITORIALITY DEFINED A t t e m p t s t o d e f i n e t e r r i t o r i a l i t y a r e a l m o s t as numerous as t h e known t y p e s of t e r r i t o r i a l a n i m a l s . In f a c t , Kaufman (1971) s t a t e d t h a t , "no s i m p l i f i e d d e f i n i t i o n of t e r r i t o r i a l i t y y e t a d v a n c e d can c o v e r a l l r e l a t e d k i n d s o f b e h a v i o u r known, and p e r h a p s i t i s n a i v e t o l o o k f o r one". N o b l e (1939) d e f i n e d a t e r r i t o r y as "any d e f e n d e d a r e a " . W i l s o n (1975) augmented t h i s d e f i n i t i o n t o "an a r e a o c c u p i e d more or l e s s e x c l u s i v e l y by an a n i m a l or g r o u p of a n i m a l s by means of r e p u l s i o n t h r o u g h o v e r t d e f e n s e o r a d v e r t i s e m e n t " . D a v i e s (1978a) r e c o g n i z e d t e r r i t o r i e s "whenever i n d i v i d u a l a n i m a l s o r g r o u p s a r e s p a c e d out more t h a n would be e x p e c t e d from a random o c c u p a t i o n of s u i t a b l e h a b i t a t s " , and added t h a t t e r r i t o r i e s were m a i n t a i n e d e i t h e r by o v e r t a g g r e s s i o n or by a d v e r t i s e m e n t s s u c h as s c e n t m a r k i n g s . Brown and O r i a n s (1970) u s e d t h r e e c r i t e r i a t o d e f i n e a t e r r i t o r y : 1) t h e a r e a must be f i x e d , a l t h o u g h i t s e x a c t l o c a t i o n may change o v e r t i m e ; 2) i t must be d e f e n d e d e i t h e r by o v e r t d e f e n s e o r a d v e r t i s e m e n t and 3) as a r e s u l t o f d e f e n s e , i t must be a l m o s t e x c l u s i v e l y u s e d by t h e r e s i d e n t . However, some a n i m a l s , e.g., c a t s ( L e y h a u s e n , 1968) and chipmunks ( G e t t y , 1981) m a i n t a i n t e r r i t o r i e s w h i c h o v e r l a p s p a t i a l l y but n o t t e m p o r a l l y . In s u c h c a s e s , a t e r r i t o r y i s n o t e x c l u s i v e l y u s e d by t h e r e s i d e n t . T h e r e f o r e , t h e common f a c t o r i n e a c h of t h e p r e c e d i n g d e f i n i t i o n s i s d e f e n s e o f s p a c e and N o b l e ' s c o n c i s e d e f i n i t i o n i s t h e most c o m p r e h e n s i v e . D e f e n s i v e b e h a v i o u r s a r e not u n i q u e t o t e r r i t o r i a l s i t u a t i o n s . L e y h a u s e n (1968) h y p o t h e s i z e d t h a t s u c h b e h a v i o u r s 4 a r e an e x t e n s i o n o f t h o s e u s e d t o m a i n t a i n i n d i v i d u a l d i s t a n c e , and r e l a t e d t h e f o l l o w i n g f a b l e t o e x p l a i n t h e i n d i v i d u a l d i s t a n c e c o n c e p t . "One v e r y c o l d n i g h t , a g r o u p of p o r c u p i n e s were h u d d l e d t o g e t h e r f o r warmth. However, t h e i r s p i n e s made p r o x i m i t y u n c o m f o r t a b l e , so t h e y moved a p a r t and g o t c o l d . A f t e r s h u f f l i n g r e p e a t e d l y i n and p u t , t h e y e v e n t u a l l y f o u n d a d i s t a n c e a t w h i c h t h e y c o u l d s t i l l be c o m f o r t a b l y warm w i t h o u t g e t t i n g p r i c k e d . " The moveable h a l o w h i c h i s i n d i v i d u a l d i s t a n c e becomes a t e r r i t o r y when an a n i m a l a t t a c h e s i t s e l f t o an a r e a ( o p . c i t . ) . T e r r i t o r i a l s p a c e , a l t h o u g h f i x e d , i s not r i g i d l y s o . J u l i a n H u x l e y (1934) m e t a p h o r i c a l l y d e s c r i b e d a t e r r i t o r y a s an e l a s t i c d i s c w h i c h c o n t i n u a l l y r e s p o n d s t o t h e dynamic community o u t s i d e i t s c i r c u m f e r e n c e by c h a n g i n g shape as n e i g h b o u r s e n c r o a c h and r e t r e a t . In p r a c t i c e , t e r r i t o r i a l b o u n d a r i e s a r e r a r e l y c i r c u l a r ; u s u a l l y t h e y f o l l o w n a t u r a l l i n e s l i k e s t r e a m s , r i d g e s and v e g e t a t i o n b o r d e r s . Sometimes a t e r r i t o r y i s n o t an a r e a i n s i d e a f i x e d b o undary b ut "a network of p a t h s and p l a c e s t o v i s i t " ( L e y h a u s e n , 1968). The d i s t i n c t i o n between an a n i m a l ' s t e r r i t o r y and i t s home rang e v a r i e s w i t h a n i m a l s p e c i e s . A t e r r i t o r y may o c c u p y p a r t o r a l l o f an a n i m a l ' s home r a n g e . Brown and O r i a n s (1970) d e f i n e d a home ran g e as " t h e a r e a i n w h i c h an a n i m a l n o r m a l l y l i v e s , e x c l u s i v e o f m i g r a t i o n s , e m i g r a t i o n s or u n u s u a l e r r a t i c w a n d e r i n g s " . I f t h e e n t i r e home range i s d e f e n d e d ( i . e . , i s a t e r r i t o r y ) , home r a n g e s of two a n i m a l s do not o v e r l a p . But i f t h e b o u n d a r i e s of an a n i m a l ' s t e r r i t o r y and i t s home range a r e 5 n o t c o n t i g u o u s , two home r a n g e s may o v e r l a p . 6 INSECT TERRITORIALITY In h i s r e v i e w of t e r r i t o r i a l i t y , W i l s o n (1975) s t a t e d t h a t t e r r i t o r i a l i t y has "a p a t c h y p h y l o g e n e t i c d i s t r i b u t i o n . I t o c c u r s w i d e l y t h r o u g h t h e v e r t e b r a t e s and i s common, but f a r l e s s g e n e r a l , among t h e a r t h r o p o d s , i n c l u d i n g e s p e c i a l l y t h e c r u s t a c e a n s and t h e i n s e c t s " . As more work i s done w i t h i n s e c t s , however, e v i d e n c e a c c u m u l a t e s t o i n d i c a t e t h a t , t e r r i t o r i a l i t y i n t h e phylum I n s e c t a i s more w i d e s p r e a d t h a n p r e v i o u s l y b e l i e v e d . The t e r r i t o r i a l b e h a v i o u r of m a t e - s e e k i n g m a l e s i s o f p a r t i c u l a r i n t e r e s t . O t h e r t y p e s of t e r r i t o r i a l i t y , e.g., d e f e n s e o f b r o o d and n e s t a r e a s by s o c i a l i n s e c t s l i k e bees (Wynne-Edwards, 1962), t e r m i t e s and a n t s ( W i l s o n , 1971), o r o f f o r a g i n g a r e a s by m a n t i d l a r v a e (MacKinnon, 1969) w i l l n ot be d e a l t w i t h h e r e . M a l e t e r r i t o r i a l i t y i n i n s e c t s was f i r s t d e s c r i b e d by W i l l i a m s o n (1899, i n J a c o b s , 1955), who n o t i c e d t h e a g g r e s s i v e b e h a v i o u r o f b r i g h t l y - c o l o u r e d d r a g o n f l i e s . However, e a r l y work on t h e s u b j e c t was done by o r n i t h o l o g i s t s i n t e r e s t e d i n t h e t e r r i t o r i a l b e h a v i o u r of b i r d s ( N o b l e , 1939, N i c e , 1941, Moore, 1952). S i n c e t h e n , more e n t o m o l o g i s t s have become aware o f t e r r i t o r i a l i t y , f i r s t i n t h e O d o n a t a , and s u b s e q u e n t l y i n o t h e r o r d e r s . M a l e d r a g o n f l i e s become t e r r i t o r i a l a f t e r d i s p e r s i n g from t h e i r emergence ( t e n e r a l m o l t ) s i t e t o an a q u a t i c a r e a . A r e s i d e n t male p a t r o l s h i s t e r r i t o r y , a p p r o a c h i n g c o n s p i c u o u s o b j e c t s , c h a s i n g i n t r u d e r s and, i n f r e q u e n t l y , d a r t i n g a f t e r 7 p r e y . When a male e n c o u n t e r s a f e m a l e , he g r a s p s h e r and c o p u l a t e s , e i t h e r i n t h e a i r w i t h i n o r nea r h i s t e r r i t o r y ( J a c o b s , 1955), o r s e t t l e s on t h e g r o u n d away from i t ( P a j u n e n , 1966b). L a t e r he g u a r d s h e r w h i l e she o v i p o s i t s . C o n s p e c i f i c m a l e s a n d . a l i e n s r e c e i v e d i f f e r e n t . t r e a t m e n t . The f o r m e r a r e met w i t h a t h r e a t d i s p l a y c o n s i s t i n g of a head-on a t t a c k and p h y s i c a l c o n t a c t . I n t r u d i n g c o n s p e c i f i c s u s u a l l y t u r n t o f a c e t h e a t t a c k i n g r e s i d e n t , and t h e two c i r c l e r e p e a t e d l y , a p p a r e n t l y t r y i n g t o f o r c e e a c h o t h e r t o l o s e h e i g h t and d r o p i n t o t h e w a t e r ( P a j u n e n , 1964). B o t h m a l e s g r a s p and b i t e a t e a c h o t h e r when p o s s i b l e . A l i e n s c o m p a r a b l e i n s i z e t o t h e r e s i d e n t a r e c h a s e d t o a t e r r i t o r y b o u n d a r y , but t h o s e much l a r g e r t h a n t h e r e s i d e n t a r e u s u a l l y l e f t a l o n e (op. c i t . ) . S i m i l a r b e h a v i o u r has been o b s e r v e d among t e r r i t o r i a l Z y g o p t e r a n m a l e s ( J o h n s o n , 1962, P a j u n e n , 1966a, B i c k and B i c k , 1975, A l c o c k , 1979). B e c a u s e a r e s i d e n t ' s r e a c t i o n t o an i n t r u d e r depends on t h e l a t t e r ' s i d e n t i t y , " t e r r i t o r i a l b e h a v i o u r i s m o d u l a t e d by t h e d i s c r i m i n a t o r y a b i l i t y o f t h e o c c u p a n t " (Kormondy, 1961). A l l r e s e a r c h e r s a g r e e t h a t r e c o g n i t i o n i s p r i m a r i l y v i s u a l , a f a c t w h i c h i s s u p p o r t e d by t h e o b s e r v a t i o n t h a t m a l e s a p p a r e n t l y d i s t i n g u i s h a l i e n s f r o m c o n s p e c i f i c s on t h e b a s i s o f s i z e ( P a j u n e n , 1964), and t h a t male-male a t t e m p t e d c o p u l a t i o n s a r e more f r e q u e n t i n s e x u a l l y u n i m o r p h i c s p e c i e s (Moore, 1952). However, male " m i s t a k e s " a l s o o c c u r i n d i m o r p h i c s p e c i e s , a f a c t w h i c h has l e d some r e s e a r c h e r s ( e . g . , Kormondy, 1961) t o c o n c l u d e t h a t a g g r e s s i v e a t t a c k s a r e a l w a y s s e x u a l l y m o t i v a t e d . 8 T h e r e a p p e a r t o be more- f a c t o r s i n v o l v e d i n r e c o g n i t i o n t h a n j u s t c o l o u r p a t t e r n ; I t o ( i 9 6 0 ) o b s e r v e d a " n o r m a l " e n c o u n t e r , i n s t e a d of t h e a g g r e s s i v e a t t a c k he e x p e c t e d , between a male-t y p e f e m a l e and a n o r m a l l y - m a r k e d male. O t h e r i m p o r t a n t c u e s may be m a r k i n g s v i s i b l e o n l y i n t h e u l t r a - v i o l e t ( S i l b e r g l i e d , 1979), f l i g h t p a t t e r n and body form ( P a j u n e n , 1964). In a d d i t i o n t o v a r y i n g w i t h sex and s p e c i e s of i n t r u d e r , a r e s i d e n t ' s r e a c t i o n t o i n t r u d e r s depends on s i t e t e n a c i t y o f t h e r e s i d e n t ( J a c o b s , 1955, I t o , 1960, Kormondy, 1961, P a j u n e n , 1964), p o p u l a t i o n d e n s i t y (Moore, 1952, P a j u n e n , 1966a, b ) , and. e n v i r o n m e n t a l f a c t o r s (Moore, 1952, I t o , 1960, P a j u n e n , 1964). A r e s i d e n t ' s a g g r e s s i v e i n t e n s i t y i n c r e a s e s w i t h s i t e t e n a c i t y ( i . e . , l e n g t h o f r e s i d e n c e ) and, t o a p o i n t , w i t h i n c r e a s i n g p o p u l a t i o n d e n s i t y . When p o p u l a t i o n s of C a l y o p t e r i x m a l e s became v e r y d e n s e , m a l e s l o s t t h e i r s i t e a t t a c h m e n t and a g g r e s s i v e t e n d e n c i e s and formed m u t u a l l y t o l e r a n t s o c i a l a g g r e g a t i o n s ( P a j u n e n , 1966a). E n v i r o n m e n t a l f a c t o r s s u c h as a i r t e m p e r a t u r e and p r e c i p i t a t i o n a l s o i n f l u e n c e t e r r i t o r i a l a g g r e s s i o n . T e r r i t o r i a l m a l e s s t o p f l y i n g d u r i n g c o o l , c l o u d y o r r a i n y i n t e r v a l s , a l t h o u g h f e m a l e s , w h i c h a r e not a g g r e s s i v e , c o n t i n u e t o f l y d u r i n g c l o u d y p e r i o d s ( P a j u n e n , 1966b). A g g r e s s i v e i n t e n s i t y (and m a t i n g f r e q u e n c y ) i n c r e a s e s a f t e r p e r i o d s o f bad weather (Moore, 1952). L e s s work has been done on l e p i d o p t e r a n t e r r i t o r i a l i t y , b u t s t u d i e s i n d i c a t e t h a t l e p i d o p t e r a n m a l e s , l i k e t h e i r o d o n a t e c o u n t e r p a r t s , d e f e n d " f e m a l e s e a r c h a r e a s " ( B a k e r , 1972). B o t h Baker (op. c i t . ) and W e l l i n g t o n (1974a) f o u n d t h a t 9 n y m p h a l i d m a l e s e s t a b l i s h t e r r i t o r i e s i n s u n l i t a r e a s w i t h d e f i n i t e t o p o g r a p h i c a l c h a r a c t e r i s t i c s , e.g., s u n l i t a r e a s bounded by v e r t i c a l e d g e s . The g e o g r a p h i c a l l o c a t i o n of a ma l e ' s t e r r i t o r y may v a r y from day t o day ( S c o t t , 1974) or re m a i n c o n s t a n t . W e l l i n g t o n (1974a) o b s e r v e d a n y m p h a l i d male d e f e n d i n g t h e same a r e a f o r t h e same p e r i o d e a c h day, and h y p o t h e s i z e d t h a t t h e d a i l y o n s e t o f t e r r i t o r i a l b e h a v i o u r was r e l a t e d t o t h e d i s a p p e a r a n c e o f p o l a r i z e d l i g h t needed f o r n a v i g a t i o n . R e s i d e n t l e p i d o p t e r a n m a l e s behave t e r r i t o r i a l l y t o w a r d most i n t r u d e r s , i n c l u d i n g b i r d s ( P y l e , 1972, H e n d r i c k s , 1974, D a v i e s , 1978b), d r i f t i n g l e a v e s , bees and even p e o p l e ( W e l l i n g t o n , 1974a). C o n s p e c i f i c f e m a l e s a r e a p p r o a c h e d and c o u r t e d f o r 2-3 h b e f o r e c o p u l a t i o n t a k e s p l a c e . E n c o u n t e r s between c o n s p e c i f i c m ales a r e s i m i l a r t o t h o s e between o d o n a t e m a l e s , e x c e p t t h a t t h e s p i r a l l i n g p a i r g a i n h e i g h t a s e a c h male t r i e s t o a c h i e v e and m a i n t a i n a p o s i t i o n s l i g h t l y b e h i n d and above t h e o t h e r ( B a k e r , 1972). T e r r i t o r i a l b e h a v i o u r among o r t h o p t e r a n m a l e s i s o f t e n r e l a t e d t o a s o c i a l h i e r a r c h y . Ewing (1972, 1973) r e c o g n i z e d t h r e e c a t e g o r i e s of t e r r i t o r i a l c o c k r o a c h m a l e s : a l p h a , b e t a and gamma. A l p h a males were t h e t o p - r a n k i n g m a l e s , b e t a s s u b o r d i n a t e t o a l p h a s , and gammas s u b m i s s i v e t o b o t h a l p h a s and b e t a s . A gamma's p r e s e n c e was o f t e n t o l e r a t e d by t e r r i t o r i a l a l p h a s and b e t a s w h i c h would n o t p e r m i t males of t h e i r own rank on t h e i r t e r r i t o r i e s . The d i s t i n c t i o n between t h e t h r e e r a n k s was not r e a d i l y a p p a r e n t a t low d e n s i t i e s when t h e r e was a 10 s u r f e i t o f t e r r i t o r i e s , but became o b v i o u s when d e n s i t i e s i n c r e a s e d o r when f e m a l e s were p r e s e n t . B a t t l e s between m a l e s were common, and young males w h i c h f o u g h t r e p e a t e d l y and a l w a y s l o s t o f t e n d i e d of s t r e s s ( E wing, 1967). Male c r i c k e t s a r e a l s o p a r t of a s o c i a l h i e r a r c h y . E a c h male i s dominant on h i s own t e r r i t o r y but a p t t o l o s e b a t t l e s on o t h e r s ' t e r r i t o r i e s . I n t e n s i t y o f a g g r e s s i v e e n c o u n t e r s i s h i g h among t o p - r a n k i n g males but l e s s e n s g r a d u a l l y t o w a r d s t h e b o t t o m of t h e h i e r a r c h y , whereas t h e f r e q u e n c y of homosexual e n c o u n t e r s i n c r e a s e s ( A l e x a n d e r , 1961). Male c r i c k e t s ( o p . c i t . ) and g r a s s h o p p e r s ( O t t e and J o e r n , 1975, S c h o w a l t e r and W h i t f o r d , 1979) b o t h s t r i d u l a t e t o a t t r a c t f e m a l e s and t o r e p e l o t h e r i n t r u d e r s . T e r r i t o r i a l male g r a s s h o p p e r s a l s o d e f e n d t e r r i t o r i e s a g a i n s t male c o n s p e c i f i c s , a l t h o u g h dominance h i e r a r c h i e s a r e not a p p a r e n t . H ymenopterans, p a r t i c u l a r l y b e e s , a r e now among t h e b e s t s t u d i e d o f t e r r i t o r i a l i n s e c t s ( E i c k w o r t and G i n s b e r g , 1980). M a l e s s e a r c h f o r f e m a l e s a t n e s t s i t e s , f l o w e r s , o r a t s i t e s t h a t l a c k a f e m a l e - a t t r a c t i n g r e s o u r c e , where f e m a l e s go o n l y t o mate o r r e s t . M a l e s s t a t i o n e d a t t h e l a t t e r k i n d of s i t e may e m i t f e m a l e - a t t r a c t i n g pheromones (op. c i t . ) . Not a l l f e m a l e -s e e k i n g m a l e s a r e t e r r i t o r i a l - some p a t r o l t h e i r c h o s e n e n c o u n t e r s i t e s n o n - a g g r e s s i v e l y and a l l o w o t h e r m a l e s t o do t h e same. But A l c o c k e t a l . (1978) l i s t e d 20 s p e c i e s of bees i n 12 g e n e r a , r e p r e s e n t i n g 6 f a m i l i e s , i n w h i c h males a r e t e r r i t o r i a l . D e t a i l e d work has been done on s p e c i e s from s e v e r a l bee and wasp f a m i l i e s : M e g a c h i l i d a e (Raw, 1975a, . 1 1 J a y c o x , 1967, Pechuman, 1967, E i c k w o r t , 1977, W a i n w r i g h t , 1978, S e v e r i n g h a u s e t a l . , 1981), A n d r e n i d a e ( C a z i e r and L i n s l e y , 1963), A n t h o p h o r i d a e (Raw, 1975b, W a i n w r i g h t , 1978), H a l i c t i d a e ( B a r r o w s , 1976), S p h e c i d a e ( L i n , 1963, A l c o c k , 1975, C o l v i l l e and C o l v i l l e , 1980, Gwynne and 0 ' N e i l l , 1980), S c e l i o n i d a e and P t e r o m a l i d a e ( W i l s o n , 1961). T e r r i t o r i a l m a l e s a r e n o t c o n t i n u a l l y a g g r e s s i v e . F o r example, P r o t o x e a g l o r i o s a ( F o x ) , r e s t communally a f t e r a m o r n i n g ' s t e r r i t o r i a l a c t i v i t y b u t , when t e r r i t o r i a l , a l l m a i n t a i n t h e i r t e r r i t o r i e s by u s i n g p h y s i c a l d e f e n s e . S e v e r a l w o r k e r s have n o t e d t h a t , when s e a r c h i n g f o r f e m a l e s , m a l e s w i l l a p p r o a c h and pounce on a wide v a r i e t y o f i n s e c t s and o t h e r o b j e c t s o f a p p r o p r i a t e s i z e and shape ( s e e E i c k w o r t and G i n s b e r g , 1980). Female v i s u a l c u e s a r e a p p a r e n t l y i m p o r t a n t i n r e c o g n i t i o n from a d i s t a n c e , whereas c l o s e - r a n g e d i s c r i m i n a t i o n a p p e a r s t o be m o s t l y o l f a c t o r y (op. c i t . ) . T h e r e i s some e v i d e n c e f o r t e r r i t o r i a l i t y among h e m i p t e r a n m a l e s . F u j i s a k i (1980) r e p o r t e d t h a t m a l e s o f t h e w i n t e r c h e r r y bug, A n t h o c o r i s s o r d i d u s T h u n b e r g ( C o r e i d a e ) , " v i e w i t h one a n o t h e r " t o o c c u p y m i d d l e or l o w e r stems of h o s t p l a n t s where f e m a l e s t e n d t o c o n g r e g a t e . J a n n s o n (1973) n o t e d s t r i d u l a t i o n by males i n t h e genus C e n o c o r i x a ( C o r i x i d a e ) i s p a r t of an a g o n i s t i c b e h a v i o u r r e g i m e w h i c h i n c l u d e s n u d g i n g and c h a s i n g . S t r i d u l a t i o n may be a d e t e r m i n i n g f a c t o r i n s p a c i n g i n d i v i d u a l s , and i s a l s o a p r e c o p u l a t o r y s i g n a l t o r e c e p t i v e f e m a l e s . G e r r i s m a l e s ( G e r r i d a e ) a r e a b l e t o a t t r a c t r e c e p t i v e f e m a l e s and p e r h a p s t o i n d u c e o v i p o s i t i o n u s i n g h i g h 12 f r e q u e n c y s u r f a c e wave c o m m u n i c a t i o n ( W i l c o x , 1979); t h e s e s e x -s p e c i f i c s i g n a l s may a l s o p l a y a p a r t i n t e r r i t o r i a l and s p a c i n g b e h a v i o u r ( R o l l o , p e r s . comm., 1978). T h e r e i s o n l y one r e p o r t e d i n s t a n c e of t e r r i t o r i a l i t y i n th e C o l e o p t e r a ( R i c h a r d s , 1980). M a l e s of t h e c o c c i n e l l i d , L e p t o t h e a g a l b u l a ( M u l s a n t ) , g u a r d q u i e s c e n t f e m a l e pupae prior:, t o emergence and e a c h male mates w i t h h i s g u a r d e d f e m a l e a f t e r she emerges. M a l e t e r r i t o r i a l i t y i s r e c o g n i z e d among f o u r f a m i l i e s of d i p t e r a n s : t h e G a s t r o p h i l i d a e , t h e D r o s o p h i l i d a e , t h e T e p h r i t i d a e and t h e S y r p h i d a e . A l t h o u g h males of some o t h e r f a m i l i e s ( e . g . , S c a t o p h a g a s t e r c o r a r i a ) s e a r c h f o r r e c e p t i v e f e m a l e s , t h e y n e i t h e r d e f e n d a p a r t i c u l a r l o c a t i o n n o r a " f l o a t i n g " t e r r i t o r y , and a r e t h e r e f o r e n ot c l a s s i f i e d t e r r i t o r i a l ( P a r k e r , 1970a,b). G a s t r o p h i l u s i n t e s t i n a l i s m a l e s d e f e n d h o s t - s i t e s ( h o r s e s ) or s i t e s a t h i l l t o p s ( C a t t s , 1979). A t h i l l t o p s i t e s , m a l e s h o v e r a t a p p r o x i m a t e l y 20 cm above t h e g r o u n d and p u r s u e most i n t r u d e r s . A l l p u r s u i t s b e g i n t h e same way: t h e r e s i d e n t f l i e s a f t e r t h e i n t r u d e r and c o n t a c t s i t . I f t h e i n t r u d e r i s n o t a c o n s p e c i f i c f e m a l e , t h e p a i r may s p i r a l as h i g h a s 3 m b e f o r e f a l l i n g t o t h e g r o u n d and s e p a r a t i n g ; i f f e m a l e , c o n t a c t i s f o l l o w e d by a 3-4 min c o p u l a t i o n on t h e g r o u n d . M a l e s c o n t i n u e t o h o v e r as l o n g a s t h e t e m p e r a t u r e a t h o v e r i n g h e i g h t i s between 19 and 34°C, even i n winds of 15-20 km/h. They f a c e t h e wind, c o u r s i n g back and f o r t h i n a h o r i z o n t a l a r c o f <1 m. D u r i n g warm w e a t h e r , m a l e s may h o v e r f o r 30 min a t a t i m e , but 13 when t e m p e r a t u r e s a r e c o o l o r m a l e s a r e o l d , t h e y s i t f o r l o n g e r p e r i o d s t h a n t h e y h o v e r . Most d r o s o p h i l i d m a l e s a r e n o t t e r r i t o r i a l . I n s t e a d o f a c t i n g a g g r e s s i v e l y a t o v i p o s i t i o n s i t e s , a male a s c e r t a i n s t h e sex and r e c e p t i v i t y of d r o s o p h i l i d s a t t h e s i t e by g e n t l y t a p p i n g any i n d i v i d u a l t h a t i s a p p r o x i m a t e l y t h e same s i z e as a f e m a l e D r o s o p h i l a . I f t h e i n d i v i d u a l i s a v i r g i n f e m a l e , t h e male c o n t i n u e s h i s c o u r t s h i p ; i f n o t , he t u r n s away w i t h o u t d i s p l a y i n g any a g g r e s s i v e b e h a v i o u r ( S p i e t h , 1968). But m a l e s of s e v e r a l H a w a i i a n D r o s o p h i l a s p e c i e s a r e d e f i n i t e l y t e r r i t o r i a l ( op. c i t . ) . A t a f e e d i n g s i t e , b o t h m a l e s and f e m a l e s r e s t r i c t t h e i r a c t i v i t i e s t o f e e d i n g ; t h o u g h f e m a l e s may o v i p o s i t t h e r e as w e l l , m ales show no a g g r e s s i v e t e n d e n c i e s . As soon as males l e a v e t h e s i t e and f l y t o s u r r o u n d i n g v e g e t a t i o n , however, t h e y become h i g h l y i n t o l e r a n t of i n d i v i d u a l s i n c l o s e p r o x i m i t y . M a l e s spend much l e s s t i m e f e e d i n g t h a n f e m a l e s , and t h e r e f o r e s pend a g r e a t p r o p o r t i o n of t h e i r t i m e away from f e e d i n g s i t e s . They a r e f o u n d s i t t i n g on l e a f s u r f a c e s , f e r n f r o n d s t i p e s and t r e e t r u n k s , and o f t e n a c c u m u l a t e a t t h e s e s i t e s . E a c h male d e f e n d s a l i m i t e d a r e a : a s i n g l e l e a f , a f e r n p i n n a , a s e c t i o n of a f e r n f r o n d stem or a p o r t i o n o f a t r e e t r u n k . The t y p e o f t e r r i t o r y c h o s e n by males depends on s p e c i e s - s p e c i f i c p r e f e r e n c e s f o r l i g h t , h u m i d i t y , t e m p e r a t u r e and s p a c e . T e r r i t o r i e s a r e a l s o i n v a r i a b l y e s t a b l i s h e d n e a r f e e d i n g and o v i p o s i t i o n s i t e s . T e r r i t o r i a l m ales of some s p e c i e s ( e . g . , D. c r u c i g e r a , D. g r i m s h a w i and D. e n g y o c h r a c e a ) 14 a d v e r t i s e t h e i r p r e s e n c e by d r a g g i n g t h e t i p of t h e i r abdomen o v e r t h e s u b s t r a t e , d e p o s i t i n g a t h i n f i l m of l i q u i d as t h e y do s o . O t h e r s assume a r i t u a l i z e d p o s t u r e , e x u d i n g and r e t r a c t i n g a b u b b l e o f f l u i d from t h e i r a n a l p a p i l l a e . O f t e n t h e mere a s s u m p t i o n of t h i s a g g r e s s i v e s t a n c e w i l l r e p e l i n t r u d i n g males, and n o n - r e c e p t i v e f e m a l e s : i f n o t , t h e t e r r i t o r y owner r e s p o n d s w i t h p h y s i c a l c o n t a c t , s l a s h i n g a t i n t r u d e r s w i t h h i s wings and l e g s . B e c a u s e c o u r t s h i p s i t e s a r e s p a t i a l l y s e p a r a t e d from s i t e s of f e e d i n g and o v i p o s i t i o n , m a l e s must a t t r a c t r e c e p t i v e f e m a l e s t o t h e i r t e r r i t o r i e s . S p i e t h (1968) p o s t u l a t e d t h a t l e k b e h a v i o u r has e v o l v e d i n H a w a i i a n D r o s o p h i l a f o r t h i s r e a s o n . T r u e l e k b e h a v i o u r " i n v o l v e s a number of p r o m i s c u o u s males a s s e m b l i n g i n c l o s e p r o x i m i t y and e n g a g i n g i n s t r i k i n g l y h y p e r t r o p h i e d d i s p l a y s w h i c h a t t r a c t s e x u a l l y m ature and r e c e p t i v e f e m a l e s t o communal f e e d i n g g r o u n d s " (op. c i t . ) . He s u g g e s t e d t h a t l e k b e h a v i o u r i s an a d v a n t a g e t o t h e s p e c i e s . "The d r o s o p h i l i d p a t t e r n a l l o w s t h e f e m a l e t o p r o c e e d w i t h h e r i m p o r t a n t t a s k s of f e e d i n g and o v i p o s i t i n g , w i t h o u t t h e k i n d s of p h y s i c a l h a r a s s m e n t t h a t would p e r t a i n i f t h e most p r i m i t i v e p a t t e r n of t h e m a l e - l u n g i n g - o n t o - t h e - f e m a l e p e r t a i n e d . " M a l e s o f some s p e c i e s o f t e p h r i t i d s d e f e n d f i x e d - s p a c e t e r r i t o r i e s , whereas o t h e r s m a i n t a i n f l o a t i n g , " p e r s o n a l s p a c e " t e r r i t o r i e s . M a l e s o f a t l e a s t two s p e c i e s : R h a g o l e t i s  c o m p l e t a , t h e w a l n u t husk f l y ( B o y c e , 1934; i n B i g g s , 1972) and R. i n d i f f e r e n s , t h e w e s t e r n c h e r r y f r u i t f l y ( A l i N i a z e e , 1974) d e f e n d t e r r i t o r i e s of t h e f i r s t t y p e . A t e r r i t o r i a l male w a l n u t 15 husk f l y " . . . w a l k s s p r y l y a b o u t , w i t h wings e x t e n d e d upward and o u t w a r d , moving them by sudden j e r k s much a f t e r t h e f a s h i o n of a s t r u t t i n g p e a c o c k " ( B o y c e , 1934; i n B i g g s , 1972). I f a n o t h e r male f l y a p p r o a c h e s , e i t h e r t h e r e s i d e n t male c h a r g e s him or b o t h f l i e s a p p r o a c h e a c h o t h e r , r e a r up, and g r a p p l e v e n t e r t o v e n t e r . U n l e s s b o t h f l i e s f a l l o f f t h e n u t , combat c o n t i n u e s u n t i l one i s d i s l o d g e d , c r o u c h e s i n a d e f e a t e d p o s i t i o n , or f l i e s away. T e r r i t o r i a l b e h a v i o u r of t h e c h e r r y f r u i t f l y t o w a r d s o t h e r m a l e s f o l l o w s a s i m i l a r p a t t e r n ( A l i N i a z e e , 1974). The b e h a v i o u r of a male c h e r r y f r u i t f l y t o w a r d s i n t r u d i n g f e m a l e s i s d i f f e r e n t t h a n h i s r e s p o n s e t o o t h e r m a l e s , however (op. c i t . ) . A p p a r e n t l y , a f e m a l e ' s b e h a v i o u r d i s t i n g u i s h e s h e r f rom a male; a t e r r i t o r i a l r e s i d e n t does not behave a g g r e s s i v e l y t o w a r d f e m a l e s but manoeuvers h i m s e l f i n t o a p o s i t i o n t h a t w i l l f a c i l i t a t e a q u i c k m a t i n g jump o n t o t h e f e m a l e . Sometimes t h i s b e h a v i o u r i s o b s e r v e d when a r e s i d e n t a p p r o a c h e s an i n t r u d i n g male, i n d i c a t i n g t h a t n o n - a g g r e s s i v e m a l e s may be m i s t a k e n f o r f e m a l e s (op. c i t . ) . A l i N i a z e e (op. c i t . ) o b s e r v e d a g g r e s s i v e b e h a v i o u r i n young R. i n d i f f e r e n s f e m a l e s . They were o f t e n seen f i g h t i n g b o t h m a l e s and f e m a l e s , a l t h o u g h f i g h t s between f e m a l e s were not as v i g o r o u s as t h o s e between m a l e s . However, f e m a l e a g g r e s s i o n was o n l y o b s e r v e d i n t h e l a b o r a t o r y , where i n s e c t d e n s i t y was g r e a t e r t h a n i t n o r m a l l y i s i n t h e f i e l d . M ale t e r r i t o r i a l b e h a v i o u r a l s o s u b s i d e d under l a b o r a t o r y c o n d i t i o n s : one male would t o l e r a t e a n o t h e r on t h e same c h e r r y 16 w i t h o u t i n i t i a t i n g an a g g r e s s i v e e n c o u n t e r . A g g r e s s i v e d i s p l a y s o c c u r r e d o n l y when males got v e r y c l o s e t o e a c h o t h e r , i n d i c a t i n g t h a t a t h i g h d e n s i t i e s , t e r r i t o r i a l b o u n d a r i e s became so r e d u c e d t h a t m a l e s d e f e n d e d o n l y s m a l l , p e r s o n a l -s p a c e t e r r i t o r i e s . R. p o m o n e l l a , t h e a p p l e maggot, a p p a r e n t l y d e f e n d s o n l y a p e r s o n a l - s p a c e t e r r i t o r y , not a s p a t i a l l y - f i x e d one ( B i g g s , 1972). M a l e s ' a g g r e s s i v e d i s p l a y s c o n s i s t of w i n g - w a v i n g , c h a r g i n g , and pawing w i t h p r o t h o r a c i c l e g s . F e m a l e s a l s o behave a g g r e s s i v e l y , c h a r g i n g and waving t h e i r wings a t o t h e r i n d i v i d u a l s . Female a g g r e s s i o n seems p r i m a r i l y a s s o c i a t e d w i t h n o n - r e c e p t i v i t y . P r o k o p y and Bush (1973) o b s e r v e d t h a t a g g r e s s i v e b e h a v i o u r was most common among f e m a l e s not engaged i n o v i p o s i t i o n a c t i v i t y . I f a f e m a l e e n c o u n t e r e d a male on t h e s u r f a c e o f a f r u i t , she e i t h e r f l e w away, r e a c t e d p a s s i v e l y ( a p p a r e n t l y i g n o r i n g t h e m a l e ) , o r r e a c t e d i n an a g g r e s s i v e manner, u s i n g h e r wings and moving i n s h o r t c h a r g e s t o w a r d s t h e m a l e . T h i s t y p e of b e h a v i o u r was not r e s t r i c t e d t o e n c o u n t e r s w i t h m a l e s ; P r o k o p y and Bush (op. c i t . ) o b s e r v e d f e m a l e s r e a c t i n g a g g r e s s i v e l y t o o t h e r f e m a l e s , or even t o i n a n i m a t e o b j e c t s s u c h as i n s e c t f r a s s , b i r d dung, o r t h e c a l y x of an a p p l e . Female a g g r e s s i o n may have e v o l v e d b e c a u s e m a l e s a r e u n a b l e t o d i s t i n g u i s h between t h e s e x e s u n t i l t h e s t a g e of t a c t i l e c o n t a c t , and p r o b a b l y c a n n o t d i s t i n g u i s h n o n - r e c e p t i v e from r e c e p t i v e f e m a l e s e x c e p t by b e h a v i o u r (op. c i t . ) . The r e a c t i o n of f e m a l e s t o w a r d i n a n i m a t e o b j e c t s may be an a g g r e s s i o n - r e l e a s i n g mechanism s i m i l a r t o t h a t o b s e r v e d i n 17 t e r r i t o r i a l m a l e s of o t h e r o r d e r s ( e . g . , n y m p h a l i d b u t t e r f l i e s ) w h i c h r e s p o n d a g g r e s s i v e l y t o d r i f t i n g l e a v e s . . T h e r e i s some e v i d e n c e t h a t , i n R. p o m o n e l l a , sex r e c o g n i t i o n may a l s o be i n f l u e n c e d by c h e m i c a l c u e s . P r o k o p y and Bush ( 1 9 7 2 ) ' d i s c o v e r e d t h a t b o t h s e x e s d e p o s i t an u n i d e n t i f i e d c h e m i c a l . o n t h e f r u i t w h i c h , upon t a c t i l e c o n t a c t a c t s as a m a l e - a r r e s t i n g s u b s t a n c e . When d e p o s i t e d by f e m a l e s , t h i s s u b s t a n c e may s t i m u l a t e s e x u a l a g g r e s s i v e n e s s i n m a l e s ; when d e p o s i t e d by m a l e s , i t may i n c r e a s e f e m a l e r e c e p t i v i t y d u r i n g c o p u l a t i o n a t t e m p t s . The c h e m i c a l may a l s o s t i m u l a t e t h e a g g r e g a t i o n of g r o u p s of m a l e s ( l e k s ) o b s e r v e d by S m i t h and P r o k o p y ( 1 9 8 0 ) . A l t h o u g h s y r p h i d t e r r i t o r i a l i t y has o n l y r e c e n t l y a t t r a c t e d t h e a t t e n t i o n of e n t o m o l o g i s t s , i t i s more w i d e s p r e a d t h a n p r e v i o u s l y b e l i e v e d . To d a t e , t h e r e a r e o n l y a few p a p e r s on t e r r i t o r i a l i t y i n s y r p h i d s , i n c l u d i n g C o l l e t t and Land ( 1 9 7 5 ) , W e l l i n g t o n (1976) and M a i e r and Waldbauer ( 1 9 7 9 ) . P a r m e n t e r (1944, i n M a i e r and Wa l d b a u e r , 1979) o b s e r v e d p a t r o l l i n g S y r i t t a p i p l u s ( L . ) m a l e s c h a s i n g c o n s p e c i f i c and o t h e r i n s e c t s away from f l o w e r s , and h y p o t h e s i z e d t h a t t h i s c o n s t i t u t e d t e r r i t o r i a l b e h a v i o u r . S t a t i o n - k e e p i n g - i n w h i c h m a l e s h o v e r a l o n e or i n g r o u p s , p u r s u e p a s s e r s b y and t h e n r e t u r n t o t h e o r i g i n a l h o v e r i n g s p o t - has been o b s e r v e d i n t h e M i l e s i i n a e [ e . g . , E r i s t a l i s ( C o l l e t t and Land, 1975), V o l u c e l l a ( B l i c k l e , 1959)] and i n t h e S y r p h i n a e [ e . g . , M e l anostoma ( G r u h l , 1924, i n M a i e r and Waldbauer, 1979), S y r p h u s ( H e i n r i c h and P a n t l e , 1975) ] . 18 W e l l i n g t o n (1976) r e c o g n i z e d t e r r i t o r i a l i t y i n m a l e s of E r i s t a l i s t e n a x and Merodon e q u e s t r i s . E . t e n a x m a l e s d e f e n d 1-2 m t e r r i t o r i e s , d i v i d i n g t h e i r t i m e between s h o r t f l i g h t s and r e s t s w i t h i n t h e t e r r i t o r y , and l o n g e r f l i g h t s t o n e u t r a l f e e d i n g o r g r o o m i n g s t a t i o n s s e v e r a l m beyond t h e t e r r i t o r y . M a l e s of t h e mid-summer g e n e r a t i o n r e t u r n d a i l y t o t h e same t e r r i t o r y , but t h o s e of t h e autumn g e n e r a t i o n a r e n o t t e r r i t o r i a l . M. e q u e s t r i s , t h e n a r c i s s u s b u l b f l y , i s a l s o h i g h l y t e r r i t o r i a l , and i s o f t e n so a g g r e s s i v e t o w a r d s f o r a g i n g h o n e y b e e s and m e g a c h i l i d s t h a t t h o s e i n s e c t s l e a r n t o a v o i d b u l b - f l y t e r r i t o r i e s (op. c i t . ) . M a i e r and Waldbauer (1979) s t u d i e d t e r r i t o r i a l i t y among many s p e c i e s of s y r p h i d s , p r i n c i p a l l y M a l l o t a b a u t i a s ( W a l k e r ) , M a l l o t a b o s t i c a ( F . ) , Somi11a d e c o r a M a c q u a r t and S p i l o m y i a  h o m i f e r a Loew. A l l a r e u n i v o l t i n e and, i n I l l i n o i s ( t h e s i t e of t h e i r s t u d y ) , f l y d u r i n g May, June and e a r l y J u l y . In t h e m o r n i n g , t h e y f e e d and mate a t f l o w e r s w h i c h grow n e a r f o r e s t s . In t h e a f t e r n o o n , m ales w a i t n e a r l a r v a l h a b i t a t s i n t h e f o r e s t t o mate w i t h f e m a l e s a r r i v i n g t o o v i p o s i t . F e m a l e s a r e a p p a r e n t l y c o n t i n u a l l y r e c e p t i v e o r u n r e c e p t i v e o n l y f o r b r i e f p e r i o d s . They a l s o spend a l a r g e r p r o p o r t i o n of t h e i r t i m e f e e d i n g t h a n m a l e s . In t h e m o r n i n g , males of a l l f o u r s p e c i e s p a t r o l f l o w e r i n g p l a n t s , s e a r c h i n g f o r f e m a l e s . M. b a u t i a s , M. p o s t i c a t a , and S. d e c o r a e a c h p a t r o l f l o w e r s of 10-20 p l a n t s w i t h i n a 50 m d i s t a n c e ; S. h a m i f e r a males p a t r o l s m a l l e r a r e a s and a r e g e n e r a l l y more s e d e n t a r y . M a l e s of a l l f o u r s p e c i e s p a t r o l t h e 19 same f l i g h t p a t t e r n r e p e a t e d l y . F l i g h t c o u r s e s of i n d i v i d u a l s o f t e n o v e r l a p a l t h o u g h m a l e s a r e u s u a l l y s p a t i a l l y s e p a r a t e d a t a g i v e n moment. When c o n s p e c i f i c m a l e s come i n t o c l o s e p r o x i m i t y , one p u r s u e s t h e o t h e r i n . a h i g h - s p e e d c h a s e , w h i c h u s u a l l y l a s t s no l o n g e r t h a n 5 s and doe s not i n v o l v e p h y s i c a l c o n t a c t . One male, u s u a l l y t h e p u r s u e r , r e t u r n s t o t h e s i t e of t h e e n c o u n t e r and c o n t i n u e s p a t r o l l i n g . M a l e s f e e d i n g o r r e s t i n g on f o l i a g e o f t e n r e a c t t h e same way t o an i n t r u d e r . In t h e a f t e r n o o n , M. p o s t i e a t a and S. d e c o r a males seek f e m a l e s i n t h e f o r e s t n e a r t h e i r r e s p e c t i v e l a r v a l h a b i t a t s , as w e l l a s a t f l o w e r s o u t s i d e t h e f o r e s t . I n d i v i d u a l M. p o s t i e a t a m a l e s d e f e n d n e a r l y c i r c u l a r m a t i n g t e r r i t o r i e s , 1-2 m i n d i a m e t e r , a r o u n d wet, d e t r i t u s - f i l l e d p o c k e t s i n t r e e s . T h e s e r o t p o c k e t s n e a r l y a l w a y s have c i r c u l a r o p e n i n g s . S. d e c o r a m a l e s d e f e n d s i m i l a r l y - s i z e d o p e n i n g s n e a r d r i e r d e t r i t u s - f i l l e d h o l e s w i t h e l o n g a t e o p e n i n g s . M a l e s of b o t h s p e c i e s p r e f e r p e r c h e s on l e a v e s or t r e e t r u n k s n e a r t h e t r e e h o l e e n t r a n c e w h i c h a f f o r d an u n o b s t r u c t e d view of f e m a l e s a r r i v i n g t o o v i p o s i t . M a l e s c h a s e c o n s p e c i f i c males and o t h e r i n s e c t s which p a s s n e a r t h e t r e e h o l e e n t r a n c e , and a l s o make s p o n t a n e o u s f l i g h t s ( i . e . , f l i g h t s n o t t r i g g e r e d by p a s s i n g i n s e c t s ) . Between r e s t s and b u r s t s o f f l i g h t a c t i v i t y , m a l e s h o v e r a t t h e t r e e h o l e o p e n i n g and f l y a b o u t t h e t e r r i t o r y . M. p o s t i c a t a m ales a r e a p p a r e n t l y c a p a b l e of s t i m u l u s -f i l t e r i n g ; M a i e r and Waldbauer (1979) o b s e r v e d t h a t t h e y r a r e l y p u r s u e d i n s e c t s s m a l l e r t h a n t h e m s e l v e s , but p u r s u e d 80% o f p a s s i n g i n s e c t s t h a t were t h e same s i z e or l a r g e r . S. d e c o r a 20 m a l e s a r e l e s s d i s c i m i n a t i n g . P u r s u i t s by males o f b o t h s p e c i e s o f t e n i n c l u d e p h y s i c a l c o n t a c t and, l e s s f r e q u e n t l y , h e a d - t o -head c o n t a c t . B o t h w i l l a l s o r e a c t t o wind-blown l e a v e s and , o t h e r moving i n a n i m a t e o b j e c t s . M. p o s t i c a t a m a l e s a r e a p p a r e n t l y u n a b l e t o d i s c r i m i n a t e between t h e s e x e s . M a i e r and Waldbauer (1979) r e p o r t e d t h a t a t e r r i t o r i a l male would a t t e m p t t o mate w i t h d ead or l i v e c o n s p e c i f i c s o f e i t h e r s e x . M a l e s h o l d i n g h i g h - q u a l i t y t e r r i t o r i e s n e a r r o t c a v i t i e s s h o u l d have a h i g h e r f i t n e s s t h a n o t h e r males (op. c i t . ) . I f f e m a l e s y r p h i d s , l i k e c y c l o r r h a p o u s d i p t e r a n f e m a l e s , have t h e m a j o r i t y of eggs f e r t i l i z e d by sperm o b t a i n e d i n t h e i r l a s t m a t i n g ( P a r k e r , 1970c) and i f , a s p r o p o s e d by M a i e r and Waldbauer, s y r p h i d f e m a l e s a r e a l m o s t c o n t i n u a l l y r e c e p t i v e , t h e n m a l e s h o l d i n g h i g h - q u a l i t y t e r r i t o r i e s s h o u l d be t h e l a s t t o mate w i t h f e m a l e s t h a t a p p r o a c h t h e t r e e h o l e i n o r d e r t o o v i p o s i t . M a l e s t h a t p a t r o l f l o w e r s , e s p e c i a l l y i n t h e a f t e r n o o n , a r e not a u t o m a t i c a l l y r e l e g a t e d t o l o w e r f i t n e s s , however. Some f e m a l e s mated a t f l o w e r s i n t h e m o r n i n g may o v i p o s i t i n r o t c a v i t i e s i n t h e m o r n i n g when no m a l e s a r e d e f e n d i n g o v i p o s i t i o n s i t e s . F e m a l e s mated a t f l o w e r s i n t h e a f t e r n o o n may o v i p o s i t i n an u n d e f e n d e d t r e e c a v i t y . M a i e r and Waldbauer n o t e d t h a t a l t h o u g h some m a l e s d e f e n d o n l y f l o w e r s o r o v i p o s i t i o n s i t e s i n t h e i r l i f e t i m e , some d e f i n i t e l y do b o t h and by d o i n g s o , may maximize t h e i r p o t e n t i a l f i t n e s s and g a i n a d i s t i n c t s e l e c t i v e a d v a n t a g e . M a i e r and Waldbauer a l s o p o i n t e d o u t t h a t s i m i l a r d u a l m a t e - s e e k i n g s t r a t e g i e s e x i s t i n t e r r i t o r i a l male b e e s , e.g., 21 i n t h e a n t h o p h o r i d C e n t r i s p a l l i d a Fox ( A l c o c k , 1976) and i n t h e m e g a c h i l i d Osmia r u f a ( L . ) (Raw, 1975a). " P a r a l l e l s i n bee and s y r p h i d e c o l o g y may be l a r g e l y r e s p o n s i b l e f o r t h e e v o l u t i o n o f d u a l m a t e - s e e k i n g s t r a t e g i e s , p a r t i c u l a r l y b e h a v i o u r . ... B o t h bees and s y r p h i d s e x p l o i t two w e l l - d e f i n e d r e s o u r c e s : f l o w e r s . f o r p o l l e n and n e c t a r , and s i t e s f o r l a r v a l d e v e l o p m e n t ( o r n e s t s i n b e e s ) . S i n c e f e m a l e s u t i l i z e t h e s e r e s o u r c e a r e a s , m a l e s t h a t s e a r c h o r w a i t t h e r e p r o b a b l y have i n c r e a s e d m a t i n g s u c c e s s " ( M a i e r and Waldbauer, 1979). 22 MATERIALS AND METHODS The t h r e e s p e c i e s of s y r p h i d s were o b s e r v e d a t two s t u d y s i t e s : a V a n c o u v e r g a r d e n and a f i e l d p l o t a t t h e U n i v e r s i t y of B r i t i s h C o l u m b i a . M a l e s of a l l t h r e e s p e c i e s were p r e s e n t i n t h e g a r d e n , b ut o n l y E r i s t a l i s t e n a x i n d i v i d u a l s were f o u n d a t th e f i e l d p l o t . . The o b s e r v a t i o n p e r i o d began on May 7, 1980 and c o n t i n u e d , w e ather p e r m i t t i n g , u n t i l A u g u s t 25, 1980. The 1981 f i e l d s e a s o n was c u t s h o r t by i n c l e m e n t w e a t h e r , and t h e r e f o r e i n c l u d e d o n l y t h r e e d a y s i n May and one i n J u n e . I o b s e r v e d t e r r i t o r i a l b e h a v i o u r among m a l e s of t h e one (and o n l y ) g e n e r a t i o n o f Merodon e q u e s t r i s , and of two o r t h r e e g e n e r a t i o n s of Eumerus t u b e r c u l a t u s , but o f o n l y t h e f i r s t (summer) g e n e r a t i o n o f E r i s t a l i s t e n a x . S e c o n d (autumn) g e n e r a t i o n E. t e n a x males a r e n o t t e r r i t o r i a l ( W e l l i n g t o n , 1976). O b s e r v a t i o n s from t h e f a l l of 1980 s u p p o r t W e l l i n g t o n ' s c o n c l u s i o n . T w e n t y - s e v e n M. e q u e s t r i s , 30 E . t u b e r c u l a t u s and >50 E. t e n a x m a l e s were o b s e r v e d d u r i n g t h e c o u r s e o f t h e s t u d y . I n d i v i d u a l i n s e c t s were, when p o s s i b l e , marked f o r i d e n t i f i c a t i o n w i t h a s p o t of p a i n t from one of f i v e d i f f e r e n t c o l o u r e d M e t r o n m a r k i n g p e n s . I n s e c t s were not c a u g h t f o r m a r k i n g , s i n c e c a p t u r e i n v a r i a b l y u p s e t them and c a u s e d them t o l e a v e t h e a r e a ( a l s o see S i n g e r and Wedlake, 1981). I n s t e a d , t h e y were marked as t h e y s a t g r o o m i n g , b a s k i n g o r f e e d i n g . T h i s m a r k i n g p r o c e d u r e worked w e l l on t h e two b u l b f l y s p e c i e s , but male d r o n e f l i e s were u s u a l l y t o o f l i g h t y t o be marked and, t h e r e f o r e , were i n d i v i d u a l l y i d e n t i f i e d by , d i f f e r e n c e s i n s i z e , c o l o u r and wear p a t t e r n s . [The p r o b l e m of m a r k i n g c a n n o t be s o l v e d by m a r k i n g newly-emerged m a l e s b e f o r e t h e y have e s t a b l i s h e d t e r r i t o r i e s s i n c e , l i k e most k i n d s o f i n s e c t s (Johnson,. 1969), d r o n e f l i e s b e g i n t h e i r a d u l t s t a g e w i t h a p e r i o d of o b l i g a t o r y d i s p e r s a l d u r i n g w h i c h t h e y l e a v e t h e i r p l a c e of emergence and n e v e r r e t u r n . ] U s u a l l y one, but sometimes two, o b s e r v e r s r e c o r d e d movements and b e h a v i o u r as f l i e s moved from p l a c e t o p l a c e w i t h i n t h e i r home r a n g e s . D a t a were r e c o r d e d w i t h a t a p e r e c o r d e r and a s t o p w a t c h , and o b s e r v a t i o n s were s u b s e q u e n t l y t r a n s c r i b e d o n t o d e t a i l e d maps of i n d i v i d u a l home r a n g e s and t e r r i t o r i e s . P h o t o g r a p h s u s e d t o s u p p l e m e n t t h e s e o b s e r v a t i o n s were t a k e n w i t h a Pentax E S I I camera body i n c o n j u n c t i o n w i t h a 135 mm l e n s , f o u r t o s i x e x t e n s i o n t u b e s , and t h r e e e l e c t r o n i c f l a s h u n i t s . P r e l i m i n a r y o b s e r v a t i o n s d e t e r m i n e d w h i c h b e h a v i o u r s s h o u l d be r e c o r d e d . I r e c o r d e d m u t u a l l y e x c l u s i v e b e h a v i o u r s , but d i d n o t r e c o r d d e t a i l e d movements o f wings o r l e g s u n l e s s an u n u s u a l p o s t u r e or movement o c c u r r e d . F o r example, t h e b e h a v i o u r of a male w h i c h groomed h i s head, t h e n f i r s t p a i r of l e g s , t h e n l a s t p a i r , t h e n w i ngs, was n o t e d s i m p l y as " g r o o m i n g " . D e t a i l e d movements c o u l d not be c o n s i s t e n t l y r e p o r t e d w i t h t h e r e c o r d e r and s t o p w a t c h b e c a u s e o f t h e e x t r e m e l y s h o r t d u r a t i o n of many of t h e b e h a v i o u r s ( e . g . , 1-2 s) and t h e r a p i d t r a n s i t i o n s between them. Many b e h a v i o u r s ( e . g . , f e e d i n g , g r o o m i n g , b a s k i n g ) o c c u r r e d whether t h e 24 r e s i d e n t was " o n - d u t y " or " o f f - d u t y " ( T a b l e I, p.25; a l s o see p . 3 9 ) . F o r example, a male f e e d i n g o f f - d u t y would n o t r e s p o n d t o i n t r u d e r s w h i c h p a s s e d w i t h i n h i s r a n g e of v i s i o n , whereas an o n - d u t y male would a l w a y s i n t e r r u p t h i s f e e d i n g b o u t s t o p u r s u e a l l i n t e r l o p e r s . Thus t h e d i s t i n c t i o n o f a r e s i d e n t ' s on- o r o f f - d u t y s t a t u s o f t e n depended on t h e p r e s e n c e of o t h e r f l y i n g i n s e c t s . When none was p r e s e n t , I t e s t e d t h e b e h a v i o u r a l s t a t u s of t h e r e s i d e n t i n q u e s t i o n by p r e s e n t i n g him w i t h a f l y model, or f l i c k e d s m a l l p e b b l e s a c r o s s h i s f i e l d of v i s i o n , and n o t e d t h e p r e s e n c e o r a b s e n c e of a r e s p o n s e . On-duty f l i e s a l w a y s r e s p o n d e d t o a p e b b l e , but u s u a l l y l e a r n e d t h a t t h e model, a f t e r one o r two p a s s e s , was not an i n s e c t and r e t r e a t e d f r o m i t . S o i l , l e a f and a i r t e m p e r a t u r e s were t a k e n w i t h a L e e d s and N o r t h r u p t e m p e r a t u r e p o t e n t i o m e t e r model #8692-2. " A i r t e m p e r a t u r e " a l w a y s r e f e r s t o t h e t e m p e r a t u r e a t a p p r o x i m a t e l y 25 cm above t h e s o i l . The p r e s e n c e o f p o l a r i z e d l i g h t was d e t e r m i n e d by c a l c u l a t i n g t h e a n g l e of s o l a r e l e v a t i o n a t 49°N l a t i t u d e ( A l t e r and Cleminshaw, 1956; A p p e n d i x I ) . B e c a u se d i f f e r e n t k i n d s o f b e h a v i o u r s t e n d e d t o o c c u r i n s e q e n c e s , I u s e d a p a t t e r n - m a t c h i n g p r o gram t o d e t e r m i n e t h e f r e q u e n c i e s of s e q u e n c e s of b e h a v i o u r s . T h i s p a t t e r n - m a t c h i n g p r o g r a m u s e d ( d e s i g n a t e d " s t r e a k " ) was r e q u e s t e d by P e t e r Cahoon and w r i t t e n by D a v i d Z i t t i n a t t h e I n s t i t u t e of A n i m a l R e s o u r c e E c o l o g y d u r i n g t h e e a r l y p a r t of 1981. The u s e r s p e c i f i e s a b e h a v i o u r p l u s t h e l e n g t h o f s e q u e n c e s of b e h a v i o u r s e n d i n g i n t h e s p e c i f i e d b e h a v i o u r , and l i s t s t h e 25 T a b l e I . B e h a v i o u r s o f m ales of t h e t h r e e s y r p h i d s p e c i e s : M. e q u e s t r i s , E. t u b e r c u l a t u s , and E. t e n a x . 26 BEHAVIOUR DESCRIPTION TYPE NAME On-duty (responsive to intruders) watch male a l e r t and crouched, on s o i l or vegetation, while watching for intruders nbask (=watch/bask) nf eed (=watch/feed) ngroom (=watch/groom) male on-duty while basking -angles body towards sun, spreads wings, and lowers body to substrate male on-duty while feeding male on-duty while grooming wings, head, and/or any pair of legs hover * inspect p a t r o l chase chase-contact male hovers; may be done while watching, or inspecting an intruder or a flower male f l i e s toward an object to examine i t ; i f a flower, he hovers i n front of i t , i f an airborne intruder, he follows or chases i t male f l i e s around t e r r i t o r y , following one of several regular s p a t i a l patterns male pursues intruder, f l y i n g behind and s l i g h t l y above i t male chases and s t r i k e s intruder; i f intruder i s female, "contact" = "clasp"; i f not, "contact" = " s t r i k e " mate male copulates with female (continued on next page) 27 BEHAVIOUR DESCRIPTION TYPE NAME Off-duty (not responsive to intruders) s i t fbask (=sit/bask) male s i t s , off-duty, anywhere on t e r r i t o r y male off-duty while basking ffeed (=sit/feed) male off-duty while feeding fgroom (=sit/groom) male off-duty while grooming goto male f l i e s from point to point on t e r r i t o r y , but remains off-duty while doing so goaway male f l i e s away from t e r r i t o r y r e s t male s i t s at an off-duty s i t e away from the t e r r i t o r y usually observed only among _E. tenax males ft* never observed among E. tuberculatus males 28 number of t i m e s t h a t e a c h u n i q u e s e q u e n c e o c c u r s . F r e q u e n c y d i s t r i b u t i o n s c o n s t r u c t e d f r o m t h e s e d a t a a r e shown i n A p p e n d i c e s I I A 1 , I I B 1 , and 11C1. A l l sequences, p r e s e n t e d i n t h e s e a p p e n d i c e s have a l e n g t h o f t h r e e b e h a v i o u r s . I c h o s e t h i s l e n g t h f o r t h e f o l l o w i n g r e a s o n s . O u t p u t f o r a s p e c i f i e d l e n g t h of two b e h a v i o u r s showed w h i c h b e h a v i o u r s c o n s i s t e n t l y p r e c e d e d t h e one I had s p e c i f i e d . However, few c o n s i s t e n t b e h a v i o u r p a t t e r n s emerged. W i t h s e q u e n c e s of t h r e e b e h a v i o u r s , I o b t a i n e d f r e q u e n c y d i s t r i b u t i o n s of s e q u e n c e s shown i n a l l n i n e a p p e n d i c e s . Such s e q u e n c e s c o n t a i n e d i n f o r m a t i o n p r e s e n t i n s e q u e n c e s of l e n g t h two, p l u s a d d i t i o n a l i n f o r m a t i o n . F o r example, i n A p p e n d i x I I A 2 , I show t h e f r e q u e n c i e s of a l l s e q u e n c e s e n d i n g i n t h e b e h a v i o u r "watch" ( d e s i g n a t e d "w"). I t i s e v i d e n t t h a t t h e b e h a v i o u r " c h a s e " ("c") p r e c e d e s "watch" a t o t a l of 29 t i m e s . T h i s i n f o r m a t i o n can a l s o be e l u c i d a t e d by r e q u e s t i n g s e q u e n c e s of l e n g t h two. But, by r e q u e s t i n g s e q u e n c e s of l e n g t h t h r e e , one c a n see t h a t t h e b e h a v i o u r "watch" p r e c e d e s t h e s e q u e n c e " c h a s e - w a t c h " 18 o u t o f 29 t i m e s , whereas t h e b e h a v i o u r " o n - d u t y b a s k " ("nb") p r e c e d e s t h e s e q u e n c e " c h a s e - w a t c h " 11 o u t of 29 t i m e s . Such a d d i t i o n a l i n f o r m a t i o n i n d i c a t e s p a t t e r n s o f t e r r i t o r i a l d e f e n s e b e h a v i o u r s . S e quences l o n g e r t h a n t h r e e b e h a v i o u r s y i e l d e d l e s s i n f o r m a t i o n a b o u t b e h a v i o u r p a t t e r n s t h a n t h a t p r o v i d e d by f r e q u e n c i e s of s e q u e n c e s of l e n g t h t h r e e . Thus, a g i v e n s e q u e n c e of l e n g t h f o u r o r f i v e o n l y o c c u r r e d f o u r t i m e s o r l e s s . F o r example, t h e f r e q u e n c y d i s t r i b u t i o n of s e q u e n c e s of 29 l e n g t h f o u r e n d i n g i n t h e b e h a v i o u r "watch" was l e s s i n f o r m a t i v e b e c a u s e e a c h o f t h e 117 s e q u e n c e s o c c u r r e d f o u r , t h r e e , two o r , most o f t e n , one t i m e s . Hence t h e s e q u e n c e l e n g t h o f t h r e e b e h a v i o u r s was s e l e c t e d , s i n c e i t o p t i m i z e d t h e e x t r a c t i o n o f i n f o r m a t i o n c o n c e r n i n g p a t t e r n s o f b e h a v i o u r s . 30 THE NARCISSUS BULB FLY, MERODON EQUESTRIS I m p o r t a n c e Merodon e q u e s t r i s a p p a r e n t l y i s a n a t i v e o f s o u t h e r n E u r o p e . I t was f i r s t r e p o r t e d i n F r a n c e i n 1738, i n B r i t a i n i n 1842, and i n t h e P a c i f i c N o r t h w e s t ( B r i t i s h C o l u m b i a ) i n 1908 ( D o u c e t t e e t a l . , 1942). M. e q u e s t r i s i s a s e r i o u s p e s t of b u l b s , of n a r c i s s u s b u l b s i n p a r t i c u l a r , but a l s o o f A m a r y l l i s , C y r t a n t h u s , E u r y c l e s , G a l t o n i a , G a l a n t h u s , H a b r a n t h u s , I r i s , L e ucojum, S c i l l a , and V a l l o t a ( W o o d v i l l e , 1970). A d u l t f e m a l e s o v i p o s i t on p l a n t f o l i a g e a t s o i l l e v e l . A f t e r h a t c h i n g , l a r v a e t u n n e l t h r o u g h t h e s o i l t o t h e b u l b , e n t e r i t , and r e m a i n w i t h i n f o r t h e r e s t of. t h e i r l a r v a l p e r i o d . They f e e d on t h e b u l b t i s s u e and, as a r e s u l t , d e s t r o y t h e b u l b . Wounds made by l a r v a e a l s o p r o v i d e e n t r y s i t e s f o r p l a n t p a t h o g e n s . (See B r o a d b e n t , 1927, Hodson, 1932, o r D o u c e t t e e t a l . , 1942.) B i o l o g y and L i f e H i s t o r y The b i o l o g y of M. e q u e s t r i s has been w e l l - s t u d i e d i n F r a n c e ( L y o n , 1973), B r i t a i n (Hodson, 1932) and B r i t i s h C o l u m b i a ( D o u c e t t e e t a l . , 1942). I t i s s i m i l a r i n a l l t h r e e r e g i o n s . A d u l t s b e g i n t o a p p e a r i n l a t e A p r i l o r e a r l y May, and c o n t i n u e e m e r g i n g u n t i l t h e end of June o r e a r l y J u l y . M a l e s emerge b e f o r e f e m a l e s but a r e s h o r t e r - l i v e d : m a l e s i n c a p t i v i t y l i v e an a v e r a g e of 11 d a y s , whereas f e m a l e s l i v e an a v e r a g e o f 17 d a y s (Hodson, 1932). B o t h males and f e m a l e s a r e r o b u s t , 31 p u b e s c e n t f l i e s a b o u t 12 mm l o n g , w h i c h s u p e r f i c i a l l y r e s e m b l e s m a l l bumble bees and o f t e n sound l i k e them ( F i g . 1 ) . T h e r e a r e s e v e r a l i n d i v i d u a l v a r i a t i o n s i n c o l o u r p a t t e r n . Some i n d i v i d u a l s a r e a l m o s t e n t i r e l y tawny o r b l a c k , w i t h r u s t y -c o l o u r e d p o s t e r i o r a b d o m i n a l segments, w h i l e o t h e r s a r e d i s t i n g u i s h e d by c o m b i n a t i o n s of s e v e r a l c i r c u m f e r e n t i a l bands of b l a c k , g r e y , tawny o r r u s t . Hodson (1932) f o u n d t h a t a l l -b l a c k i n d i v i d u a l s were i n v a r i a b l y f e m a l e . B o t h s e x e s have l a r g e r e d d i s h e y e s ; as i n most D i p t e r a , o n l y t h e e y e s o f t h e male meet i n t h e m i d d l e of t h e f a c e ( F i g . 2 ) . B o t h s e x e s of b u l b f l i e s may be d i s t i n g u i s h e d f r o m o t h e r f l i e s by a b r o a d , t o o t h -l i k e p r o c e s s on t h e u n d e r s i d e of e a c h h i n d femur ( W o o d v i l l e , 1970) . M a l e s a r e t e r r i t o r i a l ( W e l l i n g t o n , 1976) and e s t a b l i s h t e r r i t o r i e s f o r m a t i n g p u r p o s e s . M a t i n g b e g i n s when a male makes c o n t a c t w i t h a f e m a l e , c l a s p i n g h e r t h o r a x from above w i t h h i s f i r s t two p a i r s o f l e g s . T h r e e d e f i n i t e s t a g e s i n t h e m a t i n g p r o c e s s were o b s e r v e d d u r i n g my s t u d y . D u r i n g t h e f i r s t s t a g e t h e male e x t e n d s h i s p o s t e r i o r p a i r of l e g s t o l o c a t e t h e f e m a l e ' s g e n i t a l i a and, h a v i n g done so, moves back t o i n s e r t h i s own. The f e m a l e i s u s u a l l y p a s s i v e a t t h i s s t a g e , but may a t t e m p t t o shake t h e male o f f by p u s h i n g him w i t h h e r l e g s and s w a y i n g ; i f she i s s u c c e s s f u l , t h e m a t i n g a t t e m p t e n d s . S t a g e two b e g i n s w i t h t h e c o u p l i n g o f t h e g e n i t a l i a , and c o n t i n u e s f o r a p p r o x i m a t e l y 5 min. B o t h i n s e c t s a r e q u i e t and m o t i o n l e s s d u r i n g t h i s s t a g e , a l t h o u g h t h e m a l e ' s wings may v i b r a t e ( F i g . 3 a ) . The o n s e t of s t a g e t h r e e i s marked by a l o u d , h i g h - p i t c h e d 32 F i g u r e 1. Merodon e q u e s t r i s and bumblebee. (a) A marked M. e q u e s t r i s male, showing t h e b r o a d h i n d f e m o r a . (b) An u n i d e n t i f i e d bumblebee f o r c o m p a r i s i o n . 34 F i g u r e 2. M a t i n g M. e q u e s t r i s p a i r . Note t h a t t h e m a l e ' s e y e s meet i n t h e m i d d l e o f t h e f a c e , whereas t h e f e m a l e ' s a r e w i d e l y s e p a r a t e d . 35 36 whine e m i t t e d by t h e male. The whine has been r e p o r t e d by D o u c e t t e e t a l . (1942) and i s s i m i l a r i n p i t c h t o t h a t of o t h e r s y r p h i d s ( p e r s . o b s . ) . Hodson (1932) s u g g e s t e d t h a t t h e sound may be p r o d u c e d by t h e t h o r a c i c s p i r a c l e s , but O l d r o y d (1965) s u g g e s t e d t h a t i t i s p r o d u c e d by t h e h a l t e r e s . S h o r t l y a f t e r t h e b e g i n n i n g o f s t a g e t h r e e , t h e f e m a l e t r i e s t o shake o f f t h e male, w h i c h moves back and u s u a l l y f a l l s s i d e w a y s o f f t h e f e m a l e , s t i l l e m i t t i n g t h e h i g h - p i t c h e d n o i s e ( F i g . 3 b ) . S t a g e t h r e e may c o n t i n u e f o r 0.5-3.0 min, e n d i n g when t h e i n s e c t s s e p a r a t e . B o t h u s u a l l y bask and f e e d or groom f o r s e v e r a l m i n u t e s a f t e r w a r d , and e i t h e r ( b u t u s u a l l y t h e male) may c o n t i n u e t o e m i t t h e n o i s e f o r an a d d i t i o n a l 0.5-1.0 min ( p e r s . o b s . ) . A mated f e m a l e l a y s an a v e r a g e o f 40 eggs t h r o u g h o u t h e r l i f e s p a n (Hodson, 1932). Eggs a r e 1.5 mm l o n g and c h a l k w h i t e ( D o u c e t t e e t a l . , 1942). They a r e d e p o s i t e d s i n g l y a t o r j u s t below g r o u n d l e v e l , o f t e n on h o s t p l a n t f o l i a g e or l e a f b a s e s . Eggs d e p o s i t e d on t h e s o i l s u r f a c e u s u a l l y become d e s i c c a t e d and do n o t h a t c h (Hodson, 1932). V i a b l e , w e l l - p l a c e d eggs h a t c h w i t h i n 10-15 d a y s , whereupon f i r s t - i n s t a r l a r v a e move down t h r o u g h t h e s o i l t o t h e n e a r e s t b u l b (Hodson, 1932). A l a r v a e n t e r s t h r o u g h t h e b u l b ' s b a s a l p l a t e , t u n n e l s upward, and r e m a i n s i n t h e b u l b t o c o m p l e t e t h e s u b s e q u e n t two i n s t a r s . ( U s u a l l y t h e r e i s o n l y one l a r v a p e r b u l b ; on r a r e o c c a s i o n s , two or more f e m a l e s may o v i p o s i t on t h e same s i t e so t h a t t h e i r l a r v a e o c c u p y t h e same b u l b . ) T h i r d - i n s t a r l a r v a e mature by O c t o b e r ( D o u c e t t e e t a l . , 1942) and o v e r w i n t e r i n t h e b u l b s . 37 F i g u r e 3. M. e q u e s t r i s : S t a g e s i n . m a t i n g . (a) S t a g e 2: C o p u l a t i o n , showing male wirig v i b r a t i o n . (b) S t a g e 3: The f i n a l s t a g e , showing t h e f e m a l e s h a k i n g o f f t h e male. Note t h a t t h e m a l e ' s wings a r e s t i l l . 39 E a r l y i n t h e s p r i n g , t h e l a r v a e l e a v e t h e b u l b v i a t h e b a s a l p l a t e and move upward t h r o u g h t h e s o i l u n t i l t h e i r heads j u s t p r o t r u d e t h r o u g h t h e s o i l s u r f a c e . The l a r v a l s k i n h a r d e n s t o become t h e p u p a l c a s e . P u p a t i o n t a k e s from 35-60 d a y s , d e p e n d i n g on t e m p e r a t u r e ( D o u c e t t e e t a l . , 1942). A d u l t s emerge d u r i n g l a t e m o r n i n g on warm, sunny d a y s , and a r e r e a d y t o f l y a f t e r a 1-2 h p e r i o d d u r i n g w h i c h t h e wings and e x o s k e l e t o n h a r d e n (Hodson, 1932). M. e q u e s t r i s t h u s u n d e r g o e s one c o m p l e t e g e n e r a t i o n p e r y e a r . D o u c e t t e e t a l . (1942) r e p o r t e d t h a t a p p r o x i m a t e l y 20% o f t h e l a r v a e i n a g i v e n y e a r o v e r w i n t e r a s (immature) s e c o n d -i n s t a r l a r v a e and r e q u i r e an a d d i t i o n a l y e a r t o c o m p l e t e d e v e l o p m e n t . A few, i n d i v i d u a l s may r e q u i r e t h r e e y e a r s . D o u c e t t e e t a l . (1942) p o s t u l a t e d t h a t s u c h r e t a r d e d l a r v a l d e v e l o p m e n t o c c u r s i n l a r v a e h a t c h e d from eggs d e p o s i t e d l a t e i n t h e s e a s o n ; s u c h l a r v a e may be u n a b l e .to c o m p l e t e d e v e l o p m e n t i n t h e d r y i n g t i s s u e c h a r a c t e r i s t i c of mature b u l b s . R e s u l t s C h a r a c t e r i s t i c s of a T e r r i t o r y I o b s e r v e d t h a t a l l b u t one of 27 m a l e s e s t a b l i s h e d t e r r i t o r i a l b o u n d a r i e s w h i c h a p p r o x i m a t e d t h e b o u n d a r i e s of one or more of t h e t h r e e f l o w e r beds i n t h e s t u d y a r e a . (See pp.54-62 f o r a d i s c u s s i o n o f t h e e x c e p t i o n . ) F o u r t e e n males r e s t r i c t e d t h e i r t e r r i t o r i e s t o a s i n g l e f l o w e r bed, whereas 10 40 m a l e s i n c l u d e d two o f t h e t h r e e beds i n t h e i r t e r r i t o r i e s , and 3 m a l e s m a i n t a i n e d t e r r i t o r i e s t h a t i n c l u d e d p a r t s of a l l t h r e e beds ( F i g . 4 ) . Thus t e r r i t o r y s i z e s r a n g e d from 7.0 m 2 (bed 1) t o 33.5 m 2 ( t h r e e b e d s ) , w i t h a mean of 1 7 m 2 . The f l o w e r bed most f r e q u e n t l y u s e d i n . 1980 was bed 2. I t r e c e i v e d t h e most p r o l o n g e d s u n l i g h t e a c h day. In 1981, p r u n i n g on t h e s t u d y s i t e made bed 3 t h e s u n n i e s t , and i t became t h e f a v o u r e d t e r r i t o r y . The b o u n d a r i e s of a m a l e ' s t e r r i t o r y were n e v e r c o n t i g u o u s w i t h t h o s e o f h i s home r a n g e . M a l e s w i t h t e r r i t o r i e s i n two ( o r t h r e e ) of t h e beds m a i n t a i n e d two ( o r t h r e e ) t e r r i t o r i e s w i t h i n a l a r g e r home r a n g e . U s u a l l y s u c h m a l e s b e h a v e d t e r r i t o r i a l l y o n l y w i t h i n t h e f l o w e r b e d s , n o t w h i l e f l y i n g between them. (However, m a l e s d e f e n d i n g p a r t s of beds 2 and 3 r e m a i n e d t e r r i t o r i a l i n t h e 2.7-m s p a c e between t h e a d j a c e n t c o r n e r s ) . A l l m a l e s , r e g a r d l e s s o f t h e number of t e r r i t o r i e s t h e y d e f e n d e d , a l s o r e p e a t e d l y v i s i t e d p a r t i c u l a r s i t e s ( s u b s e q u e n t l y r e f e r r e d t o as " o f f - d u t y " s i t e s ) away from t h e i r t e r r i t o r i e s , where t h e y r e s t e d d u r i n g r e s p i t e s f r o m t e r r i t o r i a l d u t y ( F i g . 4 ) . Thus a l l m a l e s m a i n t a i n e d a t l e a s t one t e r r i t o r y and one o f f - d u t y s i t e w i t h i n a l a r g e r home r a n g e . In 1980, t h e f i r s t t e r r i t o r i a l male was o b s e r v e d on May 7, and t h e l a s t on J u l y 17. Peak numbers of t e r r i t o r i a l males c o i n c i d e d w i t h p e r i o d s o f sunny w e a t h e r . L e n g t h of r e s i d e n c e v a r i e d : a male u s u a l l y d e f e n d e d h i s t e r r i t o r y f o r a t l e a s t one day, u n t i l he was d r i v e n o f f by a n o t h e r male, moved on, or d i e d . S e v e r a l m ales d e f e n d e d t e r r i t o r i e s f o r as l o n g as s i x d a y s , o r r e a p p e a r e d on s u c h t e r r i t o r i e s a f t e r f o u r t o f i v e d a y s 41 F i g u r e 4. Map of t h e s t u d y s i t e , showing p o s i t i o n s o f t h e t h r e e f l o w e r b e d s . Examples of two M. e q u e s t r i s t e r r i t o r i e s a r e i n d i c a t e d by d a s h e d l i n e s , and two o f f -d u t y s i t e s a r e i n d i c a t e d by a s t e r i s k s . 42 0 2m 43 a b s e n c e due t o i n c l e m e n t w e a t h e r . A l l t e r r i t o r i e s c o n t a i n e d f o o d p l a n t s [ b u l b f l i e s w i l l f e e d on most . f l o w e r i n g g a r d e n p l a n t s (Hodson, 1 9 3 2 ) ] , b u l b o u s p l a n t s s u c h as i r i s e s and n a r c i s s u s ( o v i p o s i t i o n s i t e s ) , a r e a s o f open s o i l , and a b a c k d r o p o f v e g e t a t i o n . T e r r i t o r i a l m a l e s p o s i t i o n e d t h e m s e l v e s on t h e s o i l o r on t h e v e g e t a t i o n n o t h i g h e r t h a n 1 m. T h e r e t h e y f a c e d away from t h e v e g e t a t i v e b a c k d r o p t o w a r d an a r e a of open s p a c e , and w a t c hed f o r i n t r u d e r s ( F i g . 5 a ) . T e r r i t o r i a l B e h a v i o u r s Once I became f a m i l i a r w i t h t h e b e h a v i o u r s i n v o l v e d i n t e r r i t o r i a l d e f e n s e , I c l a s s i f i e d them as shown i n T a b l e I (p.25; a l s o see F i g . 5 ) . I d i s t i n g u i s h e d on- and o f f - d u t y b e h a v i o u r s by o b s e r v i n g t h e r e s i d e n t ' s r e a c t i o n t o a l l i n t r u d e r s p e r c e i v e d . When t h e r e were no i n t r u d e r s , i f t h e r e s i d e n t ' s b e h a v i o u r a l s t a t u s was i n d o u b t , I u s e d a b u l b f l y model or a s m a l l p e b b l e t o see whether t h e f l y would r e s p o n d . I a n a l y z e d t h e d a t a u s i n g t h e " s t r e a k " p r o g r a m ( s e e M a t e r i a l s and M e t h o d s ) . The r e s u l t i n g f r e q u e n c y d i s t r i b u t i o n of b e h a v i o u r s i s shown i n A p p e n d i x I I A 1 . The most f r e q u e n t b e h a v i o u r a l s e q u e n c e s were t h o s e e n d i n g i n "watch" o r " p a t r o l " . W i t h i n "watch" s e q u e n c e s , t h e most f r e q u e n t p a t t e r n s were " w a t c h - p a t r o l - w a t c h " and " w a t c h - c h a s e - w a t c h " . W i t h i n " p a t r o l " s e q u e n c e s , t h e most f r e q u e n t p a t t e r n s were " p a t r o l - w a t c h -p a t r o l " and " c h a s e - w a t c h - p a t r o l " ( A p p e n d i x I I A 2 , I I A 3 ) . The a n a l y s i s i n d i c a t e d t h a t t h e b a s i c b e h a v i o u r a l p a t t e r n i n 44 F i g u r e 5. B e h a v i o u r s o f t e r r i t o r i a l M. e q u e s t r i s m a l e s , (a) "watch": A male o n - d u t y , f a c i n g t h e open s p a c e , w a t c h i n g f o r i n t r u d e r s ; (b) "nbask": A male o n - d u t y , body a n g l e d t o w a r d t h e sun; ( c ) "ngroom": A male on-d u t y , g r o o m i n g ; (d) " r e s t " : A male o f f - d u t y , r e s t i n g under a l e a f away from h i s t e r r i t o r y . 45 46 47 t e r r i t o r i a l d e f e n s e i s an a l t e r n a t i o n between "watch" and " p a t r o l " , where "watch" i s p r e e m p t e d by "nbask" i f t h e a i r i s c o o l , and " p a t r o l " p r e e m p t e d by " c h a s e " when an i n t r u d e r i s p r e s e n t . V a r i a t i o n s i n T e r r i t o r i a l B e h a v i o u r P a t t e r n s The b a s i c t e r r i t o r i a l d e f e n s e p a t t e r n s ( w a t c h - p a t r o l -watch, w a t c h - c h a s e - w a t c h ) were most e v i d e n t i n uncrowded, w e l l -e s t a b l i s h e d t e r r i t o r i a l m a l e s . Such m a l e s were r a r e : of t h e 27 t e r r i t o r i a l m a les o b s e r v e d , o n l y t h r e e e s t a b l i s h e d t e r r i t o r i e s i n a r e a s where c o n s p e c i f i c m a l e s o r o t h e r i n t r u d e r s were r a r e . In s u c h p l a c e s , t h e " w a t c h - p a t r o l " r o u t i n e was i n t e r r u p t e d o n l y when t h e r e s i d e n t mated o r t e m p o r a r i l y l e f t t h e t e r r i t o r y . Most time was s p e n t w a t c h i n g , l e s s i n p a t r o l l i n g , and s t i l l l e s s i n c h a s i n g ( T a b l e I I ) . S p a t i a l d e f e n s e p a t t e r n s were as c o n s i s t e n t and r o u t i n e a s b e h a v i o u r a l p a t t e r n s : an uncrowded male r e p e a t e d l y p a t r o l l e d t h e same r o u t e and r e m a i n e d f a i t h f u l t o th e same watch s i t e ( s ) ( F i g . 6 ) . I n d i v i d u a l p a t t e r n s o f t e r r i t o r i a l b e h a v i o u r v a r i e d w i t h t e m p e r a t u r e and s u n l i g h t , l o c a l w e a t h e r , and c r o w d i n g ( i . e . , f r e q u e n c y of i n t r u s i o n s and t h e i d e n t i t i e s o f i n t r u d e r s ). One s t r i k i n g i n d i v i d u a l d i f f e r e n c e i n r e s p o n s e was a p p a r e n t l y due t o d i f f e r e n c e s i n l i f e s t a g e ( q . v . P . 5 4 ) . 48 F i g u r e 6. P a t r o l r o u t e s of M . . e q u e s t r i s m a l e s . (a) R o u t e s of an uncrowded male; (b) of a crowded male. H a t c h e d a r e a s i n d i c a t e p l a n t s . Note t h a t s p a t i a l p a t r o l p a t t e r n s between uncrowded and crowded m a l e s do n o t v a r y s i g n i f i c a n t l y . 49 50 T a b l e I I . Time a l l o c a t i o n by M. e q u e s t r i s m ale. B e h a v i o u r Time a l l o c a t e d (%) watch 73.6 nbask n f e e d ngroom p a t r o l 17.2 c h a s e 5.3 c h a s e c o n t a c t i n s p e c t 1.2 J_. S u n l i q h t and t e m p e r a t u r e The p r e s e n c e of f u l l s u n l i g h t seemed more c r i t i c a l f o r t e r r i t o r i a l a c t i v i t y t h a n t h e t e m p e r a t u r e l e v e l . F o r example, when a c l o u d p a s s i n g o v e r t h e sun c a u s e d a i r t e m p e r a t u r e s t o f a l l f r o m 24 t o 22°C, t e r r i t o r i a l m a l e s s t o p p e d f l y i n g as soon as t h e sun was o b s c u r e d , and r e m a i n e d i n a c t i v e ( o f f - d u t y ) u n t i l i t r e t u r n e d . ( D u r i n g s u c h i n a c t i v e p e r i o d s , m a l e s b a s k e d i n t h e s t i l l - a v a i l a b l e r a d i a n t h e a t , groomed, o r f e d . ) In c o n t r a s t , as l o n g as t h e sun was not c o v e r e d , males r e m a i n e d a c t i v e a t an a i r t e m p e r a t u r e of 22°C. When a i r t e m p e r a t u r e s i n sunny a r e a s f e l l below 20°C, m ales c u r t a i l e d or c e a s e d t e r r i t o r i a l d e f e n s e a c t i v i t i e s ( p a t r o l l i n g , i n s p e c t i n g , c h a s i n g ) and f e d or went t o b a s k i n g s i t e s on t h e s o i l . I f t h e t e m p e r a t u r e r e m a i n e d below 20°C f o r s e v e r a l min, males l e f t t h e i r t e r r i t o r i e s f o r t h e i r r e s t i n g s i t e s , o r s i m p l y b a s k e d on t h e s o i l i n t h e i r t e r r i t o r i e s . When 51 a i r t e m p e r a t u r e s h o v e r e d a r o u n d 20°C, m a l e s i n t e r s p e r s e d p a t r o l l i n g and c h a s i n g w i t h o n - d u t y b a s k i n g on t h e s o i l o r on v e g e t a t i o n w i t h i n 0.3 m o f g r o u n d . As a i r t e m p e r a t u r e s i n c r e a s e d , t h e d u r a t i o n and f r e q u e n c y of p a t r o l f l i g h t s and c h a s e s i n c r e a s e d ; a l t h o u g h i n s e c t s s t i l l b a s k e d o n - d u t y between f l i g h t s , b a s k i n g i n t e r l u d e s were s h o r t e r . B a s k i n g o c c u r r e d on v e g e t a t i o n 0.3-0.75 m above th e s o i l . ( A i r t e m p e r a t u r e s c o u l d be e s t i m a t e d by u s i n g b a s k i n g m a l e s as " t h e r m o m e t e r s " : i f m a l e s were b a s k i n g on t h e s o i l , t e m p e r a t u r e s were <20° C ; i f b a s k i n g m ales were w i t h i n 0.15 m of t h e s o i l , t e m p e r a t u r e s were 20-22°C; and i f t h e y were b a s k i n g a t 0.15-0.60 m above t h e s o i l , t e m p e r a t u r e s were > 2 2 ° C . ) A male c o u l d become t o o h o t ; . e . g . , when the a i r t e m p e r a t u r e on a c a l m day r e a c h e d 27°C, s o i l s u r f a c e t e m p e r a t u r e r e a c h e d 5 0 - 5 5 ° C , and s u n l i t l e a v e s a v e r a g e d 33°C. T e r r i t o r i a l m ales s h i f t e d t h e i r o u t l o o k p o s t s t o l e a v e s i n d a p p l e d or f u l l shade, where t h e l e a f t e m p e r a t u r e s were o n l y 23°C. At s u c h t i m e s , t h e i n s e c t s a v o i d e d p r e v i o u s l y - f r e q u e n t e d s i t e s on b e g o n i a l e a v e s , w h i c h were a s warm as 33°C i n t h e s h a d e . 2. A d d i t i o n a l weather e f f e c t s M a l e s d i d not f l y o r f e e d d u r i n g t h e e v e n i n g o r d u r i n g p e r i o d s of r a i n y w e a t h e r . T h e r e f o r e , i n t h e m o r n i n g u n t i l a p p r o x i m a t e l y 0930 ( d e p e n d i n g on t e m p e r a t u r e ) , o r when t h e weather i m p r o v e d a f t e r one o r more d a y s of bad w e a t h e r , m a l e s f e d t o r e p l e t i o n and b a s k e d b e f o r e becoming t e r r i t o r i a l . 52 _3. C r o w d i n g by c o n s p e c i f i e s The most i n t e r e s t i n g v a r i a t i o n s i n b e h a v i o u r p a t t e r n s o c c u r r e d when a r e s i d e n t male was crowded and t h e r e f o r e c h a l l e n g e d w i t h i n c r e a s e d f r e q u e n c y by one or more c o n s p e c i f i c s . When weather c o n d i t i o n s were c o n d u c i v e t o male f l i g h t a c t i v i t y , many k i n d s of b e e s , wasps, f l i e s and o t h e r i n s e c t s a l s o were more a c t i v e , so t h e d e f e n d i n g r e s i d e n t was c o n f r o n t e d by an i n c r e a s e d number of i n t r u d e r s , b o t h c o n s p e c i f i c and a l i e n . R e p e a t e d i n t r u s i o n s i n t e r r u p t e d f e e d i n g and g r o o m i n g b o u t s , t h u s p r e v e n t i n g a r e s i d e n t f r o m f e e d i n g t o r e p l e t i o n . Such i n t r u s i o n s a l s o p r e v e n t e d t h e r e s i d e n t from g o i n g t o o f f - d u t y s i t e s o u t s i d e t h e t e r r i t o r y t o r e s t u n d i s t u r b e d ; i f he l e f t h i s t e r r i t o r y d u r i n g s u c h p e r i o d s of i n c r e a s e d a c t i v i t y , t h e r e s i d e n t e f f e c t i v e l y f o r f e i t e d i t t o one o f t h e i n t r u d i n g c o n s p e c i f i c m a l e s , w h i c h t h e r e b y became t h e new r e s i d e n t . In e f f e c t , a r e s i d e n t i n a c r owded s i t u a t i o n was not o n l y c o n f i n e d t o h i s t e r r i t o r y , b ut was a l s o u n a b l e t o f e e d or groom w i t h o u t i n t e r r u p t i o n s . The r e s u l t o f s u c h c o n s t r a i n t s was i n c r e a s e d a g g r e s s i o n . S u ch h e i g h t e n e d a g g r e s s i o n was m a n i f e s t e d by c h a n g e s i n b e h a v i o u r p a t t e r n s : t h e male s t a y e d o n - d u t y , c h a s e d more k i n d s of i n t r u d e r s t h a n u s u a l ( e . g . , s h a d o w s ) , and s t r u c k more o f t h e i n t r u d e r s he p u r s u e d ( T a b l e I I I ) . A m a l e ' s r e a c t i o n t o i n t r u d e r s p r o v i d e d an a c c u r a t e i n d e x of h i s a g g r e s s i v e n e s s , and t h e r e f o r e of h i s "crowded s t a t e ". T e r r i t o r i a l m a l e s n o r m a l l y c o n t a c t t h r e e k i n d s of i n t r u d e r s : c o n s p e c i f i c f e m a l e s , c o n s p e c i f i c m a l e s ( w h i c h u s u a l l y h i t 53 T a b l e I I I . R e s p o n s e s of s i x M. e q u e s t r i s males t o i n t r u d e r s . E a c h row o f d a t a i l l u s t r a t e s t h e r e a c t i o n of one m a l e . S t a t e o f male R e a c t i o n t o i n t r u d e r s T o t a l c h a s e c h a s e - c o n t a c t c r o wded by c o n s p e c i f i c s 13 11 24 and a l i e n s 13 7 20 crowded by 26 0 26 a l i e n s o n l y 1 2 . 2 14 uncrowded 8 1 9 3 3 6 b a c k ) , and v a r i o u s k i n d s of bees ( w h i c h a r e u s u a l l y h i t one or s e v e r a l t i m e s u n t i l t h e y l e a v e t h e t e r r i t o r y ) . I n t r u d i n g . b e e s may be s t r u c k by crowded o r uncrowded m a l e s , a l t h o u g h t h e l a t t e r a r e more l i k e l y t o c h a s e w i t h o u t s t r i k i n g , whereas crowded, a g g r e s s i v e males u s u a l l y s t r i k e r e p e a t e d l y u n t i l t h e bee i s d r i v e n from t h e t e r r i t o r y . Uncrowded, l e s s a g g r e s s i v e m a l e s s c r e e n i n t r u d e r s v i s u a l l y b e f o r e c h a s i n g them and a p p a r e n t l y i g n o r e or m e r e l y i n s p e c t i n t r u d e r s t h a t have s i l h o u e t t e s u n l i k e b u l b f l i e s . Thus uncrowded m a l e s n o t i c e b ut i g n o r e shadows, s m a l l f l i e s , wasps, b u t t e r f l i e s and p e o p l e , whereas crowded males w i l l c h a s e and h i t e v e r y t h i n g but shadows and p e o p l e , w h i c h a r e i n s p e c t e d . The d i f f e r e n c e between t h e two l e v e l s of a g g r e s s i o n i s r e a d i l y a p p a r e n t t o an o b s e r v e r t r y i n g t o o b t a i n c l o s e u p p h o t o g r a p h s ! C r o w d i n g a l s o a f f e c t e d b e h a v i o u r a f t e r m a t i n g . Crowded 54 m a l e s resumed t h e i r s e n t i n e l p o s t s i m m e d i a t e l y a f t e r m a t i n g . Of s e v e n s u c h m a l e s o b s e r v e d , one watched and f e d ( n f e e d ) , t h r e e w atched and b a s k e d ( n b a s k ) , and two began t o p a t r o l . The s e v e n t h began an o f f - d u t y b e h a v i o u r ( fgroom) but w i t h i n 5 s c h a s e d a male c o n s p e c i f i c . However, uncrowded m a l e s r e m a i n e d o f f - d u t y f o r s e v e r a l min a f t e r m a t i n g . Of t h e t h r e e o b s e r v e d , two s a t f o r 3-5 min a f t e r m a t i n g . The t h i r d w atched and b a s k e d ( n b a s k ) , but had a l s o b a s k e d f o r most of t h e 5 min p r e c e d i n g m a t i n g . T h e r e f o r e , p r o v i d e d t h e y a r e not h a r a s s e d , m a l e s a p p a r e n t l y p r e f e r t o r e m a i n o f f - d u t y f o r s e v e r a l min a f t e r m a t i n g . S p a t i a l p a t t e r n s showed fewer c h a n g e s t h a n b e h a v i o u r a l p a t t e r n s as c r o w d i n g i n c r e a s e d : m a l e s r e t a i n e d t h e same p a t r o l r o u t e s and d i d not d e f e n d s m a l l e r a r e a s . I f a n y t h i n g , t e r r i t o r i e s grew t o i n c l u d e p r e v i o u s o f f - d u t y s i t e s as t h e r e s i d e n t began t o r e a c t t o h a r a s s m e n t a t or n e a r t h o s e s i t e s . An example i s shown i n F i g . 7 , where a m a l e ' s t e r r i t o r y e x panded t o i n c l u d e b o t h beds 2 and 3 a f t e r he was r e p e a t e d l y h a r a s s e d a t p r e v i o u s l y - n e u t r a l bed 3. 4. I n s e c t age and s t a g e A l l b u t one male o b s e r v e d d u r i n g 1980-81 e i t h e r had a l r e a d y e s t a b l i s h e d t e r r i t o r i e s b e f o r e t h e b e g i n n i n g o f t h e o b s e r v a t i o n s , o r e l s e were a t t e m p t i n g t o d r i v e out r e s i d e n t s d u r i n g t h e o b s e r v a t i o n p e r i o d . The e x c e p t i o n e x h i b i t e d b e h a v i o u r a l p a t t e r n s r a d i c a l l y d i f f e r e n t f r o m t h o s e o f t h e o t h e r s . A l t h o u g h o b s e r v a t i o n s on one i n d i v i d u a l do n o t u s u a l l y 55 F i g u r e 7. E x p a n s i o n of an M. e q u e s t r i s t e r r i t o r y i n r e s p o n s e t o c r o w d i n g by c o n s p e c i f i c s . S o l i d l i n e shows i n i t i a l Bed 2 t e r r i t o r y ; d a s h e d l i n e shows t e r r i t o r y e x p a n s i o n t o i n c l u d e Bed 3 i n r e s p o n s e t o h a r a s s m e n t a t o f f - d u t y s i t e s t h e r e . H a t c h e d a r e a s i n d i c a t e b a c k d r o p o f h i g h v e g e t a t i o n i n e a c h b e d . 56 57 p r o v i d e a. s u f f i c i e n t base f o r t e s t i n g h y p o t h e s e s , t h e b e h a v i o u r of t h i s p a r t i c u l a r i n d i v i d u a l was n o t e w o r t h y f o r t h e manner i n w h i c h i t c l a r i f i e d t h e s e q u e n c e o f c h a n g e s i n b e h a v i o u r d u r i n g an i m p o r t a n t t r a n s i t i o n p e r i o d i n a b u l b f l y ' s l i f e . The e x c e p t i o n a l male came from o u t s i d e t h e s t u d y a r e a . He was o b v i o u s l y newly-emerged: h i s wings were i n t a c t and s h i n y , h i s body p i l e dense and u n b r o k e n , and h i s c o l o u r p a t t e r n was s t i l l f r e s h and v i v i d ( F i g . 8 ) . He f l e w i n t o t h e s t u d y a r e a 3-5 m a b o v e . t h e lawn, much h i g h e r t h a n t e r r i t o r i a l m a l e s , w h i c h s e l d o m f l y a s h i g h as 2 m , and keep t h e i r t e r r i t o r i a l a c t i v i t y , e x c e p t d u r i n g c h a s e s , w i t h i n 1 m of t h e g r o u n d . The h e i g h t and d i r e c t i o n o f t h i s m a l e ' s a p p r o a c h p a t h , and h i s e n s u i n g b e h a v i o u r s t r o n g l y s u g g e s t t h a t , w h i l e on h i s o b l i g a t o r y d i s p e r s a l f l i g h t a f t e r emergence, t h i s f l y became t r a p p e d i n t h e s t u d y a r e a as midday z e n i t h p o l a r i z a t i o n waned ( W e l l i n g t o n , 1974a) and t h a t , w h i l e r e s t r i c t e d t o t h e s i t e , he g r a d u a l l y t e r m i n a t e d d i s p e r s a l b e h a v i o u r and i n i t i a t e d t e r r i t o r i a l b e h a v i o u r . The male e n t e r e d t h e s t u d y a r e a from t h e s o u t h e a s t t h r o u g h a gap between two c o r n e r t r e e s . H i s s e t t l i n g c o i n c i d e d w i t h t h e d i s a p p e a r a n c e o f o v e r h e a d p l a n e - p o l a r i z e d l i g h t a t 1213 on J u l y 17 ( A p p e n d i x I ) . [ T h a t h i s s e t t l i n g was r e l a t e d t o t h e t i m e when t h e p l a n e - p o l a r i z e d l i g h t d i s a p p e a r e d o v e r h e a d was s u p p o r t e d by t h e f a c t t h a t i n s e c t s f a m i l i a r w i t h t h e s t u d y s i t e , ( e . g . , a b a l d - f a c e d h o r n e t , marked and o b s e r v e d f o r 10 d a y s p r e v i o u s l y ) , a t t h a t moment s t o p p e d f l y i n g d i a g o n a l l y a c r o s s t h e open lawn and i n s t e a d began t o use l a n d m a r k s a l o n g 58 F i g u r e 8. The newly-emerged M. e q u e s t r i s male d e s c r i b e d on p.55. Note t h e dense u n b r o k e n p i l e , s h i n y i n t a c t w i n g s , and v i v i d c o l o u r p a t t e r n . 60 t h e e dges of t h e lawn, ( e . g . , gaps i n t h e s h r u b b e r y ) , f o r t h e i r p o i n t - t o - p o i n t t r a v e l s . ] I i n i t i a l l y f a i l e d t o r e c o g n i z e t h e male a s a b u l b f l y b e c a u s e he b e h a v e d f o r t h e f i r s t few m i n u t e s more l i k e a bumblebee or a d r o n e f l y , h o v e r i n g r e p e a t e d l y above a p r o m i n e n t p a t c h of d a i s i e s 1.5 m h i g h . Between s a c c a d e s , he f l e w r e p e a t e d l y t o w a r d e a c h o f t h e f o u r c o r n e r s o f t h e s t u d y a r e a , f a v o u r i n g t h e s o u t h e a s t c o r n e r gap t h r o u g h w h i c h he had a r r i v e d . F o r t h e n e x t 10 min, he e x e c u t e d a number of t h e l o n g , slow upward s p i r a l s t h a t a r e so c h a r a c t e r i s t i c of i n s e c t s a b o u t t o b e g i n d i r e c t e d f l i g h t [ e . g . , t h e " t o w e r i n g " of d i s p e r s i n g c o c c i n e l l i d s (Hagen, 1962), t h e s p r u c e budworm (Greenbank e t a l . , . 1980) and many o t h e r k i n d s of m i g r a t i n g i n s e c t s (Southwood, 1962; W e l l i n g t o n , 1 9 6 4 ) ] . E a c h began a t h i s h o v e r i n g s i t e , e x t e n d e d as h i g h as 7 m above g r o u n d and t e r m i n a t e d w i t h a l o n g , slow, downward s p i r a l , back t o t h e h o v e r i n g s i t e . The upward s p i r a l s were i n t e r s p e r s e d w i t h r a p i d " e s c a p e f l i g h t s " , a t h e i g h t s o f 5-7 m, t o any o f t h e s t u d y s i t e b o u n d a r i e s o r c o r n e r s . T h i s c o m b i n a t i o n of o r i e n t a t i o n s p i r a l s and a p p a r e n t l y p u r p o s e f u l f l i g h t s t o w a r d s p o t e n t i a l e x i t s from an open s p a c e bounded by w e l l - m a r k e d edges i s c h a r a c t e r i s t i c of i n s e c t s h a l t e d d u r i n g t h e i r d i s p e r a l by i n t e r r u p t i o n s i n t h e i r n a v i g a t i o n a l a i d , p o l a r i z e d l i g h t ( W e l l i n g t o n , 1974a). A l t h o u g h t h i s male d i d not a l i g h t , f e e d , o r groom d u r i n g t h o s e f i r s t 10 min, t o w a r d t h e end of t h a t p e r i o d , he began t o behave t e r r i t o r i a l l y by c h a s i n g a l l a i r b o r n e i n s e c t s he e n c o u n t e r e d d u r i n g h i s f l i g h t s . The o t h e r i n s e c t s f l y i n g d u r i n g t h a t t i m e were m o s t l y l a n d m a r k i n g bumblebees ( W e l l i n g t o n , 61 1974a), a l l c o n s i d e r a b l y l a r g e r t h a n t h e b u l b f l y . He c h a s e d e a c h one v i g o u r o u s l y , making, r e p e a t e d a u d i b l e and v i s i b l e c o n t a c t , u n t i l t h e v i c t i m r e a c h e d t h e edge of t h e s t u d y a r e a . The bees he p u r s u e d o f t e n a s c e n d e d as h i g h a s 7-10 m, but f a i l e d t o shake him o f f , even a t t h o s e h e i g h t s , u n t i l t h e y r e a c h e d a b o u n d a r y . T h i s b u l b f l y ' s f i r s t t e r r i t o r i a l manoeuvers t h u s t o o k p l a c e a t g r e a t e r h e i g h t s t h a n c o m p a r a b l e e n c o u n t e r s by e s t a b l i s h e d t e r r i t o r i a l m a l e s , w h i c h were c o n f i n e d t o w i t h i n 2 m of t h e s u r f a c e . In f a c t , t h i s f l y was a i r b o r n e f o r v i r t u a l l y a l l of t h e f i r s t 22 min a f t e r h i s a r r i v a l a t t h e s i t e : when not h o v e r i n g , he was c h a s i n g b e e s o r making o r i e n t a t i o n s p i r a l s . He d i d not b e g i n t o f e e d u n t i l min 23, and even t h e n f e e d i n g b o u t s were b r i e f (1-2 s ) . L o n g e r f e e d i n g b o u t s - 25, 15, and 40 s r e s p e c t i v e l y - f o l l o w e d , and c o i n c i d e d w i t h t h e o n s e t of p a t r o l f l i g h t s , c h a s e s a t l e s s e r h e i g h t s , l o n g e r , more f r e q u e n t l a n d i n g s , and fewer s p i r a l s and f l i g h t s t o w a r d c o r n e r s . [However, s p i r a l s began a t min 37, w h i l e c i r r u s c l o u d s p a s s e d t h r o u g h t h e z e n i t h ( W e l l i n g t o n , 1953).] D e s p i t e t h e o n s e t of s e t t l i n g b e h a v i o u r , t h e male o n l y r e s p o n d e d t o i n t r u d e r s w h i l e he was h o v e r i n g o r f l y i n g , and t h e n o n l y c h a s e d a i r b o r n e i n s e c t s . D u r i n g t h e f i r s t 38 min f o l l o w i n g h i s a r r i v a l , when he was f e e d i n g o r g r o o m i n g on a f l o w e r , he i g n o r e d a l l i n t r u d e r s f l y i n g or c r a w l i n g w i t h i n h i s range of v i s i o n ; e.g., bumble b e e s , wasps, and one u n i d e n t i f i e d s m a l l i n s e c t w h i c h c r a w l e d r i g h t o v e r him. F u r t h e r m o r e , w h i l e h o v e r i n g , he i g n o r e d a l l bees f e e d i n g on t h e f l o w e r s b e n e a t h 62 him, a l t h o u g h he was c l o s e enough t o p e r c e i v e t h e i r movements. At min 39, however, he e x h i b i t e d more c o n v e n t i o n a l t e r r i t o r i a l b e h a v i o u r by r i s i n g from a d a i s y f l o w e r t o c h a s e a f l y i n g i n t r u d e r . T h e r e a f t e r , he behaved i n c r e a s i n g l y l i k e an e s t a b l i s h e d male; f e e d i n g f o r m i n u t e s a t a t i m e , o c c a s i o n a l l y s e e k i n g r e s t s p o t s under l e a v e s ( F i g . 5 d ) , and r e s t r i c t i n g t h e h e i g h t a t w h i c h he r e s p o n d e d t o and c h a s e d i n t r u d e r s . He became v e r y e a s y t o a p p r o a c h and p h o t o g r a p h , and r e m a i n e d on what had become h i s t e r r i t o r y when t h e o v e r h e a d p o l a r i z a t i o n r e t u r n e d l a t e r i n t h e a f t e r n o o n . R e c o g n i t i o n of I n t r u d e r s M a l e s u s e d v i s u a l and b e h a v i o u r a l c u e s t o i d e n t i f y i n t r u d e r s . A male v i s u a l l y s c r e e n e d i n t r u d e r s as t h e y e n t e r e d h i s t e r r i t o r y , and u s u a l l y i g n o r e d t h o s e w h i c h d i d not l o o k (and p e r h a p s d i d not sound) l i k e c o n s p e c i f i c s . Thus b u t t e r f l i e s , shadows, b i r d s and wasps were u s u a l l y i g n o r e d . I n t r u d e r s l i k e bees and f l i e s were i n s p e c t e d , c h a s e d o r h i t . C o n s p e c i f i c m ales were a l w a y s c h a s e d and, i f p o s s i b l e , h i t ; male-male c o n f r o n t a t i o n s i n v o l v e d l o n g s e q u e n c e s of c h a s i n g and f r e q u e n t , a u d i b l e c o n t a c t u n t i l one ( u s u a l l y t h e i n t r u d e r ) was d r i v e n o f f . C o n s p e c i f i c f e m a l e s were c o n t a c t e d but n e v e r h i t : c o n t a c t i n v o l v e d c l a s p i n g and was a l w a y s a p r e l u d e t o m a t i n g . S e v e r a l males a t t e m p t e d t o mate w i t h o t h e r m a l e s , but I n e v e r saw a male make t h e r e v e r s e " m i s t a k e " , i . e . , t r y t o d r i v e a f e m a l e away. Such one-way m i s t a k e s i n d i c a t e t h a t a t e r r i t o r i a l male i d e n t i f i e s f e m a l e s by t h e i r b e h a v i o u r as w e l l 63 as by t h e i r a p p e a r a n c e (and ..perhaps by t h e sound t h e y make). A l l m a l e - f e m a l e c o n t a c t s - o b s e r v e d i n v o l v e d a c h a s e ( i f t h e f e m a l e was a i r b o r n e ) and c o n t a c t , a f t e r w h i c h t h e f e m a l e l a n d e d and m a t i n g o c c u r r e d . I f she was b a s k i n g o r f e e d i n g when c o n t a c t o c c u r r e d , she r e m a i n e d on t h a t s p o t d u r i n g m a t i n g . By c o n t r a s t , c o n s p e c i f i c m a l e s f o u g h t back when c o n t a c t e d , w h i l e b e e s and o t h e r i n t r u d e r s . f l e d . In a l l " m i s t a k e s " o b s e r v e d , t h e t e r r i t o r i a l male began by r e p e a t e d l y h i t t i n g a f e e d i n g i n t r u d e r - when t h e i n t r u d e r d i d n o t r e s p o n d , t h e male a t t e m p t e d t o c o u p l e w i t h i t . T h i s c a u s e d t h e i n t r u d e r t o shake o f f t h e male and f l y away. 64 THE LESSER BULB FLY, EUMERUS TUBERCULATUS Importance-" L e s s e r b u l b f l y " i s t h e common name g i v e n t o two v e r y s i m i l a r s p e c i e s : Eumerus t u b e r c u l a t u s , u s u a l l y f o u n d i n n a r c i s s u s , and E. s t r i q a t u s ( F a l l . ) , u s u a l l y f o u n d i n i r i s , h y a c i n t h , p a r s n i p and p o t a t o , and o c c a s i o n a l l y i n n a r c i s s u s . F o r p r a c t i c a l p u r p o s e s , t h e two a r e o f t e n c o n s i d e r e d one s p e c i e s , s i n c e t h e m o r p h o l o g y of e a c h l i f e s t a g e i s v e r y s i m i l a r i n b o t h and b e c a u s e , i n n a r c i s s u s , i n d i v i d u a l s of b o t h s p e c i e s have t h e same h a b i t s (Hodson, 1927; W o o d v i l l e , 1970). However, t h e o n l y i n s e c t s d i s c u s s e d h e r e were p o s i t i v e l y i d e n t i f i e d a s E. t u b e r c u l a t u s . E. t u b e r c u l a t u s i s n o t so s e r i o u s a p e s t a s M. e q u e s t r i s , but i t i s n o n e t h e l e s s a p r i m a r y p e s t of n a r c i s s u s . Newly-emerged l a r v a e a r e c a p a b l e of e n t e r i n g h e a l t h y b u l b s , a l t h o u g h l a r v a e of s u b s e q u e n t i n s t a r s can o n l y p e n e t r a t e unsound b u l b s [ e . g . , b u l b s a l r e a d y a t t a c k e d by t h e stem eelworm (Hodson, 1 9 2 7 ) ] . P r e s e n c e o f l a r v a e i n b u l b s i s t h e r e f o r e u s u a l l y a symptom of o t h e r d i s e a s e o r p e s t p r o b l e m s ( W o o d v i l l e , 1970). 65 B i o l o g y and L i f e H i s t o r y A d u l t s a r e a p p r o x i m a t e l y 6 mm l o n g . They c l o s e l y r e s e m b l e h a l i c t i d bees ( F i g . 9 ) . L i k e h a l i c t i d s , E. t u b e r c u l a t u s a d u l t s a r e b l a c k w i t h a m e t a l l i c - g r e e n t o - b r o n z e t i n t , l a c k p u b e s c e n c e , a n d have t h r e e p a i r s o f w h i t e c r e s e n t - s h a p e d marks on t h e abdomen (Woodville., 1970). M a l e s a r e u s u a l l y s m a l l e r t h a n f e m a l e s , and have e y e s t h a t meet i n t h e m i d d l e of t h e f a c e ( F i g . 1 0 ) . W o o d v i l l e (1970) s t a t e s t h a t a d u l t f l i e s f i r s t a p p e a r i n t h e f i e l d l a t e i n A p r i l , and t h a t i n d i v i d u a l s of s u c c e s s i v e g e n e r a t i o n s may be a c t i v e u n t i l e a r l y O c t o b e r . M a l e s emerge a p p r o x i m a t e l y t h r e e d a y s e a r l i e r t h a n f e m a l e s . In c a p t i v i t y , t h e f o r m e r l i v e f o r an a v e r a g e o f 13 d a y s , t h e l a t t e r f o r 15. The f l i e s u s u a l l y c o m p l e t e two g e n e r a t i o n s p e r y e a r , l e s s f r e q u e n t l y one, and o c c a s i o n a l l y a p a r t i a l t h i r d . L a r v a e o f a p a r t i a l t h i r d g e n e r a t i o n o v e r w i n t e r i n b u l b s and p u p a t e d u r i n g t h e f o l l o w i n g s p r i n g ; pupae n e v e r o v e r w i n t e r (Hodson, 1927). E. t u b e r c u l a t u s m a l e s a r e t e r r i t o r i a l ( p e r s . obs.) and, l i k e M. e q u e s t r i s m a l e s , a t t e m p t t o mate w i t h a l l c o n s p e c i f i c f e m a l e s w h i c h e n t e r t h e i r t e r r i t o r i e s ( F i g . 1 l ) . However, t h e r e a r e t h r e e n o t a b l e d i f f e r e n c e s among m a l e - f e m a l e i n t e r a c t i o n s i n t h e two s p e c i e s . A l t h o u g h m a l e s of e a c h s p e c i e s i n i t i a t e m a t i n g by c l a s p i n g a f l y i n g o r s i t t i n g f e m a l e , E. t u b e r c u l a t u s m a l e s do not make a u d i b l e , f o r c e f u l c o n t a c t . In c o n t r a s t , E. t u b e r c u l a t u s f e m a l e s n e v e r a t t e m p t t o shake o f f a male as do M. e q u e s t r i s f e m a l e s ( p e r s . o b s . ) . Hodson (1927) r e p o r t e d t h a t , a l t h o u g h m a l e s mate r e p e a t e d l y , "a f e m a l e once mated a v o i d s 66 F i g u r e 9. Eumerus t u b e r c u l a t u s and h a l i c t i d . (a) An E. t u b e r c u l a t u s male. (b) An u n i d e n t i f i e d h a l i c t i d bee f o r c o m p a r i s i o n . 68 F i g u r e 10. E. t u b e r c u l a t u s m a l e . Note t h a t t h e e y e s meet i n t h e m i d d l e of t h e f a c e . 69 70 f u r t h e r a d v a n c e s " , but d i d not say how f u r t h e r c o n t a c t was p r e v e n t e d . The t h i r d d i f f e r e n c e between t h e two s p e c i e s i s t h a t , a l t h o u g h t h e m a t i n g p r o c e s s t a k e s a p p r o x i m a t e l y t h e same l e n g t h of t i m e i n b o t h , no s e p a r a t e s t a g e s a r e d i s c e r n i b l e i n E. t u b e r c u l a t u s p a i r s , and n e i t h e r male nor f e m a l e e v e r e m i t t e d t h e h i g h - p i t c h e d n o i s e common t o M. e q u e s t r i s ( p e r s . o b s . ) . W i t h i n .2-3 days a f t e r f e r t i l i z a t i o n , a f e m a l e b e g i n s t o o v i p o s i t (Hodson, 1927). The e g g s , w h i c h a r e s h i n y , w h i t e , o v a l - s h a p e d and a p p r o x i m a t e l y 8 mm l o n g , a r e d e p o s i t e d i n c l u s t e r s of 5-40 a t or n e a r s o i l - l e v e l f o l i a g e . . L a r v a e h a t c h w i t h i n 3 d a y s , move t o t h e n e a r e s t b u l b and e n t e r i t t h r o u g h t h e neck r e g i o n ( u n l i k e M. e q u e s t r i s l a r v a e , w h i c h e n t e r t h r o u g h t h e b a s a l p l a t e ) . L a r v a e make no a t t e m p t t o burrow t h r o u g h t h e s o i l (Hodson, 1927). They t r a v e l down f o l i a g e t o t h e neck o f t h e b u l b , o r move a c r o s s t h e s o i l s u r f a c e u n t i l t h e y r e a c h t h e n e a r e s t clump of b u l b f o l i a g e , and t h e n t r a v e l down i t . F e e d i n g l a r v a e r a p i d l y r e d u c e t h e b u l b t i s s u e t o a p u l p y , r o t t i n g mass ( W o o d v i l l e , 1970). M a t u r e l a r v a e a r e s i m i l a r i n s i z e t o , and may be c o n f u s e d w i t h , s e c o n d - i n s t a r l a r v a e of M. e q u e s t r i s . The two a r e d i s t i n g u i s h e d by d i f f e r e n c e s i n t h e p o s t e r i o r r e s p i r a t o r y p r o c e s s : i n M. e q u e s t r i s , i t i s s h o r t , d a r k and s t u b b y , whereas i n E. t u b e r c u l a t u s , t h e p r o c e s s i s l o n g , s l e n d e r and b r i c k - r e d ( D o u c e t t e e t a l . , 1942). In a d d i t i o n , E . t u b e r c u l a t u s l a r v a e a r e f o u n d i n g r o u p s a t t h e neck of t h e b u l b amid a p u l p y , homogeneous mass of t i s s u e , whereas M. e q u e s t r i s l a r v a e a r e f o u n d s i n g l y i n a d i s t i n c t t u n n e l o r burrow w h i c h opens a t o r 71 F i g u r e 11. M a t i n g E . t u b e r c u l a t u s p a i r . 72 73 n e a r t h e b u l b ' s b a s a l p l a t e (op. c i t . ) . E. t u b e r c u l a t u s l a r v a e p u p a t e i n t o u g h , p e a r - s h a p e d , g r e y -brown p u p a r i a , , 6 mm l o n g , a t o r near t h e s o i l s u r f a c e . F i r s t -g e n e r a t i o n l a r v a e p u p a t e i n e a r l y J u l y , whereas t h o s e of t h e s e c o n d g e n e r a t i o n p u p a t e i n e a r l y f a l l o r o v e r w i n t e r i n b u l b s and p u p a t e d u r i n g t h e f o l l o w i n g J u l y (op. c i t . ) . R e s u l t s C h a r a c t e r i s t i c s o f a T e r r i t o r y T e r r i t o r i a l m ales were p r e s e n t i n t h e s t u d y a r e a from t h e f i r s t day of o b s e r v a t i o n s (May 7, 1980) u n t i l t h e l a s t ( A u gust 25, 1980). Emergence p r o b a b l y began i n l a t e A p r i l , a s s u g g e s t e d by W o o d v i l l e ( 1 9 7 0 ) . P o p u l a t i o n d e n s i t y p e a k e d t w i c e : f i r s t i n l a t e May and a g a i n between l a t e J u l y and e a r l y A u g u s t . B o t h peaks c o i n c i d e d w i t h p e r i o d s of warm, sunny w e a t h e r , and e a c h was p r o b a b l y i n d i c a t i v e of a s e p a r a t e g e n e r a t i o n . M a l e s d e f e n d e d a p p r o x i m a t e l y r e c t a n g u l a r t e r r i t o r i e s , w h i c h r a n g e d i n s i z e f r o m 0.9 m 2 t o 8.4 m 2, a v e r a g i n g 4 m 2 ( F i g . 1 2 ) . A r e s i d e n t d e f e n d e d t h e same t e r r i t o r y f o r up t o seve n d a y s , and r e t u r n e d t o d e f e n d i t a f t e r p e r i o d s of i n a c t i v i t y due t o bad w e a t h e r . L i k e M. e q u e s t r i s , E. t u b e r c u l a t u s m a l e s were u s u a l l y f o u n d i n sunny p a t c h e s of f l o w e r beds 1 and 2 ( F i g . 4 ) . However, u n l i k e t h e f o r m e r , w h i c h d e f e n d e d up t o t h r e e t e r r i t o r i e s w i t h i n t h e home r a n g e , E. t u b e r c u l a t u s males d e f e n d e d o n l y one t e r r i t o r y . A l t h o u g h t e r r i t o r i a l b o u n d a r i e s were not c o n t i g u o u s w i t h t h o s e of t h e 74 home range ( w h i c h m i g h t be as l a r g e as 11.2 m 2 ) , most of a m a l e ' s t i m e was s p e n t on h i s t e r r i t o r y . A l t h o u g h t h e s i z e of a.male's t e r r i t o r y v a r i e d l i t t l e , t e r r i t o r i a l b o u n d a r i e s o f t e n s h i f t e d as t h e r e s i d e n t moved. Sometimes movements and c o r r e s p o n d i n g b o u n d a r y s h i f t s were o b v i o u s l y a r e s u l t o f t h e r e s i d e n t f o l l o w i n g moving a r e a s of s u n l i g h t . At o t h e r t i m e s , no r e a s o n was a p p a r e n t ; t h e r e s i d e n t j u s t " took h i s t e r r i t o r y w i t h him" t o a new a r e a . Such " f l o a t i n g t e r r i t o r i e s " ( B i g g s , 1972) were o c c a s i o n a l l y m a i n t a i n e d by M. e q u e s t r i s m a l e s , but were much more common among E. t u b e r c u l a t u s m a l e s . M a l e s r e q u i r e d t h e same t e r r i t o r i a l f e a t u r e s as M. e q u e s t r i s m a l e s , t h o u g h on a s m a l l e r s c a l e . In f a c t , e a r l y i n t h e s e a s o n , t h e c e n t e r of the. p r e f e r r e d M. e q u e s t r i s t e r r i t o r y was a l s o t h e p r e f e r r e d E. t u b e r c u l a t u s t e r r i t o r y . ( D e s p i t e t h i s , t e r r i t o r i a l c o n f l i c t s were r a r e ; t e r r i t o r i a l i n d i v i d u a l s of e a c h s p e c i e s were u s u a l l y s e p a r a t e d by t i m e . The o n l y o b s e r v e d c o n f l i c t was s h o r t and ended when t h e s m a l l e r male r e t r e a t e d from t h e t e r r i t o r y . ) E. t u b e r c u l a t u s t e r r i t o r i e s i n c l u d e d a b a c k d r o p of v e g e t a t i o n , s e v e r a l f o o d p l a n t s , and open s p a c e n e a r a N a r c i s s u s p l a n t . T e r r i t o r i a l a c t i v i t i e s were a l w a y s r e s t r i c t e d t o 0.20-0.25 m above t h e g r o u n d . T e r r i t o r i a l B e h a v i o u r s M a l e s e x h i b i t e d a l m o s t a l l on- and o f f - d u t y b e h a v i o u r s d e s c r i b e d f o r M. e q u e s t r i s ( T a b l e I , F i g . 1 3 ) . The b e h a v i o u r n o t a b l y r a r e among E. t u b e r c u l a t u s m a l e s was " c h a s e - c o n t a c t " ; 75 F i g u r e 12. An E. t u b e r c u l a t u s t e r r i t o r y , showing p a t r o l and c h a s e r o u t e s d u r i n g a 5 min p e r i o d . H a t c h e d a r e a s i n d i c a t e p l a n t s . 76 77 i t was o n l y o b s e r v e d as t h e p r e l u d e t o m a t i n g , so t h a t " c o n t a c t " was a c t u a l l y " c l a s p " . No male e v e r s t r u c k a n o t h e r male nor any a l i e n i n t r u d e r . E q u a l l y r a r e was t h e b e h a v i o u r "go away". M a l e s s w i t c h e d from o n - d u t y t o o f f - d u t y by t u r n i n g t o f a c e t h e v e g e t a t i v e b a c k d r o p , and t h e r e f o r e s e l d o m l e f t t h e t e r r i t o r y t o r e s t , u n l i k e t h e o t h e r s y r p h i d s d i s c u s s e d h e r e . The b a s i c t e r r i t o r i a l d e f e n s e p a t t e r n was a c o m b i n a t i o n of " w a t c h - p a t r o l " and " w a t c h - c h a s e " , and was c l e a r l y e v i d e n t i n a l l m a les ( A p p e n d i x 11B1 - 3 ) . " I n s p e c t " was more, f r e q u e n t i n E. t u b e r c u l a t u s m a l e s t h a n i n M. e q u e s t r i s m a l e s : whereas t h e l a t t e r c h a s e d and h i t most i n t r u d e r s , t h e f o r m e r m i g h t r i s e t o i n s p e c t an i n t r u d e r , t h e n s e t t l e a g a i n w i t h o u t c h a s i n g ( T a b l e I V ) . T a b l e IV. R e s p o n s e s of E. t u b e r c u l a t u s m ales t o i n t r u d e r s . Male no. I n t r u d e r s C h ased I n s p e c t e d No r e s p o n s e T o t a l 1 8 1 1 10 2 20 8 1 31 3 1 1 0 2 4 6 0 1 7 5 6 2 0 8 6 9 0 0 9 78 F i g u r e 13. B e h a v i o u r s of t e r r i t o r i a l E. t u b e r c u l a t u s m a l e s , (a) "watch" ( o n - d u t y ) ; (b) "nbask": o n - d u t y basking., w i t h body f l a t t e n e d t o s u b s t r a t e ; ( c ) " f f e e d " : o f f - d u t y f e e d i n g . 79 80 81 V a r i a t i o n s i n T e r r i t o r i a l B e h a v i o u r P a t t e r n s M a l e s showed l i t t l e b e h a v i o u r a l v a r i a b i l i t y , and c o r r e s p o n d i n g l y l i t t l e v a r i a t i o n i n a g g r e s s i v e n e s s . L i k e t h e l a r g e r b u l b f l y , E. t u b e r c u l a t u s m a l e s were not t e r r i t o r i a l u n l e s s f u l l s u n l i g h t p r e v a i l e d and t h e a i r t e m p e r a t u r e was > 1 7 ° C . E. t u b e r c u l a t u s m a l e s d i d not f l y or f e e d d u r i n g t h e e v e n i n g o r d u r i n g p e r i o d s of r a i n y w e a t h e r . T h e r e f o r e , i n t h e m o r n i n g , o r f o l l o w i n g one o r more d a y s of r a i n , t h e y became, t e r r i t o r i a l o n l y a f t e r b a s k i n g and f e e d i n g t o r e p l e t i o n . C r o w d i n g , a l a r g e d e t e r m i n a n t of M. e q u e s t r i s b e h a v i o u r a l v a r i a t i o n , d i d not a c c o u n t f o r much v a r i a b i l i t y i n t h e b e h a v i o u r a l s t a t e o r i n t h e a g g r e s s i v e i n t e n s i t y o f E. t u b e r c u l a t u s . T h e r e a r e two o b v i o u s r e a s o n s f o r t h i s . One i s t h a t E. t u b e r c u l a t u s m a l e s r e m a i n e d on t h e i r t e r r i t o r i e s d u r i n g o f f - d u t y p e r i o d s , so t h a t r e p e a t e d i n t r u s i o n s c o u l d not d e p r i v e m a l e s o f o f f - d u t y b r e a k s . The s e c o n d i s t h a t E. t u b e r c u l a t u s m a l e s were n e v e r as crowded as t h e i r l a r g e r c o u n t e r p a r t s . Whereas M. e q u e s t r i s m a l e s commonly competed f o r a t e r r i t o r y w i t h two o r t h r e e c o n s p e c i f i c s , E. t u b e r c u l a t u s m a l e s were n e v e r e x p o s e d t o more t h a n one o t h e r male, and t h e n o n l y f o r s h o r t p e r i o d s . E. t u b e r c u l a t u s m a l e s m a i n t a i n e d s m a l l e r t e r r i t o r i e s (4 m 2) t h a n M. e q u e s t r i s m a l e s , w h i c h d e f e n d e d t e r r i t o r i e s a v e r a g i n g 17 m 2. Thus t h e s t u d y s i t e c o n t a i n e d 7-10 p o t e n t i a l E. t u b e r c u l a t u s t e r r i t o r i e s t h a t c o u l d accomodate 7-10 w e l l - s p a c e d m a l e s , but o n l y 2-3 M. e q u e s t r i s t e r r i t o r i e s w h i c h c o u l d accomodate no more t h a n t h r e e w e l l - s p a c e d m a l e s . An 82 E. t u b e r c u l a t u s male t h a t e n c o u n t e r e d a n . o c c u p i e d t e r r i t o r y was u s u a l l y a b l e t o move t o a n e i g h b o u r i n g t e r r i t o r y . T e r r i t o r i a l c o n f l i c t s between two su c h m a l e s i n v o l v e d o n l y o c c a s i o n a l b o u n d a r y s k i r m i s h e s , n ot t h e c o n s t a n t b a t t l e s c h a r a c t e r i s t i c o f two M. e q u e s t r i s males a t t e m p t i n g t o oc c u p y t h e same t e r r i t o r y . A l t h o u g h t h e y were n e v e r v e r y crowded, E. t u b e r c u l a t u s m a l e s d i d e x p e r i e n c e f l u c t u a t i o n s i n i n t r u d e r d e n s i t y w h i c h prompted c h a n g e s from a r e s i d e n t ' s " w a t c h - p a t r o l " p a t t e r n t o " w a t c h - c h a s e " b u t , w i t h one e x c e p t i o n , t h e i r r e l a t i v e l y low l e v e l of a g g r e s s i v e n e s s d i d n o t i n c r e a s e . The e x c e p t i o n a l male was engaged i n an uncommon c o n f l i c t w i t h a n o t h e r o v e r p o s s e s s i o n o f an e n t i r e t e r r i t o r y . He became i n c r e a s i n g l y a g g r e s s i v e a s t h e c o n f l i c t p r o g r e s s e d and r e p e a t e d l y c h a s e d a much l a r g e r f o r a g i n g l e a f c u t t e r b e e. However, a l l o t h e r t e r r i t o r i a l i n d i v i d u a l s were o n l y m o d e r a t e l y a g g r e s s i v e t h r o u g h o u t t h e c o u r s e of t h e s t u d y . I p r e s e n t e d t e r r i t o r i a l E . t u b e r c u l a t u s m a l e s w i t h a t h r e a d model i n an a t t e m p t t o e l i c i t c h a n g e s i n t h e i r b e h a v i o u r p a t t e r n s w h i c h might i n c r e a s e a g g r e s s i v e n e s s . T h e s e a t t e m p t s were u n s u c c e s s f u l b e c a u s e m a l e s l e a r n e d , a f t e r i n s p e c t i n g t h e model once o r t w i c e , t h a t i t was not a c o n s p e c i f i c and r e t r e a t e d from i t , o f t e n s h i f t i n g t h e i r t e r r i t o r i a l b o u n d a r i e s i n t h e p r o c e s s . Bad weather i n t e r f e r e d w i t h a d d i t i o n a l c r o w d i n g e x p e r i m e n t s p l a n n e d f o r 1981. 83 Recogn i t i o n of I n t r u d e r s M a l e s were a b l e t o see moving i n t r u d e r s a t d i s t a n c e s r a n g i n g f r o m 0.3 m ( a g a i n s t a v e g e t a t i v e b a c k d r o p ) t o 1 m ( a g a i n s t an u n b r o k e n b a c k d r o p s u c h as s k y ) . M a l e s i n s p e c t e d most i n t r u d e r s : c o n s p e c i f i c s , t i n y f l i e s , l a r g e b u l b f l i e s , v a r i o u s k i n d s of b e e s , and moving shadows and f e a t h e r s . L a r g e i n t r u d e r s ( e . g . , b e es) were a p p a r e n t l y r e c o g n i z e d f r o m a d i s t a n c e ; a l t h o u g h t h e y were i n s p e c t e d o r c h a s e d , t h e y were no t s u b j e c t e d t o m a t i n g a t t e m p t s . M a l e s a l s o c o u l d d i s t i n g u i s h t i n y f l i e s f r o m c o n s p e c i f i c s , s i n c e no male a t t e m p t e d t o mate w i t h a n y t h i n g but a c o n s p e c i f i c . However, m a l e s a p p a r e n t l y r e l i e d on b e h a v i o u r a l c u e s t o d i s t i n g u i s h c o n s p e c i f i c m a l e s from f e m a l e s . An i n t r u d i n g male showed a d e f i n i t e b e h a v i o u r a l r e s p o n s e t o an i n s p e c t i n g r e s i d e n t : he t u r n e d t o f a c e t h e r e s i d e n t and t h e two engaged i n p r o l o n g e d h e a d - t o - h e a d s p i r a l s . R e p e a t e d c o n t a c t , a c h a r a c t e r i s t i c o f M. e q u e s t r i s c o n f r o n t a t i o n s , n e v e r o c c u r r e d . S i n c e c o n s p e c i f i c f e m a l e s d i d n o t show any d i s c e r n a b l e b e h a v i o u r a l r e s p o n s e t o an i n s p e c t i n g male, t h e y may have been i d e n t i f i e d by a c o m b i n a t i o n o f c l o s e - u p pheromone and - o r sound i n a d d i t i o n t o t h e i r l a c k of b e h a v i o u r a l r e s p o n s e . A male n e v e r a t t e m p t e d t o c h a s e a f e m a l e away. A t t e m p t e d male-male m a t i n g s were r a r e , but o c c u r r e d when t h e i n t r u d i n g male d i d not r e a c t t o t h e r e s i d e n t ' s i n s p e c t i o n . 84 THE DRONE FLY, ERISTALIS TENAX I m p o r t a n c e , B i o l o g y and L i f e H i s t o r y E r i s t a l i s t e n a x i s n o t an a g r i c u l t u r a l p e s t , but i s w e l l -known as a B a t e s i a n mimic o f t h e honeybee A p i s m e l l i f e r a (Brower and Brower, 1965; H o l l o w a y , 1976; H e a l , 1979 and F i g . 1 4 ) . L i k e M. e q u e s t r i s , E. t e n a x has been t h e s u b j e c t of. g e n e t i c s t u d i e s ( H e a l , 1979), and has a l s o r e c e i v e d a t t e n t i o n from p h y s i o l o g i s t s i n t e r e s t e d i n i t s v i s u a l s p a t i a l memory ( C o l l e t t and Land, 1975). D e s p i t e t h e wide v a r i e t y of s t u d i e s on t h i s c o s m o p o l i t a n i n s e c t , t h e r e i s s c a r c e l y any i n f o r m a t i o n a b o u t i t s p h e n o l o g y . I t u n d e r g o e s a t l e a s t two g e n e r a t i o n s p e r y e a r , one i n summer, th e o t h e r i n f a l l . M a l e s o f t h e summer g e n e r a t i o n a r e t e r r i t o r i a l , but t h o s e o f t h e autumn g e n e r a t i o n . a r e not ( W e l l i n g t o n , 1976). F e m a l e s seem t o use sperm from o n l y .1 male, and p r o b a b l y mate o n l y once ( H e a l , 1979 and F i g . 1 5 ) . Summer g e n e r a t i o n f e m a l e s o v i p o s i t 10 d a y s a f t e r emergence and l a y a s many as 3000 eggs i n 60 d a y s ( D o l l e y e t a l . , 1959). S e c o n d -g e n e r a t i o n f e m a l e s mate i n t h e autumn b e f o r e s e e k i n g w i n t e r h i b e r n a t i o n s i t e s i n c a v e s and c r e v i c e s ( K e n d a l l and S t r a d l i n g , 1972). O v a r i e s and b a s a l o o c y t e s b e g i n t o mature a f t e r a f e m a l e has been b r o u g h t out of h i b e r n a t i o n , and o v a r i e s c o n t a i n mature o o c y t e s 14 d a y s l a t e r (op. c i t . ) . F e m a l e s of t h e autumn g e n e r a t i o n l a y t h e i r f i r s t b a t c h of eggs 8-15 d a y s a f t e r h i b e r n a t i o n has been t e r m i n a t e d ( o p . c i t . ) and l a y s e v e r a l c l u s t e r s o f 100-200 eggs ( H e a l , 1979). 85 F i g u r e 14. E r i s t a l i s t e n a x and A p i s m e l l i f e r a . (a) An E. t e n a x f e m a l e . (b) A honeybee, A p i s m e l l i f e r a , f o r c o m p a r i s i o n . 86 .87 F i g u r e 15. A m a t i n g E. t e n a x p a i r . 89 In v a r i o u s l a b s t u d i e s , eggs have been r e a r e d on m o i s t human, or r a b b i t f a e c e s ( D o l l e y e t a l . , 1959, H e a l , 1979). In n a t u r e , eggs a r e u s u a l l y l a i d on p i l e s o f manure o r o t h e r d e c a y i n g o r g a n i c m a t t e r . Eggs h a t c h 2-3 d a y s a f t e r o v i p o s i t i o n . The l a r v a e , o f t e n r e f e r r e d t o as " r a t - t a i l e d " b e c a u s e o f t h e l o n g r e s p i r a t o r y p r o c e s s a t t h e i r p o s t e r i o r end, a r e s a p r o p h a g o u s i n a l l s t a g e s (Imms, 1957). Two t o t h r e e weeks a f t e r t h e l a r v a e h a t c h , t h e y p u p a t e a t t h e s u r f a c e o f t h e medium. A d u l t f l i e s emerge a f t e r 8-14 d a y s , d e p e n d i n g upon t e m p e r a t u r e ( D o l l e y e t a l . , 1959, H e a l , 1979). M a l e s and f e m a l e s a r e s i m i l a r i n a p p e a r a n c e and l e n g t h (15 mm), a l t h o u g h f e m a l e s a r e u s u a l l y d a r k e r t h a n m a l e s and have more w i d e l y s e p a r a t e d e y e s ( H e a l , 1 9 7 9 ) . B o t h s e x e s may. l i v e f o r as l o n g as 77 d a y s i n t h e l a b o r a t o r y ( D o l l e y and G o l d e n , 1947). R e s u l t s C h a r a c t e r i s t i c s o f a T e r r i t o r y M a l e s d e f e n d e d e i t h e r v e r t i c a l o r h o r i z o n t a l t e r r i t o r i e s . The f o r m e r were e s t a b l i s h e d a l o n g v e r t i c a l f a c e s of t a l l (1.5-3 m) b r o a d - l e a v e d s h r u b s ( e . g . , Rhododendron, C o t o n e a s t e r ) . R e s i d e n t m a l e s s a t on and h o v e r e d n e a r a few p a r t i c u l a r l e a v e s , a l t e r n a t e l y w a t c h i n g t h e open s p a c e away from t h e s h r u b f o r i n t r u d e r s , t h e n t u r n i n g t o i n s p e c t l e a v e s and f l o w e r s a l o n g t h e v e r t i c a l f a c e . H o r i z o n t a l t e r r i t o r i e s were e s t a b l i s h e d where c l u s t e r s o f low f l o w e r i n g p l a n t s ( e . g . , L o b e l i a , A l y s s u m , 90 Aqeratum) were i n t e r s p e r s e d w i t h p a t c h e s of open s o i l . T e r r i t o r i a l a c t i v i t y on h o r i z o n t a l t e r r i t o r i e s was c o n f i n e d t o w i t h i n 0.6 m above t h e s o i l . A r e s i d e n t m a i n t a i n e d a 360° s u r v e i l l a n c e o f t h e open s p a c e by w a t c h i n g from a s e n t r y p o s t on a l e a f o r on t h e s o i l , i n t e r m i t t e n t l y h o v e r i n g and r o t a t i n g as he d i d s o . The t y p e o f t e r r i t o r y d e f e n d e d had a major i n f l u e n c e on t h e r e s i d e n t ' s r e s p o n s e t o i n t r u d e r s ( q . v . P.100). A l l t e r r i t o r i e s i n c l u d e d b a s k i n g , g r o o m i n g , f e e d i n g , w a t c h i n g , and m a t i n g s i t e s , u s u a l l y w i t h i n an a r e a o f 0.36 m 2. M a l e s r e g u l a r l y r e t u r n e d t o one of t h e s e v e r a l s i t e s w i t h i n t h a t a r e a a f t e r e v e r y c h a s e o r i n s p e c t i o n , i n s t e a d o f r e t u r n i n g t o one o f s e v e r a l s e n t r y p o s t s a l o n g a t e r r i t o r y edge o r p a t r o l r o u t e , as d i d males of t h e b u l b - f l y s p e c i e s . O v i p o s i t i o n s i t e s ( i . e . , s t a g n a n t w a t e r a r o u n d compost heaps or manure p i l e s ) were n e v e r p a r t of a m a l e ' s t e r r i t o r y , nor were t h e y n e c e s s a r i l y even w i t h i n 1 km of i t . P a s s i n g f e m a l e s were a p p a r e n t l y a t t r a c t e d t o t e r r i t o r i e s by t h e f o o d r e s o u r c e s t h e r e i n , w h i c h m a l e s r e g u l a r l y i n s p e c t e d and d e f e n d e d . A l l t e r r i t o r i a l components were o f t e n p r e s e n t i n a r e a s as s m a l l as 0.36 m 2 i n h o r i z o n t a l t e r r i t o r i e s , and 0.22 m3 i n v e r t i c a l t e r r i t o r i e s . However, b o u n d a r i e s o f h o r i z o n t a l t e r r i t o r i e s o f t e n e x t e n d e d t o i n c l u d e an a r e a 3.6 m 2, and v e r t i c a l t e r r i t o r i e s sometimes encompassed 1.9 m 3. Home r a n g e s were much l a r g e r t h a n t e r r i t o r i e s . E. t e n a x m a l e s were r a r e l y o f f - d u t y when on t h e i r t e r r i t o r i e s , and i n s t e a d f r e q u e n t e d o f f - d u t y s i t e s a s f a r as 15 m beyond 91 t e r r i t o r i a l b o u n d a r i e s . A male o f t e n v i s i t e d s e v e r a l s u c h s i t e s w h i c h were s c a t t e r e d o v e r a home r a n g e of some 500 m 2. Home r a n g e s were a l l a p p r o x i m a t e l y t r a p e z o i d a l o r r e c t a n g u l a r b e c a u s e o f t h e c o n s t r a i n t s imposed by f i e l d o r g a r d e n b o u n d a r i e s . They a l s o i n c l u d e d l o n g s t r e t c h e s o f f e a t u r e l e s s g r o u n d ( i . e . , l awns) a c r o s s w h i c h males had t o n a v i g a t e d u r i n g t h e i r t r a v e l s between t e r r i t o r i a l and o f f - d u t y s i t e s . T e r r i t o r i a l B e h a v i o u r s The b e h a v i o u r a l r e g i m e o f a t e r r i t o r i a l male was c o n s i d e r a b l y d i f f e r e n t from t h a t o f t h e b u l b - f l y m a l e s . E. t e n a x males f r e q u e n t l y h o v e r e d , a b e h a v i o u r o n l y r a r e l y o b s e r v e d i n b u l b f l y m a l e s and, i n a d d i t i o n , t h e y employed d i f f e r e n t s p a t i a l p a t t e r n s o f t e r r i t o r i a l d e f e n s e . Whether h i s t e r r i t o r y was h o r i z o n t a l or v e r t i c a l , a t e r r i t o r i a l d r o n e f l y p o s i t i o n e d h i m s e l f a p p r o x i m a t e l y a t i t s c e n t e r . He e i t h e r c r o u c h e d or h o v e r e d a t t h i s l o c a t i o n , s c a n n i n g t h e open s p a c e above and a r o u n d him f o r i n t r u d e r s ( F i g . 1 6 ) . In b o t h t y p e s of t e r r i t o r i e s most t i m e was s p e n t w a t c h i n g from a s e n t r y p o s t ( o r b a s k i n g on d u t y , i f t e m p e r a t u r e s were m a r g i n a l ) . A s m a l l p r o p o r t i o n o f e a c h d u t y p e r i o d was a l l o c a t e d t o h o v e r i n g ( T a b l e V ) , d u r i n g which t h e male t u r n e d h i s body t h r o u g h 180° (on a v e r t i c a l t e r r i t o r y ) t o 360° (on a h o r i z o n t a l t e r r i t o r y ) . T h i s manoeuvre e n a b l e d t h e male t o s u r v e y more of h i s t e r r i t o r y t h an he c o u l d when c r o u c h e d on a l e a f . H o v e r i n g a l s o commonly f o l l o w e d c h a s i n g . F o r example, i n two males o b s e r v e d , h o v e r i n g f o l l o w e d a c h a s e 92 F i g u r e 16. An E. t e n a x male h o v e r i n g n e a r t h e c e n t e r of h i s t e r r i t o r y , w a t c h i n g f o r i n t r u d e r s . The male shown h e r e r o t a t e d t o s u r v e y b o t h t h e open s p a c e and t h e f o o d p l a n t shown ( A l y s s u m s p . ) . 93 94 T a b l e V. Time a l l o c a t i o n by a t e r r i t o r i a l E. t e n a x male. B e h a v i o u r Time a l l o c a t e d (%) p a t r o l h o v e r c h a s e c h a s e - c o n t a c t i n s p e c t watch nbask ngroom nf eed 0.02 3.60 30.30 7.30 6.00 31 .08 16.50 5.20 (o r a c h a s e - c o n t a c t ) 29 out of 35 t i m e s . In s u c h c a s e s , h o v e r i n g may s e r v e as a r e o r i e n t a t i o n p r o c e d u r e . T e r r i t o r i a l m ales r a r e l y p a t r o l l e d t h e i r t e r r i t o r i e s ; p a t r o l l i n g o c c u p i e d <1 % of a m a l e ' s t i m e ( T a b l e V ) . M a l e s a l l o c a t e d more t i m e t o i n s p e c t i n g (7.3 % ; T a b l e V ) . An i n s p e c t i n g male h o v e r e d s l o w l y o v e r and a r o u n d . t h e f l o w e r s on one or more o f t h e f o o d p l a n t s i n h i s t e r r i t o r y ( F i g . 1 7 ) . When i n s p e c t i n g f l o w e r s w i t h t u b u l a r c o r o l l a s ( e . g . , R h o d o d e n d r o n ) , m a l e s f l e w p a r t way i n t o t h e f l o w e r . S i n c e o n l y 6 out of 142 c h a s e s (4.22 %) were p r e c e d e d by i n s p e c t i o n s , i t i s u n l i k e l y t h a t i n s p e c t i o n f l i g h t s were s o l e l y c o n c e r n e d w i t h s e a r c h i n g i n t r u d e r s . R a t h e r , i n s p e c t i n g m a l e s were p r o b a b l y more c o n c e r n e d w i t h d i s c o v e r i n g f e e d i n g f e m a l e s ( s e e d i s c u s s i o n ) . A l l o b s e r v e d males e s t a b l i s h e d t e r r i t o r i e s i n a r e a s f r e q u e n t e d by f o r a g i n g b e e s ; t h e r e f o r e " c h a s e " and " c h a s e -c o n t a c t " t o o k up a l m o s t a s much o f a m a l e ' s t i m e as "nbask" and "watch" ( T a b l e V ) . Thus t h e t e r r i t o r i a l d e f e n s e p a t t e r n among 95 F i g u r e 17. E. t e n a x male on h o r i z o n t a l t e r r i t o r y . The back l e g s d a n g l e l i k e a h o n e y b e e ' s , e x c e p t when t h e i n s e c t grooms them, as shown h e r e . 97 E . t e n a x m a l e s was a c o m b i n a t i o n o f " w a t c h - i n s p e c t - w a t c h " and " w a t c h - c h a s e - w a t c h " . "Watch" was p r e e m p t e d by "nbask" when t e m p e r a t u r e s were a p p r o x i m a t e l y 17°C. H o v e r i n g w a s . a l s o an i n t e g r a l p a r t o f t e r r i t o r i a l d e f e n s e , e s p e c i a l l y d u r i n g i n s p e c t i o n f l i g h t s , s u r v e i l l a n c e o f open s p a c e , and r e o r i e n t a t i o n a f t e r c h a s i n g . V a r i a t i o n s i n T e r r i t o r i a l B e h a v i o u r P a t t e r n s j _ . S u n l i g h t and t e m p e r a t u r e T e r r i t o r i a l m ales were r a r e l y a c t i v e b e f o r e t h e m o r n i n g a i r t e m p e r a t u r e r e a c h e d 17°C, and d i d not r e m a i n a c t i v e much beyond t h e t i m e when t h e a f t e r n o o n a i r t e m p e r a t u r e f e l l below t h a t l e v e l . On c o o l , c l o u d y d a y s , t h e r e f o r e , most t e r r i t o r i e s a p p e a r e d empty, b e c a u s e t h e r e s i d e n t s were s h e l t e r i n g b e n e a t h f o l i a g e o r u n o b t r u s i v e l y b a s k i n g on any s u f f i c i e n t l y warm o b j e c t . Whenever t h e r e were a few moments of s u n l i g h t , t h e f l i e s went d i r e c t l y t o t h e n e a r e s t f l o w e r s , a t e r a p i d l y w h i l e t h e warmth l a s t e d , t h e n d i s a p p e a r e d a g a i n when i t waned. No t e r r i t o r i a l d e f e n s e a c t i v i t y o c c u r r e d u n l e s s t e m p e r a t u r e s were >17°C f o r p r o l o n g e d p e r i o d s . D u r i n g 1980, p e r i o d s o f warmth and f u l l s u n l i g h t were r a r e . More commonly, warm sunny p e r i o d s were i n t e r s p e r s e d w i t h c o o l p e r i o d s due t o h i g h f o g o r p a s s i n g a l t o s t r a t u s c l o u d s . R e s i d e n t s b a s k e d on low v e g e t a t i o n o r on t h e s o i l d u r i n g c l o u d y p e r i o d s , becoming a c t i v e o n l y when t h e sun r e t u r n e d . On warmer, s u n n i e r d a y s , r e s i d e n t m a l e s f i r s t f e d t o r e p l e t i o n b e f o r e 98 b e g i n n i n g d e f e n s e a c t i v i t i e s . The f i r s t f e e d i n g s e s s i o n was f o l l o w e d i m m e d i a t e l y by 2-3 min of g r o o m i n g , a f t e r w h i c h t h e male b a s k e d on a l e a f f o r a few moments b e f o r e a s s u m i n g t h e "watch" p o s i t i o n a t t h e t e r r i t o r y c e n t e r . Once, t e r r i t o r i a l d e f e n s e began, a r e s i d e n t ' s b e h a v i o u r depended on t h e p r e s e n c e o r a b s e n c e of s u n l i g h t and s u b s e q u e n t c h a n g e s i n r a d i a n t h e a t . When a i r t e m p e r a t u r e s were >17°C, i n f u l l s u n l i g h t , a r e s i d e n t h o v e r e d and i n s p e c t e d f r e q u e n t l y , and watched from a s e n t r y p o s t on a l e a f between c h a s e s . 2. C r o w d i n g by c o n s p e c i f i c s Changes i n b e h a v i o u r p a t t e r n s due t o c r o w d i n g were s i m i l a r t o t h o s e d e s c r i b e d f o r M. e q u e s t r i s m a l e s . Crowded m a l e s were s u b j e c t e d t o s p a t i a l c o n s t r a i n t s when t h e i r r o u t e s t o o f f - d u t y s i t e s o v e r l a p p e d a n o t h e r ' s home ran g e o r t e r r i t o r y . Thus crowded t e r r i t o r i a l m a l e s were h a r a s s e d a s t h e y a t t e m p t e d t o r e a c h t h e i r o f f - d u t y s i t e s , and, as a r e s u l t , were o f t e n p r e v e n t e d f rom g o i n g o f f - d u t y . M a l e s n o t crowded by c o n s p e c i f i c s c h a s e d a l l i n t r u d i n g b ees and f l i e s t h a t p a s s e d t h r o u g h t h e i r t e r r i t o r i e s , but r a r e l y s t r u c k one. F o r example, d u r i n g a 17 min i n t e r v a l , when 87 i n s e c t s p a s s e d t h r o u g h a r e s i d e n t ' s t e r r i t o r y , o n l y 3 ( a l l b e e s ) were s t r u c k . The r e s t , 7 c o n s p e c i f i c m a l e s , 7 s y r p h i d s , and 70 f o r a g i n g honey- and bumblebees, were m e r e l y c h a s e d t o a t e r r i t o r i a l b o u n d a r y . An uncrowded male t h a t had r e c e n t l y been o f f - d u t y would h o v e r o u t s i d e f l o w e r s c o n t a i n i n g f o r a g i n g bumblebees and w a i t 99 u n t i l t h e , b e e s emerged b e f o r e h a r r y i n g them out of t h e t e r r i t o r y . In c o n t r a s t , crowded m a l e s t h a t had been p r e v e n t e d by t h e i r n e i g h b o u r s from g o i n g o f f - d u t y would d a r t r e p e a t e d l y a t bumblebees t h a t were s t i l l i n f l o w e r s , u n t i l t h e bee s s t o p p e d c o l l e c t i n g and t r i e d t o l e a v e . But even b e f o r e a bee c o u l d f u l l y e x t r i c a t e i t s e l f , s u c h a male would s t r i k e i t from above, s e n d i n g i t t u m b l i n g >15 cm. In t h e e n s u i n g p u r s u i t , t h e male would not f e i g n a t t a c k s a s an uncrowded male would, b ut a c t u a l l y s t r u c k t h e bee r e p e a t e d l y . These crowded m a l e s would a l s o a t t a c k b u t t e r f l i e s and p o t e n t i a l p r e d a t o r s t h a t were not h a r a s s e d i n l e s s crowded c i r c u m s t a n c e s . One crowded male even p u r s u e d and a t t a c k e d a b a l d - f a c e d h o r n e t ( V e s p u l a m a c u l a t a ( L . ) ) , but somehow managed t o e s c a p e when she t u r n e d on him and a t t e m p t e d t o s t i n g . Thus i n c r e a s e d a g g r e s s i o n a r i s i n g f r o m p r o l o n g e d c o n f i n e m e n t on t h e t e r r i t o r y , [whether from c r o w d i n g by male c o n s p e c i f i c s or from o t h e r f a c t o r s , e.g., t h e l o s s of p o l a r i z e d l i g h t f r o m t h e z e n i t h ( W e l l i n g t o n , 1976)] may have p o t e n t i a l l y l e t h a l c o n s e q u e n c e s . The d e n s i t y of c o n s p e c i f i c m a l e s a l s o a f f e c t e d i n d i v i d u a l a t t e m p t s t o e s t a b l i s h t e r r i t o r i e s . O f t e n 12-18 ma l e s were seen f e e d i n g and a t t e m p t i n g t o e s t a b l i s h t e r r i t o r i e s w i t h i n a h o r i z o n t a l a r e a 1x1.5 m. C o n t a c t s between s u c h m a l e s were f r e q u e n t (up t o 18 c o n t a c t s p e r male p e r m i n ) , and o f t e n as many as f o u r m a l e s were seen p u r s u i n g and s t r i k i n g e a c h o t h e r . Under s u c h c i r c u m s t a n c e s , no male c o u l d e s t a b l i s h a t e r r i t o r y or g e t enough f o o d so t h a t , a f t e r 1 h of s u c h f r a n t i c a c t i v i t y , t h e p a r t i c i p a n t s u s u a l l y s c a t t e r e d . 100 3. T e r r i t o r y t y p e M a l e s d e f e n d i n g a v e r t i c a l t e r r i t o r y had more r e s t r i c t e d f i e l d s of view t h a n t h e i r c o u n t e r p a r t s on h o r i z o n t a l t e r r i t o r i e s . When p e r c h e d o r h o v e r i n g , t h e l a t t e r were a b l e t o see and r e a c t t o movements on e i t h e r s i d e , i n f r o n t , b e n e a t h and o v e r h e a d , whereas t h e f o r m e r s ' f i e l d of view was s e v e r e l y l i m i t e d by t h e w a l l of v e g e t a t i o n . O n l y t h e o v e r h e a d view of a male on a v e r t i c a l t e r r i t o r y was as b r o a d as h i s c o u n t e r p a r t ' s on a h o r i z o n t a l s i t e . When p a t r o l l i n g or i n s p e c t i n g , a male on a v e r t i c a l t e r r i t o r y had an even more r e s t r i c t e d f i e l d o f v i e w . As he moved c l o s e t o e a c h f l o w e r t o i n s p e c t i t , he c o u l d n ot see movements anywhere e l s e , and t h u s o n l y r e s p o n d e d t o i n t r u d e r s d i s c o v e r e d i n t h e f l o w e r s , o v e r l o o k i n g t h o s e w h i c h p a s s e d above, below, and t o e i t h e r s i d e o f him. These d i f f e r e n c e s i n a v a i l a b l e f i e l d o f view l e d t o d i f f e r e n t r e s p o n s e r a t e s , and t h e r e f o r e d i f f e r e n t l e v e l s o f a g g r e s s i v e i n t e n s i t y , among ma l e s on t h e two k i n d s of t e r r i t o r i e s . F o r example, i n one 15-min p e r i o d when t h e male was p r e s e n t , a v e r t i c a l t e r r i t o r y 2 m h i g h and 1 m wide on a f l o w e r i n g Rhododendron was v i s i t e d by 18 i n t r u d e r s : 5 honey b e e s , 8 bumblebees, 1 v e s p i d wasp, 2 a p h i d o p h a g o u s s y r p h i d s and 2 s a r c o p h a g i d s . D u r i n g t h a t p e r i o d , t h e male o c c u p i e d two d i f f e r e n t p e r c h e s f o r 6 min, i n s p e c t e d f o r 7 min, and i n t e r a c t e d f o r a t o t a l of 2 min w i t h h i s n e i g h b o u r on t h e a d j o i n i n g t e r r i t o r y and w i t h t h e i n t r u d e r s he d i s c o v e r e d . In t h o s e 2 min he had two b o u n d a r y e n c o u n t e r s w i t h h i s n e i g h b o u r , and a t o t a l of e i g h t e n c o u n t e r s w i t h i n t r u d e r s : f o u r w i t h 101 bumblebees, t h r e e w i t h honey b e e s , and one w i t h a s a r c o p h a g i d f l y . He n e v e r n o t i c e d t h e .other 10 i n t r u s i o n s , nor d i d he n o t i c e 3 b o r d e r c r o s s i n g s by h i s n e i g h b o u r , , s i n c e a l l of t h e s e t o o k p l a c e w h i l e he was i n s p e c t i n g f l o w e r s o r c h a s i n g i n d i v i d u a l i n t r u d e r s . In c o n t r a s t , i n a s i m i l a r i n t e r v a l on a h o r i z o n t a l t e r r i t o r y of c o m p a r a b l e s i z e , w h i c h was p l a n t e d w i t h low-g r o w i n g Ageratum, L o b e l i a and A l y s s u m , t h e r e were 16 v i s i t o r s (8 honey b e e s , 2 a p h i d o p h a g o u s s y r p h i d s , 2 cabbage b u t t e r f l i e s and 4 m u s c i d s ) . The r e s i d e n t male p e r c h e d f o r o n l y 2 min of t h e 15-min p e r i o d . D u r i n g t h e r e m a i n i n g 13 min, he was e i t h e r h o v e r i n g i n one o r a n o t h e r of t h e o p e n i n g s between t h e p l a n t s o r i n t e r a c t i n g w i t h t h e i n t r u d e r s o r t h e n e i g h b o u r i n g m ale. He had s e v e n b o u n d a r y e n c o u n t e r s w i t h t h e l a t t e r , and c h a l l e n g e d 13 of t h e 16 v i s i t o r s , o v e r l o o k i n g o n l y 1 bee and 2 m u s c i d s w h i c h r e s p e c t i v e l y e n t e r e d f a r c o r n e r s of t h e t e r r i t o r y w h i l e he was c h a s i n g i n t r u d e r s a t t h e o t h e r end. T h i s male o v e r l o o k e d o n l y one b o r d e r c r o s s i n g by h i s n e i g h b o u r . 4. I n s e c t age and s t a g e L i k e M. e q u e s t r i s , E. t e n a x m a l e s undergo a g r a d u a l t r a n s i t i o n f r o m d i s p e r s e r t o r e s i d e n t . A l t h o u g h I d i d n o t o b s e r v e any d r o n e s t h a t had been f o r c e d t o end t h e i r d i s p e r s a l f l i g h t s when p o l a r i z e d l i g h t waned, I d i d o b s e r v e s e v e r a l m a l e s i n t h e i r t r a n s i t i o n p e r i o d . L a t e i n t h e m o r n i n g of June 24, 1981, 20 m from an e s t a b l i s h e d t e r r i t o r i a l male, 25-30 d r o n e f l i e s ( m o s t l y m a l e s ) 102 were o b s e r v e d f e e d i n g v o r a c i o u s l y a t a clump o f d a i s i e s . They were so i n t e n t on f e e d i n g t h a t m a l e s and f e m a l e s i g n o r e d e a c h o t h e r ; o c c a s i o n a l l y a male c i r c l e d i n t h e a i r t o f e i n t a t a n o t h e r , b u t no f i g h t e n s u e d and b o t h s u b s e q u e n t l y r e t u r n e d t o f e e d i n g . T h e s e were p r e s u m a b l y m a l e s and f e m a l e s w h i c h had c o m p l e t e d t h e i r d i s p e r s a l f l i g h t s and were f e e d i n g b e f o r e e s t a b l i s h i n g t e r r i t o r i e s or s e a r c h i n g f o r o v i p o s i t i o n s i t e s , r e s p e c t i v e l y . S h o r t l y t h e r e a f t e r , s e v e r a l o f t h e s e m a l e s s t a k e d out v e r t i c a l t e r r i t o r i e s n e a r b y and, a l t h o u g h not b o r d e r i n g on e a c h o t h e r , became v e r y a g g r e s s i v e . They c h a s e d e v e r y i n t r u d e r t h a t p a s s e d , i n c l u d i n g some ( e . g . , a p h i d s and t i n y f l i e s ) n o t u s u a l l y c h a s e d by e s t a b l i s h e d , uncrowded, t e r r i t o r i a l m a l e s . T h e s e o b s e r v a t i o n s s u g g e s t t h a t m a l e s a t t h e end o f t h e i r d i s p e r s a l p e r i o d do not become t e r r i t o r i a l o r a g g r e s s i v e u n t i l t h e y have f e d s u b s t a n t i a l l y . H a v i n g done so, t h e y become v e r y a g g r e s s i v e , even when no o t h e r c o n s p e c i f i c m a l e s i n t r u d e . A g g r e s s i v e i n t e n s i t y p r e s u m a b l y d i m i n i s h e s a f t e r t h i s e s t a b l i s h m e n t p e r i o d , s i n c e no w e l l - e s t a b l i s h e d male was e v e r o b s e r v e d t o c h a s e i n t r u d e r s as s m a l l as a p h i d s ( s e e d i s c u s s i o n ) . R e c o g n i t i o n o f I n t r u d e r s T h e r e i s no doubt t h a t E. t e n a x m a l e s can d i s t i n g u i s h f e m a l e s from a l l o t h e r i n t r u d e r s . A male o c c a s i o n a l l y c l a s p e d a f e m a l e i n m i d - a i r , but more o f t e n f o l l o w e d 10-15 cm b e h i n d h e r u n t i l she l a n d e d t o bask or f e e d , t h e n h o v e r e d above he r f o r 103 s e v e r a l s e c o n d s b e f o r e s e t t l i n g t o c l a s p h e r . I f t h e f e m a l e e n t e r e d a f l o w e r w i t h a t u b u l a r c o r o l l a ( s u c h as a R h o d o d e n d r o n ) , t h e male h o v e r e d o u t s i d e u n t i l she emerged and t h e n c l a s p e d h e r . C o n s p e c i f i c m a l e s and a l i e n s s u c h as b e e s , wasps and b u t t e r f l i e s r e c e i v e d d i f f e r e n t t r e a t m e n t . No t e r r i t o r i a l male h e s i t a t e d b e f o r e s t r i k i n g a n o t h e r male, u n l e s s he had t o w a i t f o r t h e i n t r u d e r t o emerge from a f l o w e r . A l i e n s r e c e i v e d t h e same t r e a t m e n t , but s i n c e t h e y u s u a l l y f l e d when s t r u c k , t h e y d i d not become i n v o l v e d i n t h e l e n g t h y f i g h t s c h a r a c t e r i s t i c o f male-male i n t e r a c t i o n s . C o n f r o n t a t i o n s between two c o n s p e c i f i c m a l e s sometimes l a s t e d f o r 30 s w h i l e t h e two c h a s e d e a c h o t h e r back and f o r t h o v e r t h e r e s i d e n t ' s home r a n g e . C o n f r o n t a t i o n s between a r e s i d e n t and an a l i e n l a s t e d o n l y as l o n g as i t t o o k t h e a l i e n t o r e a c h a t e r r i t o r y b o u n d a r y , a l t h o u g h i t s e s c a p e was o f t e n impeded by blows from t h e r e s i d e n t . I r a r e l y o b s e r v e d any male a t t e m p t i n g t o mate w i t h a n o t h e r , even i n t h e most crowded s i t u a t i o n s . R a t h e r , m a l e s were a b l e t o d i s t i n g u i s h v a r i o u s k i n d s of i n t r u d e r s , as i l l u s t r a t e d by t h e f a c t t h a t a male o f t e n h o v e r e d o u t s i d e a f l o w e r c o n t a i n i n g a f e e d i n g f e m a l e , and c h a s e d away p o t e n t i a l c o m p e t i t o r s w h i l e he w a i t e d f o r h e r t o emerge. 104 DISCUSSION My o b s e r v a t i o n s s u p p o r t t h e h y p o t h e s e s t h a t 1) m a l e s of a l l t h r e e s p e c i e s show a s p e c i e s - s p e c i f i c l e v e l of a g g r e s s i o n w h i c h . i s i n f l u e n c e d and m o d u l a t e d by e x t e r n a l f a c t o r s and 2) t e r r i t o r i a l m a l e s do n o t a p p r o a c h a l l i n t r u d e r s with, m a t i n g i n t e n t . The o b s e r v e d d i f f e r e n c e s among p a t t e r n s of t e r r i t o r i a l b e h a v i o u r a l s o have i m p l i c a t i o n s f o r t h e t h e r m o r e g u l a t o r y c a p a b i l i t i e s and m a t i n g s t r a t e g i e s o f e a c h s p e c i e s . V a r i a t i o n i n A g g r e s s i o n A v a r i e t y of c i r c u m s t a n c e s h e i g h t e n a g g r e s s i v e i n t e n s i t y i n a l l t h r e e s p e c i e s , but t h e i n h e r e n t a g g r e s s i v e g r a d i e n t among t h e t h r e e i s a l w a y s m a i n t a i n e d . E. t u b e r c u l a t u s m a l e s a r e a l w a y s t h e l e a s t a g g r e s s i v e , whereas E. t e n a x and M. e q u e s t r i s m a l e s a r e i n h e r e n t l y more p u g n a c i o u s . A g g r e s s i v e i n t e n s i t y i n a l l t h r e e s p e c i e s i n c r e a s e s w i t h t h e d e n s i t y o f c o n s p e c i f i c s , v a r i e s w i t h i n s e c t age and s t a g e , and c e a s e s i f t e m p e r a t u r e s f a l l below a c e r t a i n c r i t i c a l l e v e l o r i f s u n l i g h t d i s a p p e a r s . A male s u b j e c t e d t o c r o w d i n g on h i s t e r r i t o r y r e s p o n d s by i n c r e a s i n g t h e f r e q u e n c y and i n t e n s i t y of p u r s u i t s . E. t u b e r c u l a t u s m a l e s , when crowded, p u r s u e d l a r g e i n t r u d e r s s u c h as f o r a g i n g l e a f c u t t e r b e e s , b ut n e v e r s t r u c k an i n t r u d i n g c o n s p e c i f i c o r a l i e n . M a l e s of t h e o t h e r two s p e c i e s r e s p o n d e d t o c r o w d i n g by i n c r e a s i n g t h e f r e q u e n c y of p u r s u i t s and c o n t a c t s w i t h i n t r u d e r s . H a b i t a t s t r u c t u r e ( t e r r i t o r y t y p e ) a f f e c t e d t h e s u s c e p t i b i l i t y o f E. t e n a x males t o c r o w d i n g : i n t r u d e r s were more e a s i l y h i d d e n by v e g e t a t i o n on a v e r t i c a l 105 t e r r i t o r y t h a n on a h o r i z o n t a l one. In a d d i t i o n , an E. t e n a x r e s i d e n t on a v e r t i c a l t e r r i t o r y where f l o w e r c o r o l l a s were t u b u l a r (e.g.,Rhododendron) became i s o l a t e d from t h e v i s u a l s t i m u l a t i o n o f i n t r u d e r s e a c h t i m e he f l e w i n t o a f l o w e r t o i n s p e c t i t . Thus an E. t e n a x male on a v e r t i c a l t e r r i t o r y n o t i c e d fewer i n t r u d e r s and was t h e r e f o r e l e s s s u s c e p t i b l e t o c r o w d i n g p r e s s u r e t h a n a d r o n e f l y male on a h o r i z o n t a l t e r r i t o r y . P a j u n e n (1966b) made s i m i l a r o b s e r v a t i o n s a b o u t t h e i n f l u e n c e of h a b i t a t s t r u c t u r e on i n t r u d e r r e c o g n i t i o n by t e r r i t o r i a l d r a g o n f l i e s . He o b s e r v e d t h a t L e u c o r r h i n i a  r u b i c u n d a m a l e s i n s p a r s e l y - v e g e t a t e d h a b i t a t s c o u l d see i n t r u d e r s a p p r o a c h i n g f o r s e v e r a l m e t e r s , b u t t h a t r e s i d e n t s o f de n s e h a b i t a t s were v i s u a l l y s h i e l d e d f r o m many i n t r u d e r s and t h e r e f o r e s p a r e d many a g g r e s s i v e i n t e r a c t i o n s i n h i g h - d e n s i t y s i t u a t i o n s . He a l s o p o s t u l a t e d t h a t c o r r e c t sex r e c o g n i t i o n may be i m p a i r e d i n dense h a b i t a t s . P a j u n e n ( o p . c i t . ) p o s t u l a t e d t h a t h a b i t a t t y p e a f f e c t e d s i t e t e n a c i t y , and t h a t s i t e t e n a c i t y was more i m p o r t a n t t h a n d r a g o n f l y d e n s i t y i n i n c r e a s i n g a g g r e s s i v e i n t e n s i t y . He o b s e r v e d t h a t a g g r e s s i v e i n t e n s i t y i n c r e a s e d o n l y t o a c e r t a i n l e v e l of p o p u l a t i o n d e n s i t y . When d e n s i t y s u r p a s s e d t h a t h i g h l e v e l , m a l e s began t o behave n o n - a g g r e s s i v e l y and e x h i b i t e d " c o n s i d e r a b l e s o c i a l t o l e r a n c e " . T h i s r e s p o n s e was not o b s e r v e d among t e r r i t o r i a l m a les of any o f t h e t h r e e s y r p h i d s p e c i e s s t u d i e d h e r e . I n c r e a s e s i n a g g r e s s i v e i n t e n s i t y were a s s o c i a t e d w i t h b o t h h i g h d e n s i t y and s i t e t e n a c i t y . The c r o w d i n g e f f e c t s of dense p o p u l a t i o n s were r a r e l y 106 c o n f i n e d t o a t e r r i t o r y . In a crowded a r e a , a t e r r i t o r i a l male was u s u a l l y h a r a s s e d on h i s t r a v e l s t o o f f - d u t y s i t e s as w e l l and, as a r e s u l t , was more l i k e l y t o r e m a i n on h i s t e r r i t o r y , where he was s u b j e c t e d , w i t h o u t r e s p i t e , t o f r e q u e n t i n t r u s i o n s . E. t e n a x and M. e q u e s t r i s b o t h became i n t e n s e l y a g g r e s s i v e when c o n f i n e d and h a r a s s e d i n t h i s manner. But E. t u b e r c u l a t u s m a l e s , w h i c h r a r e l y s o u g h t o f f - d u t y s i t e s away from t h e i r t e r r i t o r i e s , were n e i t h e r crowded nor d e p r i v e d of o f f - d u t y p e r i o d s b e c a u s e t h e y c o u l d t a k e t i m e o f f s i m p l y by t u r n i n g t o f a c e t h e w a l l o f v e g e t a t i o n b e h i n d them. Baker (1972) o b s e r v e d a c o m p a r a b l e d i f f e r e n c e i n c h o i c e o f r o o s t i n g s i t e s between two n y m p h a l i d b u t t e r f l i e s , I n a c h i s i o and A q l a i s  u r t i c a e . The f o r m e r a l w a y s l e f t i t s t e r r i t o r y and f l e w c a . 100 m t o i t s a f t e r n o o n r o o s t i n g s i t e . The l a t t e r r o o s t e d under n e t t l e s on i t s own t e r r i t o r y o r , i f i t s t e r r i t o r y d i d n o t c o n t a i n n e t t l e s , f l e w t o t h e n e a r e s t n e t t l e p a t c h t o r o o s t . M a l e s were n o n - a g g r e s s i v e a t r o o s t i n g s i t e s , o f t e n s h a r i n g a r o o s t w i t h o t h e r m a l e s . Baker d i d n o t say whether t h e m a l e s p r e v e n t e d from r e a c h i n g t h o s e s i t e s became more a g g r e s s i v e as t h e i r t e r r i t o r i a l s t a y was p r o l o n g e d . A l t h o u g h c r o w d i n g p r o v o k e d c h a n g e s i n b e h a v i o u r p a t t e r n s , s p a t i a l d e f e n s e p a t t e r n s v a r i e d l i t t l e . T e r r i t o r y s i z e d i d not s h r i n k i n r e s p o n s e t o c o n f i n e m e n t by c r o w d i n g . I n s t e a d of r e l i n q u i s h i n g p a r t s o f t h e i r t e r r i t o r i e s , m a l e s d e f e n d e d t h e i r e n t i r e t e r r i t o r i e s more a g g r e s s i v e l y , and E. t e n a x and M. e q u e s t r i s sometimes e x t e n d e d t h e i r d e f e n d e d a r e a s i n r e s p o n s e t o h a r a s s m e n t a t p r e v i o u s l y - n e u t r a l s i t e s . T hese 107 o b s e r v a t i o n s a r e i n c o n t r a s t t o B a k e r ' s - o b s e r v a t i o n s t h a t A g l a i s u r t i c a e males s h a r e t e r r i t o r i e s when t h e number o f m a l e s i s g r e a t e r t h a n t h e number of s u i t a b l e t e r r i t o r i e s ( B a k e r , 1972), but a r e s i m i l a r t o t h o s e o f P a j u n e n ( 1 9 6 4 ) . He o b s e r v e d t h a t L e u c o r r h i n i a c a u d a l i s m a l e s , when s u b j e c t e d t o f r e q u e n t i n t e r a c t i o n s i n h i g h - d e n s i t y s i t u a t i o n s , m a i n t a i n e d a t l e a s t 3-5 m between c o n t i n u o u s l y o c c u p i e d s i t e s . T h i s d i s t a n c e was v i r t u a l l y t h e same as t h e d i s t a n c e m a i n t a i n e d between m a l e s i n uncrowded s i t u a t i o n s . In d ense p o p u l a t i o n s , P a j u n e n (op. c i t . ) o c c a s i o n a l l y o b s e r v e d s h o r t e r d i s t a n c e s between s i t e s b u t , i n t h o s e c a s e s , a t l e a s t one male was q u i c k l y d i s p l a c e d and t h e s p a c i n g r e t u r n e d t o n o r m a l . I t i s not s u r p r i s i n g t h a t t e r r i t o r i a l a g g r e s s i o n v a r i e s w i t h a m a l e ' s age and s t a t e . Of more i n t e r e s t i s t h e way i n w h i c h t r a n s i t i o n s from n o n - a g g r e s s i v e ( i . e . , d i s p e r s a l ) t o a g g r e s s i v e ( i . e . , t e r r i t o r i a l ) s t a g e s o c c u r . A l t h o u g h few i n s e c t s were o b s e r v e d u n d e r g o i n g s u c h t r a n s i t i o n s (one M. e q u e s t r i s , f o u r E. t e n a x ) , t h e t r a n s i t i o n from d i s p e r s e r t o t e r r i t o r i a l r e s i d e n t was g r a d u a l and had c h a r a c t e r i s t i c s t e p s i n e a c h c a s e . F i r s t , d i s p e r s a l f l i g h t c e a s e d , and t h e male began t o f e e d v o r a c i o u s l y . Then he began t o i n t e r s p e r s e t h e f e e d i n g b o u t s w i t h b u r s t s of t e r r i t o r i a l b e h a v i o u r . In e a c h i n s t a n c e , i n i t i a l a g g r e s s i v e manoeuvers were more i n t e n s e t h a n t h o s e w h i c h o c c u r r e d a f t e r he became an e s t a b l i s h e d r e s i d e n t . In t h e e a r l y p a r t of t h i s s e q u e n c e , s e t t l i n g d r o n e - f l y males p u r s u e d a p h i d s and o t h e r t i n y i n s e c t s not n o r m a l l y p u r s u e d by e s t a b l i s h e d r e s i d e n t s . The n a r c i s s u s b u l b f l y p e r s i s t e n t l y 108 c h a s e d bumble bees t o h e i g h t s of 10 m, an a g g r e s s i v e a c t i o n n o t o b s e r v e d i n r e s i d e n t M. e q u e s t r i s m a l e s . The " o v e r l a p " between t h e end o f d i s p e r s a l and t h e o n s e t of t e r r i t o r i a l i t y was e s p e c i a l l y p r o n o u n c e d i n t h i s b u l b f l y , s i n c e he was s t i l l a c t i v e l y d i s p e r s i n g when waning p o l a r i z e d l i g h t f o r c e d him t o s t o p t r a v e l l i n g . H i s f i r s t 10 min i n t h e s t u d y a r e a were s p e n t a t t e m p t i n g t o c o n t i n u e . D u r i n g t h a t p e r i o d he f r e q u e n t l y s p i r a l l e d t o o r i e n t h i m s e l f , and made a number o f r a p i d f l i g h t s t o w a r d e a c h of t h e f o u r c o r n e r s of t h e s i t e . But t e r r i t o r i a l u r g e s a l s o became e v i d e n t . A f t e r e a c h f l i g h t o r s p i r a l , t h e f l y r e t u r n e d t o h o v e r above t h e p r o m i n e n t p a t c h of d a i s i e s on w h i c h he had f i r s t s e t t l e d . As n o t e d above, he a l s o began t o c h a s e a l l a i r b o r n e i n t r u d e r s ( m a i n l y bumble b e e s ) w i t h u n u s u a l i n t e n s i t y . Thus t h e f l y e s t a b l i s h e d an a e r i a l t e r r i t o r y even w h i l e he was s t i l l a t t e m p t i n g t o l e a v e t h e a r e a and c o n t i n u e d i s p e r s i n g . As he began t o d e l i n e a t e h i s a e r i a l b o u n d a r i e s , he a l s o began t o s e t t l e down t o f e e d v o r a c i o u s l y and t o bask , a t f i r s t o n l y b r i e f l y and t h e n f o r l o n g e r s e s s i o n s . He g r a d u a l l y began t o r e a c t , w h i l e b a s k i n g , t o a i r b o r n e i n t r u d e r s and f i n a l l y t o c r a w l i n g and f e e d i n g i n t r u d e r s . T r a c e s of t h e ur g e t o d i s p e r s e were s t i l l a p p a r e n t 37 min a f t e r he a r r i v e d i n t h e a r e a , when he i n i t i a t e d o r i e n t a t i o n s p i r a l s a g a i n i n r e s p o n s e t o c h a n g e s i n t h e p l a n e of p o l a r i z a t i o n b r o u g h t on by c i r r u s c l o u d s p a s s i n g t h r o u g h t h e z e n i t h ( W e l l i n g t o n , 1953). Such b e h a v i o u r s u g g e s t s t h a t t h e t r a n s i t i o n f r o m d i s p e r s e r t o a g g r e s s i v e r e s i d e n t i s d i r e c t e d by a " b i o l o g i c a l c l o c k " 109 mechanism w h i c h g r a d u a l l y winds down t h e " d i s p e r s e r " s t a g e w h i l e w i n d i n g up t h e " t e r r i t o r i a l a g g r e s s o r " s t a g e . Such c h a n g e s a r e common i n o t h e r a s p e c t s of i n s e c t ' s l i f e h i s t o r i e s . F o r example, t h e r e i s a c o m p a r a b l e p h y s i o l o g i c a l t r a n s i t i o n a s an i n s e c t emerges from d i a p a u s e : l o n g b e f o r e s p r i n g w e a t h e r ; b e g i n s , l e p i d o p t e r o u s pupae b e g i n t o move a b o u t i n t h e i r c o c o o n s ( D e t h i e r , 1980). And j u s t as a newly-emerged a d u l t i n s e c t r e q u i r e s some a d j u s t m e n t s t o i t s new s t a g e ( e . g . , e x p a n d i n g and d r y i n g i t s w i n g s ) , n e w l y - t e r r i t o r i a l s y r p h i d s make a d j u s t m e n t s i n t h e i r l e v e l o f a g g r e s s i o n . The newly-a r r i v e d male d r o n e f l i e s w h i c h behaved a g g r e s s i v e l y t o w a r d s t h e a p h i d s and t i n y f l i e s w h i c h e s t a b l i s h e d r e s i d e n t s would i g n o r e were making a b e h a v i o u r a l a d j u s t m e n t , as was t h e b u l b f l y w h i c h p u r s u e d bumble bees much h i g h e r t h a n e s t a b l i s h e d r e s i d e n t s . w o u l d . T h e s e a d j u s t m e n t s may be a l e a r n i n g p r o c e d u r e or r e d i r e c t e d a c t i v i t y ( L o r e n z , 1966), i n r e s p o n s e t o t h e f i r s t o n s e t of a g g r e s s i o n . The b u l b f l y ' s i n t e n s e a g g r e s s i o n may a l s o have been p a r t l y due t o h i s c o n f i n e m e n t by t h e d i s a p p e a r a n c e of z e n i t h p o l a r i z a t i o n , s u p p o r t i n g W e l l i n g t o n ' s h y p o t h e s i s t h a t s u c h c o n f i n e m e n t i n c r e a s e s t h e a g g r e s s i o n of t e r r i t o r i a l male i n s e c t s ( W e l l i n g t o n , 1976). The l e v e l of a g g r e s s i o n among ma l e s of a l l t h r e e s p e c i e s a l s o depended on s u n l i g h t and a m b i e n t t e m p e r a t u r e . Below c e r t a i n t h r e s h o l d t e m p e r a t u r e s ( c a . 20°C f o r M. e q u e s t r i s , c a . 17°C f o r E. t e n a x and E. t u b e r c u l a t u s ) , males c e a s e d t e r r i t o r i a l a c t i v i t y and b a s k e d on t h e v e g e t a t i o n ( i f t h e t e m p e r a t u r e was o n l y m a r g i n a l l y below t h e t h r e s h o l d ) o r on t h e n o s o i l ( i f t h e t e m p e r a t u r e was much l o w e r ) . . A g g r e s s i o n d i d not i n c r e a s e p r o p o r t i o n a l l y as t e m p e r a t u r e s i n c r e a s e d above t h e s p e c i e s - s p e c i f i c t h r e s h o l d . I n s t e a d , t h e t h r e s h o l d t e m p e r a t u r e seemed t o f u n c t i o n as an " o n - o f f s w i t c h " : i f t e m p e r a t u r e s were above t h e t h r e s h o l d , a g g r e s s i v e b e h a v i o u r o c c u r r e d ; i f n o t , m a l e s b a s k e d o r f e d . T h e r e a r e a l s o upper t e m p e r a t u r e t h r e s h o l d s , as d e m o n s t r a t e d by a b u l b f l y w h i c h s o u g h t shade when l e a f t e m p e r a t u r e s i n t h e s u n l i g h t r e a c h e d 3 3 ° C . F e m a l e s have l o w e r t e m p e r a t u r e t h r e s h o l d s t h a n m a l e s . F e m a l e s o f a l l t h r e e s p e c i e s were s t i l l a c t i v e l y f e e d i n g and f l y i n g d u r i n g p e r i o d s when t h e s u n l i g h t d i s a p p e a r e d o r when t e m p e r a t u r e s were t o o low f o r male t e r r i t o r i a l a c t i v i t y . D u r i n g t h e s e t i m e s , f e m a l e s b a s k e d more f r e q u e n t l y , b ut c o n t i n u e d t o be a c t i v e between b a s k i n g p e r i o d s . O t h e r w o r k e r s have o b s e r v e d sex d i f f e r e n c e s i n t e m p e r a t u r e t h r e s h o l d s ( P a j u n e n , 1966b, Buschman and P a t t e r s o n , 1981, Schone and Tengo, 1981). D i f f e r e n t t e m p e r a t u r e t h r e s h o l d s may be r e l a t e d t o t h e h i g h c o s t of male a g g r e s s i o n , t o sex d i f f e r e n c e s i n t h e mechanism of t h e r m o r e g u l a t i o n , or t o d i f f e r e n c e s i n f e e d i n g a c t i v i t y . In many s p e c i e s , f e m a l e s spend much more t i m e f e e d i n g t h a n m a l e s ( P a j u n e n , 1966b, S p i e t h , 1968, R i c h a r d s , 1982), a l t h o u g h i n t h e l a b o r a t o r y m a l e s and f e m a l e s of one s t a p h y l i n i d s p e c i e s ( T h i n o p u s p i c t u s ; R i c h a r d s , 1982) consume t h e same amount o f f o o d . T h i s i n d i c a t e s t h a t m a l e s may be " t r a d i n g o f f " f e e d i n g t i m e f o r m a t e - s e e k i n g t i m e and t h e r e f o r e do n o t have t h e e n e r g y r e s e r v e s needed t o r e m a i n a c t i v e d u r i n g c o o l or c l o u d y p e r i o d s . Thus t h e d i f f e r e n c e i n t e m p e r a t u r e t h r e s h o l d s between s e x e s may 111. be due t o t h e f a c t t h a t m a l e s f e e d l e s s and t h e r e f o r e l a c k t h e e n e r g y r e s e r v e s ( i . e . , f a t body) p r e s e n t i n f e m a l e s . The d i f f e r e n c e i n i n h e r e n t a g g r e s s i v e n e s s among t h e t h r e e s y r p h i d s r e m a i n s u n e x p l a i n e d , b u t may be due i n p a r t t o l a r v a l d e n s i t y . M. e q u e s t r i s m a l e s , a l l h i g h l y a g g r e s s i v e a s a d u l t s , s p end t h e i r l a r v a l i n s t a r s away from t h e company o f o t h e r l a r v a e , whereas l e s s - a g g r e s s i v e E . t u b e r c u l a t u s m ales a r e e x p o s e d t o c o n s p e c i f i c s d u r i n g t h e i r l a r v a l p e r i o d s ( D o u c e t t e e t a l . , 1942). N o t h i n g i s known a b o u t t h e l a r v a l d e n s i t y of E. t e n a x , however, so t h e h y p o t h e s i s t h a t l a r v a l d e n s i t y i n f l u e n c e s a d u l t a g g r e s s i o n c a n n o t be c a r r i e d beyond t h e s p e c u l a t i v e s t a g e . R e c o g n i t i o n o f F e m a l e s Kormondy (1961) wrote t h a t t h e a p p r o a c h e s of a l l male d r a g o n f l i e s t o i n t r u d e r s " a r e a p p a r e n t l y s e x u a l i n n a t u r e " , and some o t h e r w o r k e r s b e l i e v e t h a t t h e same h o l d s t r u e f o r o t h e r i n s e c t s (Moore, 1952, S c o t t , 1974, La n d and C o l l e t t , 1973, M a i e r and Wa l d b a u e r , 1979). O t h e r i n v e s t i g a t o r s , however, b e l i e v e t h a t many male i n s e c t s c an and do d i s t i n g u i s h f e m a l e s from o t h e r i n t r u d e r s b e f o r e c o n t a c t i s made ( P a j u n e n , 1964, B i c k and B i c k , 1965, B a k e r , 1972, Raw, 1975, S e v e r i n g h a u s e t a l . , 1981). J o h n s t o n (1964) p o s t u l a t e d t h a t a c c u r a t e r e c o g n i t i o n o f sex was a p r e r e q u i s i t e t o t e r r i t o r i a l a g g r e s s i o n . He assumed t h a t f a i l u r e t o r e c o g n i z e sex was t h e p r i m i t i v e c o n d i t i o n , and t h a t t h e e v o l u t i o n of t e r r i t o r i a l i t y was combined w i t h t h e d e v e l o p m e n t o f sex r e c o g n i t i o n so t h a t 112 s e x u a l r e a c t i o n s were r e l e a s e d f o r f e m a l e s o n l y . B aker (1972) o b s e r v e d t h a t male-male i n t e r a c t i o n s d i d not c e a s e when a r e s i d e n t b u t t e r f l y d i s c o v e r e d t h a t an i n t r u d e r was male, and o f f e r e d t h i s o b s e r v a t i o n as e v i d e n c e f o r t h e t h e o r y t h a t r e s i d e n t m a l e s a p p r o a c h i n t r u d e r s w i t h more t h a n m a t i n g i n t e n t . Most w o r k e r s a g r e e t h a t r e c o g n i t i o n i s p r i m a r i l y v i s u a l . I t may be b a s e d on f l i g h t p a t t e r n ( L i n , 1963) wing c o l o u r ( J a c o b s , 1955) and w i n g b e a t f r e q u e n c y ( P a j u n e n , 1964); b e h a v i o u r a l d i f f e r e n c e s and c o l o u r p a t t e r n ( I t o , 1960); o r a c o m b i n a t i o n of t h e a b ove, p l u s a pheromone t h a t a c t s a t c l o s e q u a r t e r s ( E i c k w o r t and G i n s b e r g , 1980). Even w o r k e r s who a g r e e t h a t s e x u a l r e c o g n i t i o n o c c u r s c o n c e d e t h a t t h e r e i s a v e r y c l o s e a s s o c i a t i o n o f a g g r e s s i v e and s e x u a l m o t i v a t i o n s i n t e r r i t o r i a l m a les ( J a c o b s , 1955, P a j u n e n , 1964). But o b s e r v e r s have d i f f i c u l t y i n d i s t i n g u i s h i n g between p u r e l y a g g r e s s i v e and p r e - m a t i n g a p p r o a c h e s when e a c h t y p e of p u r s u i t b e g i n s i n t h e same way and r e m a i n s v i r t u a l l y i n d i s t i n g u i s h a b l e u n t i l t h e moment of c o n t a c t . However, t h e r e i s p r o b a b l y more c o n f u s i o n i n t h e mind of t h e o b s e r v e r t h a n of t h e a g g r e s s i v e male. A l t h o u g h t h e s y r p h i d m ales s t u d i e d h e r e d i d not a l w a y s c o r r e c t l y i d e n t i f y a l l i n t r u d e r s from a d i s t a n c e , t h e y n e v e r m i s t o o k f e m a l e s f o r a n y t h i n g e l s e . T hese m a l e s sometimes c l a s p e d c o n s p e c i f i c m ales (and, l e s s o f t e n , a l i e n s ) i n b r i e f a t t e m p t s t o mate w i t h them, but f e m a l e s were n e v e r m i s t a k e n f o r m ales and d r i v e n o f f . A f e m a l e ' s . b e h a v i o u r , i n c o m b i n a t i o n w i t h v i s u a l c u e s , make i t p o s s i b l e f o r a male t o i d e n t i f y h e r . F e m a l e s n e v e r t u r n t o f a c e a male o r engage i n 113 h e a d - t o - h e a d s p i r a l s ; i n f a c t t h e y do not r e s p o n d i n any o b v i o u s manner t o h i s a p p r o a c h ( c f . P r o k o p y and Bush, 1973, S e v e r i n g h a u s e t a l . , 1981). Thus i t i s no c o i n c i d e n c e t h a t a l l i n s t a n c e s of male-male c l a s p i n g o c c u r r e d when an a g g r e s s i v e a t t a c k (and o f t e n c o n t a c t ) by t h e r e s i d e n t e l i c i t e d no r e s p o n s e from t h e i n t r u d i n g male. I t i s p o s s i b l e t h a t f e m a l e s e m i t a c l o s e - u p pheromone as do some bees ( E i c k w o r t and G i n s b e r g , 1980) w h i c h e n s u r e s t h e i r c o r r e c t i d e n t i f i c a t i o n . However, i f an i n t r u d e r s a t i s f i e s two out o f t h r e e f e m a l e s p e c i f i c a t i o n s , i . e . , l o o k s l i k e a c o n s p e c i f i c , r e s p o n d s l i k e a f e m a l e , b u t d o e s n ' t s m e l l l i k e a f e m a l e , t h e r e s i d e n t may s t i l l a t t e m p t t o mate w i t h i t . Such a t t e m p t s may be a " d e f a u l t mechanism" w h i c h would p r e v e n t t e r r i t o r i a l m a l e s from d r i v i n g f e m a l e s away, and would be e s p e c i a l l y v a l u a b l e i n a g g r e s s i v e s p e c i e s where t h e a c t of d r i v i n g f e m a l e s away by m i s t a k e would n e g a t e a l l t h e t i m e and e n e r g y a l l o t e d t o t e r r i t o r i a l d e f e n s e . O t h e r D i f f e r e n c e s Between Spec i e s In a d d i t i o n t o d i f f e r e n c e s i n a g g r e s s i o n among t h e t h r e e s p e c i e s , t h e r e a r e d i f f e r e n c e s i n b e h a v i o u r a l and s p a t i a l p a t t e r n s of t e r r i t o r i a l d e f e n s e w h i c h s u g g e s t d i f f e r e n t t h e r m o r e g u l a t o r y a b i l i t i e s and m a t i n g s t r a t e g i e s . M a l e s of b o t h s p e c i e s o f b u l b f l i e s w atched f o r i n t r u d e r s from a s e n t r y p o s t , and i n t e r m i t t e n t l y p a t r o l l e d t h e i r t e r r i t o r i e s a l o n g one of s e v e r a l r e g u l a r r o u t e s . In c o n t r a s t , d r o n e - f l y m a l e s a l l o c a t e d a l a r g e p r o p o r t i o n o f t h e i r s u r v e y p e r i o d s t o h o v e r i n g n e a r t h e c e n t e r o f t h e i r t e r r i t o r i e s . They r a r e l y p a t r o l l e d l o n g 1 14 d i s t a n c e s w i t h o u t s t o p p i n g . I n s t e a d , t h e y f l e w from p l a n t t o p l a n t or f l o w e r t o f l o w e r on t h e i r t e r r i t o r i e s , and i n s p e c t e d i n d i v i d u a l l e a v e s and f l o w e r s by h o v e r i n g i n f r o n t of them. H o v e r i n g i s a " m e t a b o l i c a l l y e x p e n s i v e " a c t i v i t y , i n w h i c h e n e r g y i s expended a t near-maximum r a t e s ( H e i n r i c h , 1979). The f a c t t h a t d r o n e f l i e s spend p r o p o r t i o n a l l y more t i m e h o v e r i n g t h a n b u l b f l i e s s u g g e s t s t h a t a) b u l b f l i e s a r e p h y s i o l o g i c a l l y i n c a p a b l e o f h o v e r i n g as o f t e n as d r o n e f l i e s , o r b) d r o n e f l i e s c a n " a f f o r d " t o expend e n e r g y a t a g r e a t r a t e , whereas b u l b f l i e s need n o t . The f i r s t s u g g e s t i o n i s u n l i k e l y , b e c a u s e M. e q u e s t r i s m a l e s a r e c e r t a i n l y c a p a b l e of h o v e r i n g f o r l o n g p e r i o d s ( s e e p . 6 0 ) , a l t h o u g h E. t u b e r c u l a t u s m a l e s may be p h y s i o l o g i c a l l y l i m i t e d by t h e i r l a r g e s u r f a c e a r e a t o volume r a t i o and l a c k of body p i l e ( H e i n r i c h and P a n t l e , 1975). The s e c o n d r a t i o n a l e i s more l i k e l y . B u l b - f l y m a l e s , w h i c h d e f e n d f e m a l e o v i p o s i t i o n s i t e s , a r e a l m o s t a s s u r e d o f t h e o p p o r t u n i t y t o mate w i t h f e m a l e s as l o n g as t h e y c o n t i n u e t o watch p o t e n t i a l o v i p o s i t i o n s i t e s on t h e i r t e r r i t o r i e s . But d r o n e f l i e s do n o t d e f e n d o v i p o s i t i o n s i t e s . They s t a k e out f o o d r e s o u r c e s and watch f o r i n c o m i n g and f e e d i n g f e m a l e s . S i n c e t h e s e f e m a l e s a r e i n c o n s p i c u o u s w h i l e t h e y s i t on l e a v e s o r f l o w e r s , t h e y a r e more l i k e l y t o be d i s c o v e r e d d u r i n g h o v e r i n g i n s p e c t i o n f l i g h t s t h a n by q u i c k p a t r o l f l i g h t s t h r o u g h t h e t e r r i t o r y ' s open s p a c e s . However, t h e d i f f e r e n c e i n t h e t y p e of s i t e d e f e n d e d does not e n t i r e l y e x p l a i n why a d r o n e f l y s h o u l d i n v e s t a g r e a t e r amount of e n e r g y ( i n terms of e n e r g y expended h o v e r i n g ) t h a n a •115 b u l b - f l y . m a le. The answer t o t h a t q u e s t i o n may l i e i n t h e c o n c e p t o f sperm p r e c e d e n c e . T h e r e i s some e v i d e n c e t h a t , i n d r a g o n f l i e s (Alcoc.k, 1979), and i n some bees ( E i c k w o r t . and G i n s b e r g , 1980), d r o s o p h i l i d s and a n t h o m y i i d s ( P a r k e r , 1970c, Bloorman and P a r k e r , 1976), s y r p h i d s ( M a i e r and W a l d b a u e r , 1979), and a c o l o e p t e r a n , s e v e r a l o r t h o p t e r a n s and l e p i d o p t e r a n s ( s e e P a r k e r , 1970c, f o r r e v i e w ) , a f e m a l e u s e s sperm from h e r l a s t m a t i n g t o f e r t i l i z e most o f h e r e g g s . O t h e r f e m a l e bees ( L i n , 1963, Raw, 1974) and f l i e s (Buschman and P a t t e r s o n , 1981) a r e monandrous and o n l y mate o n c e . The d i f f e r e n c e i n t e r r i t o r i a l d e f e n s e p a t t e r n s between b u l b - and d r o n e - f l y m a l e s may r e f l e c t t h i s . d i f f e r e n c e i n r e p r o d u c t i v e p h y s i o l o g y and may a l s o e x p l a i n t h e f a c t t h a t t e r r i t o r i a l b e h a v i o u r p a t t e r n s of d r o n e - f l y . m a l e s more c l o s e l y r e s e m b l e t h o s e of m u s c i d s t h a n of b u l b f l i e s . B u l b - f l y f e m a l e s , w h i c h mate r e p e a t e d l y , o b v i o u s l y c o u l d o b t a i n most o f t h e sperm t h e y r e q u i r e f r o m t h e l a s t male t o mate w i t h them b e f o r e t h e y o v i p o s i t . C o n s e q u e n t l y , i t would be a u s e f u l t a c t i c f o r b u l b -f l y m a l e s t o d e f e n d o v i p o s i t i o n s i t e s . D r o n e - f l y f e m a l e s a p p a r e n t l y o n l y mate once ( H e a l , 1979). Thus i t would be w o r t h w h i l e f o r d r o n e - f l y m a l e s t o d e f e n d r e s o u r c e s v i s i t e d by newly-emerged f e m a l e s and t o expend t h e i r e n e r g y h o v e r i n g i n o r d e r t o maximize t h e i r c h a n c e s of m a t i n g w i t h v i r g i n f e m a l e s . 1 16 IMPLICATIONS FOR AGRICULTURE : T e r r i t o r i a l males of a l l t h r e e s p e c i e s , p a r t i c u l a r l y M. e q u e s t r i s and E. t e n a x , a r e c a p a b l e o f d i s r u p t i n g t h e f o r a g i n g p a t h s of p o l l i n a t o r s and b i o l o g i c a l c o n t r o l a g e n t s . I o f t e n o b s e r v e d males of t h e two more a g g r e s s i v e s y r p h i d a p e c i e s s t r i k i n g a i r b o r n e and f o r a g i n g bees w i t h . e n o u g h f o r c e t o knock them t o t h e g r o u n d , and r e p e a t i n g t h e manoeuver as t h e s t u n n e d bees a t t e m p t e d t o f l y away ( a l s o see S e v e r i n g h a u s e t a l . , 1981). E. t e n a x males o f t e n h o v e r e d o u t s i d e f l o w e r s c o n t a i n i n g f o r a g i n g b e e s , t h e n s t r u c k them r e p e a t e d l y as t h e y emerged w i t h t h e i r p o l l e n l o a d s . W e l l i n g t o n (1976) r e p o r t e d t h a t bees h a r a s s e d i n t h i s f a s h i o n q u i c k l y l e a r n t o a v o i d s y r p h i d t e r r i t o r i e s , a f a c t w h i c h i s n o t s u r p r i s i n g i n view o f t h e mnemonic c a p a c i t y of b e e s , p a r t i c u l a r l y h o n e y b e e s (von F r i s c h , 1971, W e l l i n g t o n and C m i r a l o v a , 1979). S i m i l a r l y , a g g r e s s i v e s y r p h i d m a l e s a r e c a p a b l e o f e x c l u d i n g o t h e r l e s s - a g g r e s s i v e s y r p h i d s p e c i e s . In f a c t , t h e U.B.C. f i e l d s i t e u s e d i n t h i s s t u d y was o r i g i n a l l y i n t e n d e d f o r use i n o v i p o s i t i o n b e h a v i o u r s t u d i e s i n v o l v i n g a p h i d o p h a g o u s s y r p h i d f e m a l e s . However, a g g r e s s i v e E. t e n a x m a l e s d r o v e v i r t u a l l y a l l a p h i d o p h a g o u s s y r p h i d s from t h e p l o t . Sometimes as few as f o u r t e r r i t o r i a l m a l e s b l o c k e d a l l e n t r a n c e r o u t e s t o t h e 7 x 8 m p l o t by d e f e n d i n g 1 x 2 m t e r r i t o r i e s i n e a c h o f i t s c o r n e r s . Such t e r r i t o r i a l m a l e s c o u l d c o n t r i b u t e t o a p h i d p o p u l a t i o n o u t b r e a k s by p r e v e n t i n g o v i p o s i t i o n of o t h e r s p e c i e s o f s y r p h i d s and s u b s e q u e n t emergence of a p h i d o p h a g o u s l a r v a e . 117 AREAS FOR FUTURE STUDY The work p r e s e n t e d h e r e i s a b e g i n n i n g and r a i s e s more q u e s t i o n s t h a n i t a n s w e r s . More i n f o r m a t i o n can be g a i n e d a b o u t t h e t e r r i t o r i a l male as a d e c i s i o n - m a k e r by a t t e m p t i n g t o d i s c o v e r how t i g h t l y t h e o b s e r v e d v a r i a t i o n i n a g g r e s s i v e i n t e n s i t y i s l i n k e d t o i n h e r i t a n c e , l a r v a l c o n d i t i o n s , e n e r g y b u d g e t i n g , and sperm p r e c e d e n c e . I n h e r i t a n c e seems t o c o n t r i b u t e s u b s t a n t i a l l y t o t h e t e r r i t o r i a l a g g r e s s i v e n e s s of m ales of t h e t h r e e s p e c i e s s t u d i e d h e r e , but i s a d i f f i c u l t p a r a m e t e r t o q u a n t i f y and s t u d y ( a l s o see K i n g , 1973). T h e r e f o r e , I s u g g e s t t h a t t h e o t h e r t h r e e p a r a m e t e r s be e x p l o r e d f i r s t . The e f f e c t of l a r v a l d e n s i t y on a d u l t a g g r e s s i o n c o u l d be s t u d i e d i n t h e l a b o r a t o r y by r e a r i n g l a r v a e of e a c h of t h e t h r e e s p e c i e s a t d i f f e r e n t d e n s i t i e s and m o n i t o r i n g t h e a g g r e s s i v e b e h a v i o u r of t h e r e s u l t i n g a d u l t s . T e r r i t o r i a l b e h a v i o u r has not been i n v e s t i g a t e d i n t h e l a b o r a t o r y , but a d u l t m ales would p r o b a b l y behave t e r r i t o r i a l i t y i f t h e y were r e l e a s e d i n a w a l k - i n chamber o r r e a r i n g room t h a t had been a r r a n g e d t o mimic a f l o w e r bed, w i t h a n a t u r a l l i g h t s o u r c e . Newly-emerged a d u l t s s h o u l d be a l l o w e d t o f l y i n a wind t u n n e l u n t i l t h e y e x h a u s t t h e i r d i s p e r s a l u r g e , s i n c e t h i s s t u d y i n d i c a t e s t h a t m ales do n o t become t e r r i t o r i a l u n t i l t h e y have d i s p e r s e d . E n e r g y - b u d g e t i n g and t h e r m o r e g u l a t o r y d i f f e r e n c e s between m a l e s and f e m a l e s c o u l d be s t u d i e d by c o m p a r i n g f o o d i n t a k e and f a t body d e p o s i t i o n of f i e l d a n i m a l s w i t h t h o s e of l a b o r a t o r y -118 r e a r e d a n i m a l s t o see i f males and f e m a l e s consume d i f f e r e n t amounts of f o o d i n e i t h e r t h e l a b o r a t o r y o r t h e f i e l d . [ E . t e n a x m a l e s a r e a p p a r e n t l y c a p a b l e of s t o r i n g e n e r g y as f a t body s i n c e t h e y have been f o u n d h i b e r n a t i n g i n c a v e s w i t h o v e r w i n t e r i n g f e m a l e s ( K e n d a l l and S t r a d l i n g , 1972).] By a l l o w i n g m a l e s and f e m a l e s t o f l y f r e e l y i n a l a b o r a t o r y o r wind t u n n e l and m o n i t o r i n g c h a n g e s i n body t e m p e r a t u r e w i t h f l i g h t a c t i v i t y , one c o u l d q u a n t i f y e n e r g y e x p e n d i t u r e d u r i n g f l i g h t i n o r d e r t o d i s c e r n s e x - r e l a t e d t h e r m o r e g u l a t o r y d i f f e r e n c e s . M o n i t o r i n g c h a n g e s i n body t e m p e r a t u r e of i n a c t i v e i n s e c t s w i t h c h a n g e s i n ambient a i r t e m p e r a t u r e would a l s o e l u c i d a t e p r e s e n c e o r a b s e n c e o f s u c h d i f f e r e n c e s . I t w o u l d a l s o be u s e f u l t o q u a n t i f y t h e e n e r g y r e q u i r e m e n t s of male a g g r e s s i o n , s i n c e t h i s s t u d y and o t h e r s (see p ) have shown t h a t m a l e s r e q u i r e a h i g h e r ambient a i r t e m p e r a t u r e f o r a c t i v i t y t h a n f e m a l e s , and b e c a u s e n o n - a g g r e s s i v e S y r p h u s m a l e s c a n and do f l y a t ambient t e m p e r a t u r e s of 10°C o r l e s s ( H e i n r i c h and P a n t l e , 1975). H e i n r i c h and P a n t l e (op. c i t . ) have shown t h a t f l i e s o f th e genus S y r p h u s r e g u l a t e t h e i r t h o r a c i c t e m p e r a t u r e t h r o u g h a c o m b i n a t i o n o f b a s k i n g and s h i v e r i n g . T h e r m o r e g u l a t i o n e x p e r i m e n t s s u c h as t h o s e d e s c r i b e d above m i g h t a l s o e l u c i d a t e d i f f e r e n c e s i n b a s k i n g and s h i v e r i n g between s p e c i e s and e x p l a i n why E. t e n a x males a r e a b l e t o spend so much t i m e h o v e r i n g . E. t u b e r c u l a t u s m a l e s , w h i c h l a c k body p i l e and have a l a r g e s u r f a c e a r e a t o volume r a t i o , may r e l y , on b a s k i n g more t h a n s h i v e r i n g and t h e r e f o r e s pend more time c l o s e t o t h e s o i l 119 where t e m p e r a t u r e s a r e u s u a l l y s e v e r a l d e g r e e s warmer, t h a n t h e a i r 20 cm a b o v e . The h i g h - p i t c h e d whine h e a r d among M. e q u e s t r i s m ales may be c o r r e l a t e d w i t h warm-up by s h i v e r i n g , a s s u g g e s t e d by H e i n r i c h and P a n t l e (op. c i t . ) . E n e r g y - b u d g e t i n g e x p e r i m e n t s , combined w i t h i r r a d i a t i o n e x p e r i m e n t s (as p e r Blo o r m a n • a n d P a r k e r , 1976) t o see whether sperm p r e c e d e n c e o c c u r s i n M. e q u e s t r i s and E. t u b e r c u l a t u s but not i n E. t e n a x , would p r o v i d e p a r t i a l e x p l a n a t i o n s f o r v a r i a t i o n s i n b e h a v i o u r p a t t e r n s and a g g r e s s i v e i n t e n s i t y among s p e c i e s . R e s u l t s o f l a b e x p e r i m e n t s , i n c o n j u n c t i o n w i t h p a t t e r n - r e c o g n i t i o n t e c h n i q u e s ( s u c h as t h e s t r e a k p r o g r a m d e s c r i b e d i n M a t e r i a l s and Methods) a p p l i e d t o a l a r g e r d a t a b a s e , would f u r t h e r u n d e r s t a n d i n g of d e c i s i o n s made by t e r r i t o r i a l male s y r p h i d s . 1 20 LITERATURE CITED A l c o c k , J . 1975. T e r r i t o r i a l b e h a v i o r by m a l e s o f P h i l a n t h u s  m u l t i m a c u l a t u s w i t h a r e v i e w of t e r r i t o r i a l i t y i n male s p h e c i d s . Anim. Behav. 23:889-895. A l c o c k , J . 1976. The s o c i a l o r g a n i z a t i o n of male p o p u l a t i o n s o f C e n t r i s p a 1 1 i d a (Hymenoptera, A n t h o p h o r i d a e ) . P s y c h e 83: 121-131. A l c o c k , J . 1979. M u l t i p l e m a t i n g i n C a l y o p t e r i x m a c u l a t a ( O d o n a t a : C a l y o p t e r i d a e ) and t h e a d v a n t a g e of n o n - c o n t a c t g u a r d i n g by m a l e s . J . N a t . H i s t . 13:439-446. A l c o c k , J . , E.M. B a r r o w s , G. Gordh, L . J . Hubbard, L. K i r k e n d a l l , D.W. P y l e , T.L. P o n der, and F.G. Zalom. 1978. The e c o l o g y and e v o l u t i o n of male r e p r o d u c t i v e b e h a v i o u r i n t h e bees and wasps. J . L i n n . Soc. London Z o o l . 64:293-326. A l e x a n d e r , R.D. 1961. A g g r e s s i v e n e s s , t e r r i t o r i a l i t y and s e x u a l b e h a v i o u r i n f i e l d 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 ) . Behav. 17:131-214. A l i N i a z e e , M.T. 1974. The w e s t e r n c h e r r y f r u i t f l y , R h a g o l e t i s  i n d i f f e r e n s ( D i p t e r a : T e p h r i t i d a e ) . 2. A g g r e s s i v e b e h a v i o u r . Can. E n t . 106:1201-1204. A l t e r , D., and-E.H. Cleminshaw. 1956. P i c t o r i a l A s t r o n o m y . C r o w e l l , New Y o r k . 310 pp. B a k e r , R.R. 1972. T e r r i t o r i a l b e h a v i o r o f t h e n y m p h a l i d b u t t e r f l i e s , A g l a i s u r t i c a e ( L . ) and I n a c h i s i o ( L . ) . J . anim. E c o l . 41:453-469. B a r r o w s , E.M. 1976. M a t i n g b e h a v i o r i n h a l i c t i n e b e e s . I I . M i c r o t e r r i t o r i a l and p a t r o l l i n g b e h a v i o r of m a l e s o f L a s i o g l o s s u m r o h w e r i . Z. T i e r p s y c h o l . 40:377-389. 121 B i c k , G.H., and J.C. B i c k . 1965. Demography and b e h a v i o r i n t h e d a m s e l f l y , A r g i a a p i c a l i s ( S a y ) , ( O d o n a t a : C o e n a g r i i d a e ) . E c o l o g y 46:461-472. B i g g s , J.D. 1972. A g g r e s s i v e b e h a v i o r i n t h e a d u l t a p p l e maggot ( D i p t e r a : T e p h r i t i d a e ) . Can. E n t . 104:349-353. B l i c k l e , R.L. 1959. O b s e r v a t i o n s on t h e h o v e r i n g and m a t i n g o f Tabanus b i s h o p p i S t o n e ( D i p t e r a : T a b a n i d a e ) . Ann. e n t . Soc. Am. 52:183-190. Bl o o r m a n , E . , and G.A. P a r k e r . 1976. Sperm ( e j a c u l a t e ) c o m p e t i t i o n i n D r o s o p h i l a m e l a n o g a s t e r , and t h e r e p r o d u c t i v e v a l u e o f f e m a l e s t o m a l e s i n r e l a t i o n t o f e m a l e age and m a t i n g s t a t u s . J . e c o l . E n t . j _ : 145-155. Boyce, A.M. 1934. B i o n o m i c s o f t h e w a l n u t husk f l y , R h a q o l e t i s  c o m p l e t a . H i l g a r d i a 8:363-579. In B i g g s , J.D. 1972. i b i d . B r o a d b e n t , B.M. 1927. F u r t h e r o b s e r v a t i o n s on t h e l i f e h i s t o r y , h a b i t s and c o n t r o l o f t h e n a r c i s s u s b u l b f l y , Merodon  e q u e s t r i s , w i t h d a t a on t h e e f f e c t s of c a r b o n d i s u l p h i d e f u m i g a t i o n on t h r e e b u l b p e s t s . J . e c o n . E n t . 20:94-113. Brower, L.V.Z., and L. Brower. 1965. E x p e r i m e n t a l s t u d i e s of m i m i c r y . 8. F u r t h e r i n v e s t i g a t i o n s of h o n e y b e e s ( A p i s  m e l l i f e r a ) and t h e i r d r o n e f l y m i m i c s ( E r i s t a l i s s p p . ) . Am. N a t . 99:173-187. Brown, J . L . , and G.H. O r i a n s . 1970. S p a c i n g p a t t e r n s i n m o b i l e a n i m a l s . Ann. Rev. E c o l . S y s t . J_:239~262. Buschman, L . L . , and R.S. P a t t e r s o n . 1981. A s s e m b l y , m a t i n g , and t h e r m o r e g u l a t i n g b e h a v i o r of s t a b l e f l i e s under f i e l d c o n d i t i o n s . Env. E n t . 10 :16-21. C a t t s , E.P. 1979. H i l l t o p a g g r e g a t i o n and m a t i n g b e h a v i o u r o f G a s t e r o p h i l u s i n t e s t i n a l i s ( D i p t e r a : G a s t e r o p h i l i d a e ) . J . med. E n t . 16:461-464. 1 22 C a z i e r , M.A., and E.G. L i n s l e y . 1963. T e r r i t o r i a l b e h a v i o u r among.males of P r o t o x e a g l o r i o s a ( A n d r e n i d a e ) . Can. E n t . 95:547-556. C o l l e t t , T.S., and M.F. L a n d . 1975. V i s u a l s p a t i a l memory i n a h o v e r f l y . J . comp. P h y s i o l . 100:59-84. C o l v i l l e , R.E., and P.L. C o l v i l l e . 1980. N e s t i n g b i o l o g y and male b e h a v i o r o f T r y p o x y l o n ( T r i p a r q i l u m ) t e n o c t i t l a n i n C o s t a R i c a (Hymenoptera: S p h e c i d a e ) . Ann. e n t . Soc. Am. 73:110-119. D a v i e s , N.B. 1978a. E c o l o g i c a l q u e s t i o n s a b o u t t e r r i t o r i a l b e h a v i o u r , pp. 317-350 _in J.R. K r e b s and N.B. D a v i e s ( E d s . ) , B e h a v i o u r a l E c o l o g y : An E v o l u t i o n a r y A p p r o a c h . B l a c k w e l l S c i e n t i f i c , O x f o r d . D a v i e s , N.B. 1978b. T e r r i t o r i a l d e f e n s e i n t h e s p e c k l e d wood b u t t e r f l y ( P a r a g e a e g e r i a ) : The r e s i d e n t a l w a y s w i n s . Anim. Behav. 26:.138-147. D e t h i e r , V.G. 1980. The W o r l d of t h e T e n t - m a k e r s . A N a t u r a l H i s t o r y of t h e E a s t e r n T e n t C a t e r p i l l a r . U n i v . o f M a s s a c h u s e t t s P r e s s , Amherst. 148 pp. D o l l e y , W.L., and L.H. G o l d e n . 1947. The e f f e c t o f sex and age on t h e t e m p e r a t u r e a t w h i c h r e v e r s a l i n r e a c t i o n t o l i g h t i n E r i s t a l i s t e n a x o c c u r s . B i o l . B u l l . 92:178-186. D o l l e y , W.L., C C . H a s s e t t , W.B. Bowen, and G. P h i l l i e s . 1959. C u l t u r e of t h e d r o n e f l y , E r i s t a l i s t e n a x . pp. 410-411 iri J.G. Needham ( E d . ) , C u l t u r e Methods f o r I n v e r t e b r a t e A n i m a l s . D o v e r , New Y o r k . D o u c e t t e , C.F., R. L a t t a , C H . M a r t i n , R. Schopp, and P.M. E i d e . 1942. The b i o l o g y o f t h e n a r c i s s u s b u l b f l y i n t h e P a c i f i c N o r t h w e s t . U.S.D.A. T e c h . B u l l . 809:1-66. E i c k w o r t , G . C 1977. Male t e r r i t o r i a l b e h a v i o r i n t h e mason bee H o p l i t i s a n t h o c o p o i d e s (Hymenoptera: M e g a c h i l i d a e ) . Anim. Behav. 25:542-554. 1 23 E i c k w o r t , G.C., and H.S. G i n s b e r g . 1980. F o r a g i n g and m a t i n g b e h a v i o r i n A p o i d e a . Ann. Rev. E n t . 25:421-426. Ewing, L.S. 1967.. F i g h t i n g and d e a t h from s t r e s s i n a c o c k r o a c h . S c i e n c e 155:1035-1036. Ewing, L.S. 1972. H i e r a r c h y and i t s r e l a t i o n t o t e r r i t o r y i n t h e c o c k r o a c h Nauphoeta c i n e r e a . Behav. 42:152-174. Ewing, L.S. 1973. T e r r i t o r i a l i t y and t h e i n f l u e n c e of f e m a l e s on t h e s p a c i n g o f m a l e s i n t h e c o c k r o a c h , N auphoeta  c i n e r e a . Behav. 45:282-303. F u j i s a k i , K. 1980. S t u d i e s on t h e m a t i n g s y s t e m o f t h e w i n t e r c h e r r y bug, A n t h o c o r i s s o r d i d u s T h u n b e r g ( H e t e r o p t e r a : C o r e i d a e ) . I . S p a t i o - t e m p o r a l d i s t r i b u t i o n . p a t t e r n of a d u l t s . Res. p o p u l . E c o l . 21:317-331. G e t t y , T. 1981. T e r r i t o r i a l b e h a v i o u r o f e a s t e r n chipmunks (Tamias s t r i a t u s ) : e n c o u n t e r a v o i d a n c e a n d s p a t i a l t i m e -s h a r i n g . E c o l o g y 62:915-921. G r u h l , K. 1924. P a a r u n g s g e w o h n h e i t e n d e r D i p t e r e n . Z. W i s s . Z o o l . 122:205-280. In M a i e r , C.T., and G.P. W a l d b a u e r . 1979. D u a l m a t e - s e e k i n g s t r a t e g i e s i n male s y r p h i d f l i e s ( D i p t e r a : S y r p h i d a e ) . Ann. e n t . Soc. Am. 72:54-61. Gwynne, D.T., and K.M. O ' N e i l l . 1980. T e r r i t o r i a l i t y i n d i g g e r wasps r e s u l t s i n s e x - b i a s e d p r e d a t i o n on m a l e s (Hymenoptera: S p h e c i d a e , P h i l a n t h u s ) . J . Rans. e n t . Soc. 53:220-224. Hagen, K.S. 1962. B i o l o g y and e c o l o g y of p r e d a c e o u s C o c c i n e l l i d a e . Ann. Rev. E n t . 7:289-326. H e a l , J . 1979. C o l o u r p a t t e r n s o f S y r p h i d a e : I . G e n e t i c v a r i a t i o n i n t h e d r o n e f l y E r i s t a l i s t e n a x . H e r e d i t y 42: 223-236. H e i n r i c h , B. 1979. Bumblebee E c o n o m i c s . H a r v a r d U n i v . P r e s s , Mass. 245 pp. 124 H e i n r i c h , B., and C. P a n t l e . 1975. T h e r m o r e g u l a t i o n i n s m a l l f l i e s ( S y r p h u s s p p . ) : b a s k i n g and s h i v e r i n g . J . exp. B i o l . 62:599-610. H e n d r i c k s , D.P. 1974. " A t t a c k s " by P o l y g o n i a i n t e r r o g a t i o n i s ( N y m p h a l i d a e ) on chimney s w i f t s and i n s e c t s . J . l e p i d . S o c . 2_8: 236. Hodson, W.E.H. 1927. The b i o n o m i c s o f t h e l e s s e r b u l b f l i e s , Eumerus s t r i q a t u s , F l y n . , and Eumerus t u b e r c u l a t u s Rond., i n s o u t h - w e s t E n g l a n d . B u l l . e n t . Res. 17:373-384. Hodson, W.E.H. 1932. The l a r g e n a r c i s s u s f l y , Merodon e q u e s t r i s , F ab. ( S y r p h i d a e ) . B u l l . e n t . Res. 23:429-448. H o l l o w a y , B.A. 1976. P o l l e n f e e d i n g i n h o v e r f l i e s ( D i p t e r a : S y r p h i d a e ) . N.Z. J . Z o o l . 3:339-350. H u x l e y , J . S . 1934. A n a t u r a l e x p e r i m e n t on t h e t e r r i t o r i a l i n s t i n c t . B r i t i s h B i r d s 27:270-277. Imms, A.D. 1957. Imms' G e n e r a l T e x t b o o k of E n t o m o l o g y . 9 t h E d . Rev. by O.W. R i c h a r d s and R.G. D a v i e s . Methuen, London. 886 pp. I t o , Y. 1960. T e r r i t o r i a l i s m and r e s i d e n t i a l i t y i n a d r a g o n f l y , O r t h e t r u m a l b i s t y l u m s p e c i o s u m U h l e r ( O d o n a t a : A n i s o p t e r a ) . Ann. e n t . S o c . Am. 53:851-853. J a c o b s , M.E. 1955. S t u d i e s on t e r r i t o r i a l i s m and s e x u a l s e l e c t i o n i n d r a g o n f l i e s . E c o l o g y 36:566-586. J a n s s o n , A. 1973. S t r i d u l a t i o n and i t s s i g n i f i c a n c e i n t h e genus C e n o c o r i x a ( H e m i p t e r a , C o r i x i d a e ) . Behav. 46:1-36. J a y c o x , E.R. 1967. T e r r i t o r i a l b e h a v i o r among m a l e s of A n t h i d i u m b a n n i n g e n s e (Hymenoptera: M e g a c h i l i d a e ) . J . Kans. e n t . Soc. 40:565-570. 125 J o h n s o n , C. 1962. A d e s c r i p t i o n o f t e r r i t o r i a l b e h a v i o r and a q u a n t i t a t i v e s t u d y of i t s f u n c t i o n i n males of H e t a e r i n a  a m e r i c a n a ( F a b r i c u s ) ( O d o n a t a : A g r i i d a e ) . Can. E n t . 94: 178-190. J o h n s o n , C. 1964. The e v o l u t i o n of t e r r i t o r i a l i t y i n t h e O d o n a t a . E v o l u t i o n 18:89-92. J o h n s o n , C.G. 1969. M i g r a t i o n and D i s p e r s a l o f I n s e c t s by F l i g h t . Methuen, London. .763 pp. Kaufman, J.H. 1971. The use of s p a c e by a n i m a l s and man. pp. 36-39 j^n A.H. E s s e r ( E d . ) , B e h a v i o u r and E n v i r o n m e n t . Plenum P r e s s , New Y o r k . K e n d a l l , D.A., and D . J . S t r a d l i n g . 1972. Some o b s e r v a t i o n s on o v e r w i n t e r i n g o f t h e d r o n e f l y , E r i s t a l i s t e n a x L. E n t o m o l o g i s t 105:229-230. K i n g , J.A. 1973. The e c o l o g y o f a g g r e s s i v e b e h a v i o r . Ann. Rev. E c o l . S y s t . 4:117-138. Kormondy, E . J . 1961. T e r r i t o r i a l i t y and d i s p e r s a l i n d r a g o n f l i e s ( O d o n a t a ) . J . N.Y. E n t . Soc. 69:42-52. La n d , M.F.., and C o l l e t t , T.S. 1974. C h a s i n g b e h a v i o u r of h o u s e f l i e s ( F a n n i a c a n n i c u l a r i s ) . A d e s c r i p t i o n and a n a l y s i s . J . comp. P h y s i o l . 89:331-357. L e y h a u s e n , P. 1968. Dominance and t e r r i t o r i a l i t y a s complemented i n mammalian s o c i a l s t r u c t u r e , pp. 22-34 _in A.H. E s s e r ( E d . ) , 1971, B e h a v i o u r and E n v i r o n m e n t . Plenum P r e s s , New Y o r k . L i n , N. 1963. T e r r i t o r i a l b e h a v i o u r i n t h e c i c a d a k i l l e r wasp, S p h e c i u s s p e c i o s u s ( D r u r y ) (Hymenoptera: S p h e c i d a e ) . P a r t I . Behav. 20:115-133. L o r e n z , K. 1966. On A g g r e s s i o n . Bantam Books, New Y o r k . 308 pp. 126 L y o n , J'.-P. 1973. La mouche des n a r c i s s e s (Merodon e q u e s t r i s F., D i p t e r e : S y r p h i d a e ) . I . I d e n t i f i c a t i o n de l ' i n s e c t e e t de s e s d e g a t s e t b i o l o g i e dans l e s u d - e s t de l a F r a n c e . Rev. Z o o l . A g r i c . P a t h o l . Veg. 2 : 6 5 _ 9 2 « MacKinnon, J . 1970. I n d i c a t i o n s o f t e r r i t o r i a l i t y i n m a n t i d s . Z. T i e r p s y c h o l . 27:150-155. M a i e r , C.T., and G.P. W a l d b a u e r . 1979. D u a l m a t e - s e e k i n g s t r a t e g i e s i n male s y r p h i d f l i e s ( D i p t e r a : S y r p h i d a e ) . Ann. e n t . Soc. Am. 72:54-61. Moore, N.W. 1952. On t h e s o - c a l l e d " t e r r i t o r i e s " o f d r a g o n f l i e s ( O d o n a t a - A n i s o p t e r a ) . Behav. 4:85-101. Moore, N.W. 1964. I n t r a - and i n t e r - s p e c i f i c c o m p e t i t i o n among d r a g o n f l i e s ( O d o n a t a ) . J . anim. E c o l . 33:49-71 . N i c e , M.M. 1941. The r o l e o f t e r r i t o r y i n b i r d l i f e . Am. m i d l . N a t . 26:441-487. N o b l e , G.K. 1939. Symposium on t h e i n d i v i d u a l v s . t h e s p e c i e s . IV. The r o l e of dominance i n t h e s o c i a l l i f e o f b i r d s . Auk 56:263-273. O l d r o y d , H. 1965. The N a t u r a l H i s t o r y of F l i e s . W.W. N o r t o n and Co., New Y o r k . 348 pp. O t t e , D., and A. J o e r n . 1975. I n s e c t t e r r i t o r i a l i t y and i t s e v o l u t i o n : p o p u l a t i o n s t u d i e s o f d e s e r t g r a s s h o p p e r s on c r e o s o t e b u s h e s . J . anim. E c o l . 44:29-54. P a j u n e n , V . I . 1964. A g g r e s s i v e b e h a v i o r i n L e u c o r r h i n i a c a u d a l i s C h a r p . ( O d o n a t a : L i b e l l u l i d a e ) . Ann. Z o o l . Fenn. 1:357-369. P a j u n e n , V . I . 1966a. A g g r e s s i v e b e h a v i o r and t e r r i t o r i a l i t y i n a p o p u l a t i o n of C a l y o p t e r i x v i r g o L. ( O d o n a t a : C a l y o p t e r y g i d a e ) . Ann. Z o o l . F e n n . 3_i2v\-2\4. 1 27 P a j u n e n , V . I . 1966b. The i n f l u e n c e o f p o p u l a t i o n d e n s i t y on t h e t e r r i t o r i a l b e h a v i o r of L e u c o r r h i n i a r u b i c u n d a L. ( O d o n a t a : L i b e l l u l i d a e ) . Ann. Z o o l . F e n n . 3:40-52. P a r k e r , G.A. 1970a. The r e p r o d u c t i v e b e h a v i o u r and t h e n a t u r e of s e x u a l s e l e c t i o n i n S c a t o p h a g a s t e r c o r i a L. ( D i p t e r a : S c a t o p h a g i d a e ) . I I . The f e r t i l i z a t i o n r a t e and t h e s p a t i a l and t e m p o r a l r e l a t i o n s h i p s of e a c h sex a r o u n d t h e s i t e o f m a t i n g and o v i p o s i t i o n . J . anim. E c o l . 39:205-228. P a r k e r , G.A. 1970b. The r e p r o d u c t i v e b e h a v i o u r and t h e n a t u r e of s e x u a l s e l e c t i o n i n S c a t o p h a g a s t e r c o r a r i a L. ( D i p t e r a : ScatophagidaeT! IV. E p i g a m i c r e c o g n i t i o n and c o m p e t i t i o n between m a l e s f o r the p o s s e s s i o n o f f e m a l e s . Behav. 37:113-139. P a r k e r , G.A. 1970c. Sperm c o m p e t i t i o n and i t s e v o l u t i o n a r y c o n s e q u e n c e s i n i n s e c t s . B i o l . Rev. 45:525-567. P a r k e r , G.A. 1978. E v o l u t i o n o f c o m p e t i t i v e mate s e a r c h i n g . Ann. Rev. E n t . 23:173-196. P a r m e n t e r , L. 1944. B e h a v i o u r o f S y r i t t a p i p e n s L. ( D i p t e r a , S y r p h i d a e ) . E n t . mon. Mag. 80:44. I_n M a i e r , C.T., and G.P. W a l d b a u e r . 1979. i b i d . Pechuman, L . L . 1967. O b s e r v a t i o n s on t h e b e h a v i o r of t h e bee A n t h i d i u m manicatum L. J . N.Y. e n t . Soc. 75:68-73. P r o k o p y , R . J . , and G.L. Bush. 1972. M a t i n g b e h a v i o u r i n R h a g o l e t i s p o m o n e l l a ( D i p t e r a : T e p h r i t i d a e ) . I I I . Male a g g r e g a t i o n i n r e s p o n s e t o an a r r e s t a n t . Can. E n t . 104: 275-283. P r o k o p y , R . J . , and G.L. Bush. 1973. M a t i n g b e h a v i o u r of R h a g o l e t i s p o m o n e l l a ( D i p t e r a : T e p h r i t i d a e ) . IV. C o u r t s h i p . Can. E n t . 105:873-891. P y l e , R.M. 1972. L i n i e n i t i s l o r q u i n i ( N y m p h a l i d a e ) a t t a c k i n g a g l a c o u s - w i n g e d g u l l . J . l e p i d . S o c. 26:261. 1 28 Raw, A. 1975a. The b e h a v i o u r of males of t h e s o l i t a r y bee Osmia  r u f a s e a r c h i n g f o r f e m a l e s . Behav; 56;279-285. Raw, A. 1975b. T e r r i t o r i a l i t y and s c e n t m a r k i n g by C e n t r i s m a l e s (Hymenoptera, A n t h o p h o r i d a e ) i n J a m a i c a . Behav. 54: 311-321. R i c h a r d s , A.M. 1980. S e x u a l s e l e c t i o n , g u a r d i n g and s e x u a l c o n f l i c t i n a s p e c i e s o f C o c c i n e l l i d a e ( C o l e o p t e r a ) . J . A u s t . e n t . S o c . 19:26. R i c h a r d s , L . J . 1982 i n p r e s s . S e x - r e l a t e d f o r a g i n g d i f f e r e n c e s i n an i n t e r t i d a l b e e t l e . R o l l o , C D . 1978. P e r s . comm. r e : G e r r i s . McMaster U n i v e r s i t y , H a m i l t o n , O n t a r i o , Canada. Schone, H., and J . Tengo. 1981. C o m p e t i t i o n o f males., c o u r t s h i p b e h a v i o u r and c h e m i c a l c o m m u n i c a t i o n i n t h e d i g g e r wasp Bembix r o s t r a t a (Hymenoptera, S p h e c i d a e ) . Behav. 77:44-66. S c h o w a l t e r , T.D., and W.G. W h i t f o r d . 1979. T e r r i t o r i a l b e h a v i o u r of B o o t e t t i x a r g e n t a t u s B r u n e r ( O r t h o p t e r a : A c r i d i d a e ) . Am. m i d l . N a t . 102:182-184. S c o t t , J.A. 1974. M a t e - l o c a t i n g b e h a v i o r of b u t t e r f l i e s . Am. m i d l . N a t . 91:103-117. S e v e r i n g h a u s , L . L . , B.H. R u r t a k , and G.C. E i c k w o r t . 1981. The r e p r o d u c t i v e b e h a v i o r of A n t h i d i u m manicatum (Hymenoptera: M e g a c h i l i d a e ) and t h e s i g n i f i c a n c e o f s i z e f o r t e r r i t o r i a l m a l e s . Behav. E c o l . S o c i o b i o l . 9:51-58. S i l b e r g l i e d , R.E. 1979. Communication i n t h e u l t r a v i o l e t . Ann. Rev. E c o l . S y s t . j_0:373-398. S i n g e r , M . C , and P. Wedlake. 1981. C a p t u r e does a f f e c t p r o b a b i l i t y of r e c a p t u r e i n a b u t t e r f l y s p e c i e s . E c o l . E n t . 6:215-216. 1 29 S m i t h , D . C , and R.J. P r o k o p y . 1980. M a t i n g b e h a v i o u r of R h a g o l e t i s p o m o n e l l a ( D i p t e r a : T e p h r i t i d a e ) . V I . . S i t e • o f e a r l y s e a s o n e n c o u n t e r s . Can. E n t . 112:585-590. . South.wood, T.R.E. 1962. M i g r a t i o n o f t e r r e s t r i a l a r t h r o p o d s i n r e l a t i o n t o h a b i t a t . B i o l . Rev. 37:171-214. S p i e t h , H.T. 1968. E v o l u t i o n a r y i m p l i c a t i o n s of s e x u a l b e h a v i o r i n D r o s o p h i l a . E v o l . B i o l . 2:157-193. von F r i s c h , K. 1971. Bees: T h e i r V i s i o n , C h e m i c a l S e n s e s and Language. Rev. Ed. C o r n e l l U n i v . P r e s s , I t h a c a . 157pp. W a i n w r i g h t , C M . 1978. Hymenopteran t e r r i t o r i a l i t y and i t s i n f l u e n c e s on t h e p o l l i n a t i o n e c o l o g y of L u p i n u s a r i z o n i c u s . S o u t h w e s t . N a t . 23:605-616. W e l l i n g t o n , W.G. 1953. Motor r e s p o n s e s e v o k e d by t h e d o r s a l o c e l l i of S a r c o p h a q a a l d r i c h i P a r k e r , and t h e o r i e n t a t i o n of t h e f l y t o p l a n e p o l a r i z e d l i g h t . N a t u r e 172:1177. W e l l i n g t o n , W.G. 1964. Q u a l i t a t i v e c h a n g e s i n p o p u l a t i o n s i n u n s t a b l e e n v i r o n m e n t s . Can. E n t . 96:436-451. W e l l i n g t o n , W.G. 1974a. A s p e c i a l l i g h t t o s t e e r by. N a t . H i s t . 83:46-53. W e l l i n g t o n , W.G. 1974b. Bumblebee o c e l l i and n a v i g a t i o n a t du s k . S c i e n c e 183:550-551. W e l l i n g t o n , W.G. 1976. A p p l y i n g b e h a v i o r a l s t u d i e s t o e n t o m o l o g i c a l p r o b l e m s , pp. 87-97 ijn J . A n d e r s o n and H. Kaya ( E d s . ) , P e r s p e c t i v e s i n F o r e s t E n t o m o l o g y . Academic P r e s s , New Y o r k . W e l l i n g t o n , W.C, and D. C m i r a l o v a . 1979. Com m u n i c a t i o n of h e i g h t by f o r a g i n g h o n e y b e e s , A p i s m e l l i f e r a l i g u i s t i c a (Hymenoptera, A p i d a e ) . Ann. e n t . Soc. Am. 72:167-170. 130 W i l c o x , R.S. 1979. Sex d i s c r i m i n a t i o n i n G e r r i s r e m i q i s : r o l e of a s u r f a c e wave s i g n a l . S c i e n c e 206:1325-1327. W i l l i a m s o n , E.B. 1899. The d r a g o n f l i e s o f I n d i a n a . I n d . D e p t . g e o l . n a t . Res., 2 4 t h Ann. Rep. pp. 299-333. I_n J a c o b s , M.E. 1955. i b i d . W i l s o n , E.O. 1971. The I n s e c t S o c i e t i e s . B e l k n a p P r e s s o f H a r v a r d U n i v . P r e s s , C a m b r i d g e , Mass. 548 pp. W i l s o n , E.O. 1975. S o c i o b i o l o g y : The New S y n t h e s i s . B e l k n a p P r e s s of H a r v a r d U n i v . P r e s s , C a m b r i d g e , Mass.. 697 pp. W i l s o n , F. 1961. A d u l t r e p r o d u c t i v e b e h a v i o u r i n A s o e c u s b a s a l i s (Hymenoptera: S c e l i o n i d a e ) . A u s t . J . Z o o l . 9:739-751. W o o d v i l l e , H.C. 1970. N a r c i s s u s f l i e s , pp. 6-13 i_n N a r c i s s u s P e s t s . G.B. M i n . A g r i c . F i s h , and Food, B u l l . 51. Wynne-Edwards, V.C. 1962. A n i m a l D i s p e r s i o n i n R e l a t i o n t o S o c i a l B e h a v i o u r . O l i v e r and Boyd, E d i n b u r g h . 653 pp. APPENDIX I DATE LOCAL APPARENT (SUN) TIME 1100 1130 1200 1230 1300 A p r i l 21 50 — 53 — 50 May 21 57 60 61 60 57 J u n e 21 61 64 64 .3 64 61 J u l y 21 57 60 61 60 57 A u g u s t 21 50 — 53 • — 50 September 21 39 41 • — 39 A p p r o x i m a t e maximum s o l a r e l e v a t i o n , i n d e g r e e s , a t V a n c o u v e r , Canada (49 16' N l a t . ) . P o l a r i z e d l i g h t d i s a p p e a r s f r o m t h e z e n i t h when t h e s o l a r a n g l e i s g r e a t e r t h a n o r e q u a l t o 60 ( u n l e s s t h e s k y i s e x c e s s i v e l y t u r b i d , i n w h i c h c a s e t h i s r e l a t i o n s h i p v a r i e s s l i g h t l y ) . APPENDIX II BEHAVIOURAL DATA The frequency d i s t r i b u t i o n s presented here are constructed from the output of the "streak" program (described i n Materials and Methods). A l l behavioural sequences graphed consist of three behaviours. In s i x of the nine histograms, the sum of the number of observations i n each column does not t o t a l "n", because there were too many sequences which occurred only once or twice to graph them a l l . The following symbols are used: w P g watch hover m h i goaway mate hover cc c inspect chase chase-contact nb nf ng fb f f fg nbask nf eed ngroom f bask f f eed fgroom 133 A. MERODON EQUESTRIS 140-n = 6 0 l 120-100-f-CO W o w c/ w CO o PS w 8 0 6 0 40-2 0 -0 p w c nb cc ng g nf m i f b f f fg SEQUENCES ENDING IN A l . D i s t r i b u t i o n of the t o t a l number of behavioural sequences. 134 A. MERODQN EQUESTRIS 3 2 . 3 0 2 5 4 204-15 4-1 0 0 r-nb-cc-wn w -cc -w n b - c - w w - c - w n = 117 W - P - W MOST FREQUENT SEQUENCES ENDING IN 'w' A 2 . D i s t r i b u t i o n of the most frequent sequences ending i n 'watch'. 135 A. MERODON EQUESTRIS 5 0 4 5 4 0 -3 5 -3 0 -2 5 00 w u Z w o* w oo O 3 2 0 15 + 10+ n= 132 c - n b - p c c - w - p c - w - p _n b-cc-p_ w-cc -p w - c - p MOST FREQUENT SEQUENCES ENDING IN 'p' A3. D i s t r i b u t i o n of the most frequent sequences ending i n ' p a t r o l ' . 136 B. EUMERUS TUBERCULATUS 10 CO w o 25 W W CO fa o cr; w •3 3 1 0 0 " 9 0 -80 -• 70 60 t 50" 4 0 3 0 2 0 10 0 n = 3 2 8 w i s nb ng fb g fg SEQUENCES ENDING IN B l . D i s t r i b u t i o n of the t o t a l number of behavioural sequences. Note the absence of 'chase-contact'. 137 B. EUMERUS TUBERCULATUS 35-3 0 4 25 2 0 15 0 n = 7 0 MOST FREQUENT SEQUENCES ENDING IN 'p' B2. D i s t r i b u t i o n of the most frequent sequences ending i n ' p a t r o l ' 138 B. EUMERUS TUBERCULATUS co w CJ w o-w co Pn o erf W 5 0 45 I 5 10 5 0 n = 110 nb-p—w nb—c—w w— p —w w— e —w ---MOST FREQUENT SEQUENCES ENDING IN 'w' B3 • Distribution of the most frequent sequences ending in 'watch'. 139 C. ERISTALIS TENAX 125 120 no 100 9 0 8 0 f 7 0 co w o is w cy w CO Pu O g 6 0 5 0 ' 4 0 3 0 2 0 10 0 n = 4 2 nb w i ng h SEQUENCES ENDING IN c c C l . D i s t r i b u t i o n of t o t a l number of behavioural sequences. Note that ' p a t r o l ' i s rare, 'hover' i s present, and 'inspect' occurs more frequently than i n the other two species. 140 C. ERISTALIS TENAX 25 n = 148 201 w-c-nb CO w CJ S3 W c w CO o w n b-c-nb w-cc-w nb-c-w * 104-w-c-w hb-i-n b w—i —w MOST FREQUENT SEQUENCES ENDING IN 'w' AND 'nb' C2. D i s t r i b u t i o n of the most frequent sequences ending i n 'watch' and 'nbask'. 141 C. ERISTALIS TENAX 25T n » 122 2 0 1 CO w c_> ts Pd & o* w co Pu O erf W 15 I 0 1 0 Icc-n b-c c-nb-c cc-w-c c—w-c MOST FREQUENT SEQUENCES ENDING.IN 'c' C3. D i s t r i b u t i o n of the most frequent sequences ending i n 'chase'. 

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