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Maternal influences on size in the Cinnabar moth Richards, Laura Jean 1978

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MATERNAL INFLUENCES ON SIZE IN THE CINNABAR MOTH BY LAURA JEAN RICHARDS B.Sc. , Dalhousie . U n i v e r s i t y , 1976 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOB THE DEGREE OF THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We ac c e p t the t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLOMBIA December, 1978 MASTER OF SCIENCE Laura Jean Richards, 1978 In presenting th i s thes i s in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that I further agree that permission for extensive copying of th i s thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of th is thes i s for f inanc ia l gain sha l l not be allowed without my written permission. the L ibrary shal l make it f ree ly ava i l ab le for reference and study. Department of The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1WS Date c(kc^ AB STB ACT G e n e t i c a n d n o n - g e n e t i c e f f e c t s o f m a t e r n a l ; s i z e w e r e i n v e s t i g a t e d i n f o u r i n t r o d u c e d p o p u l a t i o n s o f C i n n a b a r m o t h T y r i a j a c o b a e a e ( L . } ( A r c t i i d a e ) . o f f s p r i n g o f d i f f e r e n t f e m a l e m o t h s w e r e r e a r e d t o t h e p u p a l s t a g e u n d e r g r e e n h o u s e c o n d i t i o n s w i t h a n o v e r a b u n d a n c e o f f o o d . Mean o f f s p r i n g -m a t e r n a l s i z e c o r r e l a t i o n s w e r e h i g h e s t f o r s e c o n d g e n e r a t i o n l a b o r a t o r y o f f s p r i n g u s i n g p u p a l w e i g h t a s t h e s i z e c r i t e r i o n , mazimum e g g w e i g h t was n o t r e l a t e d t o f e m a l e s i z e , a l t h o u g h a v e r a g e e g g w e i g h t t e n d e d t o d e c r e a s e , a n d f e c u n d i t y i n c r e a s e w i t h f e m a l e w i n g l e n g t h . E g g w e i g h t was n o t r e l a t e d t o f i n a l p u p a l w e i g h t . I g g w e i g h t d e c r e a s e d o v e r t h e o v i p o s i t i o n p e r i o d , b u t p u p a e r e a r e d f r o m l a t e r b a t c h e s a e r e n o t c o n s i s t e n t l y c f l o w e r w e i g h t when c o m p a r e d w i t h p u p a e r e a r e d f r o m b a t c h e s l a i d o n t i e f i r s t d a y o f o v i p o s i t i o n . U n d e r a l e s s f a v o r a b l e t e m p e r a t u r e r e g i m e , h a t c h i n g , s u c c e s s was r e d u c e d i n l a t e r b a t c h e s . I t was c o n c l u d e d t h a t m a t e r n a l e f f e c t s ( g e n e t i c a n d n o n - g e n e t i c ) on o f f s p r i n g s i z e a r e u n i m p o r t a n t u n d e r n o r m a l f i e l d c o n d i t i o n s i n c o m p a r i s o n t o t h e e f f e c t s e x e r t e d by l a r v a l c r o w d i n g a n d f o o d a v a i l a b i l i t y . H o w e v e r u n d e r v e r y p o o r c o n d i t i o n s , s e l e c t i v e m o r t a l i t y may be i m p o s e d on l a t e r b a t c h e s , o r on t h e l i g h t e r e g g s o f l a r g e m o t h s . 11 T A B L E OF CONTENTS A JB ST R ACT m m m m n * • m m o * m m • * m m mm .m o «• « * : o * *» • * m .' XX Xi I ST 0-1? T A H-Li ES <•<»** • • « :. i v ST OJ? - F.XG U R ES •« «.••«» * * o . • •.«»•.•'..... V ACKNOWLE DGEMENTS » • • » : VX XSTfiOiDDCTJL0N • • • *>••;•••,• • • • . 1 ^ MATERIALS AND METHODS . . . . . . . . . . . . . . . . v . . . . . - , r * . - . - . , - . - 5 f i e l d C o l l e c t i o n s .« . . . .• . .« . . .>• . . . . .» . . . . . . ' . . » .• .•<»•. .•»«•••<». 5 H e a r i n g T e c h n i g u e s : P u p a e . . . . . . . . . . . . . . . . . . r . 8 , B e a r i n g T e c f a n i g u e s : H a t i n g And Egg C o l l e c t i o n . . . . . . . . . 8 P u p a l W e i g h t E x p e r i m e n t . . .«•.* , -*.,.-.•,.=<,•>..,.--,. 3 Egg H e i g h t ' E x p e r i m e n t . . . . . . . . . . . . . . . . . • . , • > • - a - » • - • .r ! ; T3 H 3k t c i i x fi £j S u c c e s s * m m m «••.••«• • • • • • • • »^ *^  • , "1 M R ES 13 I*T S m m-m <a • « <•« * « • * <* «• • m <m m mm. * • * - ^ ^ P u p a l H e i g h t E x p e r i m e n t . . . . . . . . . . v . . . Egg W e i g h t E x p e r i m e n t - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Ha t c h i n g S u c c e s s ^ . . . . . . m . . . . « . . . . ;. 3 2 O f f s p r i n g Egg And P u p a l W e i g h t . . . . . . . . . . . . . . . . . . . , . ; .37-D X.SO OSS 10 H m m * mm, m m m m my m <• f m m m-.mmm,m_mm • m m m m m m m m: m w. • * «• « » m m.m- 4 ^ JL XT EH AT II HE OX TED * -» * * * *.*•*/<•« « .. ^ 9 i v LIST OF TABLES Table I : Source Of Families For Pupal Height Table II : Offspring-ffiaternal Size Correlations-, .»,»,- 16 Table I I I ; Size Correlations P a r t i a l l e d On Family Size. ? 1 • m .m mm.» m. -m <m-.m m m, m m -m m m m-» -m m -m * • • a « • • • a :a • • * • . « . « a • a mm- •'*».; * m m \ m m *? Table IV : Hatching Success At 15° C. -.-.-.»«.....»-.-, 35 Table V : Pupal Heights For F i r s t And Later Batches- --39 LIST OF FIGUSES Figure 1 : Offspring-parent Regressions For Body Size- 18 Figure 2 : Mean Egg Weight By Oviposition Day. 26 Figure 3 i Egg Batch Size By Oviposition Day.,, 29 Figure 4 : Hatching Success By Oviposition Day- 33 ACKNOWLEGDEMENTS T h e r e a r e a n u m b e r o f p e o p l e t o whom I w i s h t o e x p r e s s my t h a n k s . R o s m a r i e I y e r t a u g h t me t h e b a s i c h a n d l i n g t e c h n i q u e s f o r C i n n a b a r m o t h . S a n d y O c k e n d e n a n d C a t h y R e d s e l l w e r e o f i n v a l u a b l e a s s i s t e n c e b o t h i n t h e l a b a n d i n t h e f i e l d . M r s . S . G o s s a r d k i n d l y p r o v i d e d a c c o m m o d a t i o n i n C a l i f o r n i a , a n d D r . P . M c E v o y i n O r e g o n . D r s . E . N e i l l a n d J . D . M c P h a i l made h e l p f u l s u g g e s t i o n s a t v a r i o u s s t a g e s o f t h i s w o r k . F i n a l l y , my s u p e r v i s o r D r . J u d y M y e r s d e s e r v e s s p e c i a l c r e d i t f o r h e r c o n t i n u a l s u p p o r t a n d e n c o u r a g e m e n t . , She c o l l e c t e d t h e p u p a e f r o m F o r t B r a g g a n d t h e a d u l t m o t h s f r o m Nova S c o t i a f o r t h e 1977 e x p e r i m e n t s . 1 INTRODUCTION B o d y s i z e i n i n s e c t p o p u l a t i o n s i s r e m a r k a b l y v a r i a b l e b o t h b e t w e e n a n d w i t h i n s p e c i e s i n d i f f e r e n t g e o g r a p h i c r e g i o n s ( S c h o e n e r a n d J a n z e n 1 9 6 8 , B r y a n t 1977) a n d w i t h i n s p e c i e s o v e r s e a s o n a l c y c l e s ( B r y a n t 1 9 7 7 , D a n t h a n a r a y a n a 1 9 7 6 ) . N u m e r o u s f a c t o r s h a v e b e e n i m p l i c a t e d a s c a u s a l a g e n t s o f t h i s v a r i a t i o n , i n c l u d i n g c l i m a t e ( D a n t h a n a r a y a n a 1 9 7 6 ) , t e m p e r a t u r e (Sweeney and V a n n o t e 1 9 7 8 ) , d e n s i t y ( K l o m p 1 9 6 6 , G r u y s 197.1).,. a n d f o o d a b u n d a n c e a n d q u a l i t y ( v a n d e r M e i j d e n 1 9 7 6 , R o s e 1 9 7 8 ) . B e c a u s e f e c u n d i t y i s d i r e c t l y r e l a t e d t o b o d y s i z e i n many a n i m a l s , i n c l u d i n g i n s e c t s ( K l o m p 1 9 6 6 , S h i g a 1 9 7 7 ) , a n d b e c a u s e d i s p e r s a l b e h a v i o u r i s a f f e c t e d by b o d y s i z e i n some i n s e c t s ( R o s e 1 9 7 2 , S a n d e r s a n d L u c u i k 1 9 7 5 , S h i g a 1 9 7 7 ) / b o d y s i z e i s a n e c e s s a r y c o m p o n e n t t o m o d e l s o f p o p u l a t i o n d i s t r i b u t i o n and a b u n d a n c e . Hhen p o p u l a t i o n s a r e f o l l o w e d o v e r s e v e r a l g e n e r a t i o n s , m a t e r n a l i n f l u e n c e s on b o d y s i z e mus t a l s o be c o n s i d e r e d . The m a g n i t u d e o f t h i s e f f e c t w i l l d e t e r m i n e how q u i c k l y p o p u l a t i o n s 2 c a n r e s p o n d t o e n v i r o n m e n t a l c h a n g e s , t h a t i s , how q u i c k l y p o p u l a t i o n s c a n t r a c k t h e i r i m m e d i a t e e n v i r o n m e n t , a n d w h e t h e r s u c h t r a c k i n g r e g u i r e s g e n e t i c c h a n g e i n t h e p o p u l a t i o n -M a t e r n a l s i z e e f f e c t s h a v e b e e n r e c o g n i z e d u n d e r f i e l d c o n d i t i o n s i n o n l y a f ew c a s e s . B a r b o s a a n d C a p i n e r a (MS) i n t h e i r w o r k on g y p s y moth L y m a n t r i a d i s p a r , f o u n d f e m a l e s w h i c h d e v e l o p e d f r o m l a r g e e g g s p r o d u c e d more l a r g e e g g s t h a n d i d f e m a l e s w h i c h d e v e l o p e d f r o m s m a l l e g g s . T h i s r e s u l t i n d i c a t e d t h a t e g g s i z e was t o some e x t e n t i n h e r i t e d . E g g s i z e d i f f e r e n c e s were l a t e r r e f l e c t e d i n l a r v a l d i s p e r s a l b e h a v i o u r . L a r g e l a r v a e f r o m l a r g e e g g s were more a c t i v e d i s p e r s e r s t h a n s m a l l l a r v a e f r o m s m a l l e g g s ( C a p i n e r a a n d B a r b o s a 1 9 7 6 ) . P o p u l a t i o n s o f c i n n a b a r m o t h ( T y r i a j a c o b a e a e ( L . ) : A r c t i i d a e ) i n E n g l a n d u n d e r g o p e r i o d i c f l u c t u a t i o n s a s s o c i a t e d w i t h o v e r c r o w d i n g a n d s t a r v a t i o n . A s a r e s u l t , b o d y s i z e i s h i g h l y v a r i a b l e f r o m cne y e a r t o t h e n e x t ( D e m p s t e r 1 9 7 1 ) . I n N o r t h A m e r i c a , some C i n n a b a r p o p u l a t i o n s e x h i b i t s i m i l a r 3 o v e r c r o w d i n g a n d v a r i a t i o n i n body s i z e ( M y e r s 1 9 7 8 ) , b u t i n o t h e r s , p o p u l a t i o n f l u c t u a t i o n s a r e r e d u c e d ( N a g e l a n d I s a a c s o n 1 9 7 4 , M y e r s a n d C a m p b e l l 1 9 7 6 . ) . M y e r s (1978) h a s s u g g e s t e d t h a t an a b i l i t y t o p u p a t e a t a s m a l l s i z e i s one o f t h e f a c t o r s l e a d i n g t o s t a b i l i z a t i o n o f d e n s i t i e s i n t h e s e p o p u l a t i o n s . , F r o m l a b o r a t o r y s t u d i e s i t h a s b e e n d e t e r m i n e d t h a t c r o w d i n g , f o o d s h o r t a g e a n d p o o r f o o d q u a l i t y ( l o w n u t r i e n t l e v e l s a n d a l a c k o f i n f l o r e s c e n c e s i n t h e d i e t ) , l e a d t o a r e d u c t i o n i n p u p a l s i z e ( D e m p s t e r 1 9 7 1 , v a n d e r M e i j d e n 1 9 7 6 , R o s e 1 9 7 8 , B - P o s t p e r s . c o m . ) . H e r e I t e s t t h e h y p o t h e s i s t h a t m a t e r n a l s i z e i s a l s o an i m p o r t a n t i n f l u e n c e on e g g a n d p u p a l s i z e . A s s u m i n g t h a t a l a r g e m a t e r n a l c o m p o n e n t t o s i z e i s p r e s e n t , a n d t h a t g e n e t i c a l l y l a r g e l a r v a e r e g u i r e more f o o d p r i o r t o p u p a t i o n t h a n g e n e t i c a l l y s m a l l l a r v a e , f o o d s h o r t a g e s w i l l s e l e c t a g a i n s t l a r g e s i z e . S u c h s e l e c t i o n i s b a l a n c e d a g a i n s t t h e a d v a n t a g e i n h i g h f e c u n d i t y o f l a r g e s i z e when t h e s e p r e s s u r e s a r e r e d u c e d . 4 LIFE HISTORY Adult Cinnabar moths are found i n the f i e l d between May and July- Females mate soon a f t e r emergence and lay t h e i r eggs i n batches averaging 30 to 50 eggs on the underside of leaves of tansy ragwort, Senecio jacobaea L.. The egg stage l a s t s a week, and another month i s required f o r completion of the f i v e l a r v a l instars- Bhen f i n a l s i z e i s reached and feeding ceases, larvae disperse i n search of dark and enclosed s i t e s i n which to pupate and overwinter- Further d e t a i l s may be found i n Dempster (1971) and Green (1974)-M A T E R I A L S AND METHODS F I E L D C O L L E C T I O N S P u p a e o r a d u l t f e m a l e s u s e d i n t h i s s t u d y w e r e c o l l e c t e d f r o m f o u r C i n n a b a r p o p u l a t i o n s ; F o r t B r a g g , S i l b e r n a g e l , C u l t u s L a k e a n d N o v a S c o t i a { T a b l e I ) . S i t e d e s c r i p t i o n s a n d a h i s t o r y o f t h e i n t r o d u c t i o n o f C i n n a b a r moth t o t h e s e a r e a s may be f o u n d i n C a m p b e l l (1975) a n d M y e r s and C a m p b e l l ( 1 9 7 6 ) . F i e l d - c o l l e c t e d f e m a l e s were u s e d when p u p a e c o u l d n o t b e o b t a i n e d o r when p o o r e m e r g e n c e o r m a t i n g s u c c e s s n e c e s s i t a t e d a n i n c r e a s e i n s a m p l e s i z e . C u l t u s L a k e p u p a e r e a r e d f r o m l a r v a e i n 1977 were u s e d f o r e g g w e i g h t , h a t c h i n g s u c c e s s a n d some o f t h e p u p a l w e i g h t e x p e r i m e n t s i n 1 9 7 8 . 6 T a b l e I z S o u r c e o f f a m i l i e s f o r p u p a l w e i g h t e x p e r i m e n t s . C o l l e c t i o n d a t e s , t h e l i f e - h i s t o r y s t a g e c o l l e c t e d , a n d t h e n u m b e r o f f a m i l i e s r e a r e d i n p u p a l w e i g h t e x p e r i m e n t s f r o m t h a t c o l l e c t i o n a r e s h o w n f o r e a c h p o p u l a t i o n -1 7 POPULATION N STAGE COLLECTION DATE Fort Bragg Mendicino Co. Cal i fornia Silbernagel Linn Co. Oregon Cultus Lake Br i t i sh Columbia 3 11 5 18 2 14 8 8 9 pupal adult pupal adult pupal adult adult pupal adult Jan. 1977 June 1977 Jan. 1977 May 1978 Feb. 1977 June 1977 July 1977 lab-reared 1977 June 1978 Nova Scotia 11 adult July 1977 8 fiEASING T E C H N I C P E S : P U P A E P u p a e f o r 1977 e x p e r i m e n t s w e r e s e x e d a n d w e i g h e d o n a S e t t l e r H20 T b a l a n c e p r i o r t o e m e r g e n c e i n A p r i l a n d May 1 9 7 7 . P u p a e f o r 197 8 e x p e r i m e n t s w e r e s e x e d a n d w e i g h e d b e t w e e n S e p t e m b e r a n d N o v e m b e r 1 9 7 7 , d i v i d e d i n t o 5mg w e i g h t c l a s s e s , a n d a s s i g n e d t h e w e i g h t a t t h e l o w e r b o u n d a r y o f t h e c l a s s -H e i g h t c l a s s e s r a n g e d f r o m 1 4 0 - 1 4 5 m g t o 2 4 0 - 2 4 5 m g . R E A R I N G T E C H N I Q U E S : MATING AND EGG C O L L E C T I O N P a i r s w e r e p l a c e d i n p a p e r m i l k s h a k e c o n t a i n e r s (11cm d i a m e t e r , 15cm deep ) c o v e r e d w i t h a s q u a r e o f c h e e s e c l o t h . A t a n s y r a g w o r t l e a f i n a s m a l l v i a l o f w a t e r was p r o v i d e d f o r e g g l a y i n g . C o n t a i n e r s w e r e c h e c k e d a n d a l l e g g s r e m o v e d d a i l y . The m a l e was r e m o v e d a s s o o n a s t h e f i r s t b a t c h was l a i d . I f no e g g s h a d a p p e a r e d by t h e f o u r t h o r f i f t h d a y , t h e m a l e was e x c h a n g e d . M o t h s f o r w h i c h m a t e s w e r e u n a v a i l a b l e 9 were s t o r e d a t 1 5 ° C . Such s t o r a g e , i f on ly f o r a few d a y s , d i d not appear to a f f e c t l a t e r per formance . F i e l d - c o l l e c t e d females were assumed to have mated, but were o t h e r w i s e t r e a t e d i d e n t i c a l l y to lab-emerged f e m a l e s . , As age o f these females was unknown, the f i r s t egg b a t c h l a i d i n the l a b o r a t o r y was no t n e c e s s a r i l y the f i r s t l a i d by t h a t f emale . L e n g t h o f the forewing e x c l u d i n g the wing c i l i a was measured to the n e a r e s t 0.01cm with v e r n i e r c a l i p e r s as soon as p o s s i b l e a f t e r c o l l e c t i o n of the moths. PUPAL HEIGHT EXPERIMENT F i r s t i n s t a r l a r v a e were t r a n s f e r r e d from the l e a f on which the eggs were l a i d to p o t t e d ragwort p l a n t s l o c a t e d i n a greenhouse . Care was taken to ensure s e p a r a t i o n of o f f s p r i n g from d i f f e r e n t female moths. T h i s was p o s s i b l e by keeping t h e 10 p l a n t s i n c a r d b o a r d b o x e s w h i c h w e r e t r e a t e d w i t h S t i c k u m o n t h e e d g e s . R e p e a t e d o b s e r v a t i o n s c o n f i r m e d t h a t l a r v a e w i l l n o t c r o s s t h i s s t i c k y s u b s t a n c e . To m i n i m i z e p o s s i b l e e f f e c t s o f b a t c h o r d e r , l a r v a e w e r e u s e d o n l y f r o m e g g s l a i d on t h e f i r s t d a y o f o v i p o s i t i o n , o r i n t h e c a s e o f f i e l d - c o l l e c t e d f e m a l e s , f r o m t h e f i r s t b a t c h l a i d i n t h e l a b o r a t o r y . Numbers w e r e k e p t a t a maximum o f a b o u t 20 p e r p l a n t ( b o x e s h e l d one t o t h r e e p l a n t s ) . Any i n e x c e s s were a r b i t r a r i l y k i l l e d , b u t o t h e r w i s e no c o n t r o l s o n d e n s i t y were m a i n t a i n e d . P l a n t s w e r e r e p l a c e d w h e n e v e r t h e y s h o w e d s i g n s o f d e f o l i a t i o n . T h i s meant t h a t e a c h f a m i l y h a d an o p p o r t u n i t y t o f e e d o n a b o u t f o u r t o e i g h t d i f f e r e n t r a g w o r t p l a n t s b e f o r e p u p a t i o n . As s o o n a s t h e f i r s t few f i f t h i n s t a r l a r v a e h a d b e g u n t o c r a w l a c t i v e l y i n s e a r c h o f a p u p a t i o n s i t e a n d r e f u s e d f u r t h e r f o o d , a l l l a r v a e i n t h a t f a m i l y w e r e t r a n s f e r r e d t o m i l k s h a k e c o n t a i n e r s . C u t l e a v e s a n d i n f l o r e s c e n c e s f r o m r a g w o r t p l a n t s , k e p t f r e s h i n a j a r o f w a t e r u n d e r t h e c o n t a i n e r , w e r e 11 provided as a d d i t i o n a l food. Containers sere cleaned daily and food replaced as required. Pupae were stored i n covered p e f r i dishes for approximately two months prior to being weighed and sexed. About 25% of the pupae i n 1977 were malformed and had to be discarded, possibly due to high temperatures i n the greenhouse (Philogeae 1975) or disturbance at the time of pupation. This necessitated a few changes i n rearing techniques i n 1978. Tight controls were also placed on density to prevent family size from confounding the r e s u l t s . Fifteen f i r s t i nstar larvae were a r b i t r a r i l y selected from the f i r s t batch l a i d by each female, and divided between two ragwort plants i n a cardboard box. Plants were replaced as required from a stock supply. Only f i f t h i n s t a r larvae which were a c t i v e l y crawling and which refused food were removed from plants and placed into containers f o r pupation. These containers did not contain food. Pupation s i t e s were provided by 3cm lengths of p l a s t i c drinking straws (suggested by Rose 12 (1978)) and crinkled s t r i p s of paper towelling.. Containers were l e f t undisturbed f o r 10 to 14 days- Pupae were then removed, sexed, and weighed- This change of procedure reduced mortality from f i r s t i n s t a r to pupa to i n s i g n i f i c a n t l e v e l s . Offspring-mother co r r e l a t i o n s were performed on the family means of the offspring of each sex using wing length and pupal weight ( i f known) f o r the maternal measurements. , Each family was given an egual weight in the analysis, unless the family mean was based on one pupa only, i n which case i t was excluded. For 1977 experiments, when density, controls were not maintained, the t o t a l number surviving u n t i l the time of measurement varied from 0 to 74 pupae f o r one family. As females are heavier than males, sexes were treated separately i n the analysis. 13 EGG WEIGHT EXPERIMENT A l l batches of 5 or more eggs l a i d by each female were collected- Eggs were dried at 65° C for one to two days and stored i n a desiccator prior to being weighed on a Cahn G-2 Electrobalance. To act as a check on measurement error, batches were weighed by dividing the eggs into several groups, with at least fi v e eggs i n each group. Because i t was not possible to distinguish batch order when more than one batch was l a i d within a one day period, weight measurements were averaged over the t o t a l number of eggs l a i d . This resulted i n a jnean egg weight for each female for each day on which eggs were l a i d . A mean weight was also calculated for the entire egg complement of each female. HATCHING SUCCESS Batches of .5 or more eggs were transferred to masking tape and placed i n covered p e t r i dishes at 15° C. They sere l i g h t l y sprayed with water every few days to prevent dehydration- After approximately three weeks had elapsed (a s u f f i c i e n t time for development), eggs were counted under a dissecting scope and scored as hatched or not hatched. An egg was defined as hatched i f the larva had opened the chorion. The proportion of hatched eggs (hatching success) was computed for each female for each day of oviposition- Batches were excluded, however, i n which no eggs hatched. This precaution, taken to eliminate dehydrated or s t e r i l e batches from the analysis, may have l e d to some overestimation of the true hatching success. Proportions were standardized f o r each female by obtaining the r a t i o of the proportion hatched on each day to the proportion hatched on day 1, or on day 2 i f data from day 1 were unavailable. 15 BESULTS PUPAL WEIGHT EXPERIMENT This experiment was designed to t e s t the hypothesis that offspring pupal weight i s related to maternal s i z e . The correlations I measured are l i s t e d i n Table II f o r maternal wing length and pupal weight. The only s t a t i s t i c a l l y s i g n i f i c a n t r e s u l t s are the correlations with maternal wing length f o r female o f f s p r i n g from Fort Bragg i n 1977 and with maternal pupal weight for male and female offspring from Cultus Lake i n 1978- These data and the corresponding regression l i n e s are i l l u s t r a t e d i n Figure 1. Correlations were higher f o r females i n a l l but one case. The data presented i n Table II are complicated by the lack of control on within-family density i n 1977. To eliminate th i s potential influence I repeated the analysis using offspring-mother p a r t i a l correlations correcting for the number of pupae measured i n each family {Table I I I ) . The c o r r e l a t i o n with density was only s i g n i f i c a n t for Cultus Lake offspring, 16 Table II : Offspring-maternal size correlations-Correlations are shown between mean offspring pupal weight and maternal wing length and pupal weight-17 POPULATION MALES FEMALES n r n r maternal wing length 1977 Fort Bragg 13 0.42 11 0.68* SiLbernagel 5 -0.29 5 -0.40 Cultus Lake 22 -0.36 23 -0.19 Nova Scotia 11 0.11 11 0.43 1978 SiLbernagel 18 0.00 16 0.06 Cultus Lake 16 0.02 17 0.24 maternal pupal weight 1977 Fort Bragg 3 -0.79 4 -0.05 SiLbernagel 6 -0.78 6 -0.08 1978 Cultus Lake 8 0.80* 8 0.86** * P <0.05 ** P <0.01 g u r e 1 : o f f s p r i n g - p a r e n t r e g r e s s i o n s f o r b o d y s i z e . T h e r e l a t i o n s h i p b e t w e e n mean f e m a l e o f f s p r i n g p u p a l w e i g h t and m a t e r n a l s i z e i s shown f o r t h e F o r t B r a g g p o p u l a t i o n i n 1977 u s i n g m a t e r n a l w i n g l e n g t h ( F i g . 1a) a n d f o r t h e C u l t u s L a k e l a b p o p u l a t i o n i n 1978 u s i n g m a t e r n a l p u p a l w e i g h t ( F i g - 1b) . Figure lb 1H3I3M IVdnd 9NIcJdSJJD 21 T a b l e I I I : S i z e c o r r e l a t i o n s p a r t i a l l e d on f a m i l y s i z e -C o r r e l a t i o n s ( r ) b e t w e e n mean o f f s p r i n g p u p a l w e i g h t a n d f a m i l y s i z e a n d p a r t i a l c o r r e l a t i o n s (p) b e t w e e n mean o f f s p r i n g p u p a l w e i g h t a n d m a t e r n a l s i z e a r e s h o w n . S a m p l e s i z e s a r e a s f o r 1977 d a t a i n T a b l e I I . POPULATION MALES FEMALES r P r P maternal wing length Fort Bragg -0.14 0.46 -0, .22 0.72* Silbernagel 0.36 -0.16 -0, .47 -0.73 Cultus Lake -0.74** -0.26 -0, .66** 0.00 Nova Scotia 0.23 0.04 0, .32 0.36 maternal pupal weight Fort Bragg -0.13 Silbernagel -0.41 -0.81 -0, .37 0.00 * P< 0.05 ** P< 0.01 and i n no case did the inc l u s i o n of a density component a l t e r the s i g n i f i c a n c e of the o r i g i n a l results- However the very high correlations with Silbernagel females on maternal wing length and males on maternal pupal weight are ce r t a i n l y suggestive of a negative r e l a t i o n s h i p . The repeat of the experiment i n 1978 on two populations with a control f o r density s t i l l resulted i n non-significant offspring-maternal wing length c o r r e l a t i o n s . The possible negative correlation f o r Silbernagel disappeared with an increased sample s i z e . The eight Cultus lake f a m i l i e s for which offspring-maternal pupal weight correlations were s i g n i f i c a n t i n 1978 were the only families for which both parents were reared under greenhouse conditions. one generation i n the laboratory may have reduced environmental v a r i a t i o n i n maternal size s u f f i c i e n t l y , to make a maternal influence on offspring s i z e apparent. However, the correlations with maternal wing length f o r the same eight f a m i l i e s are non-significant (0.36 for male, 0.25 for female o f f s p r i n g ) . The c o r r e l a t i o n between female 2 4 pupal aeight and female wing length i s high (0-84, based on 1977 data for 65 females from a l l populations) but only accounts for 10% of the variation i n female wing length. The remaining 30% may have been s u f f i c i e n t to obscure c o r r e l a t i o n s which would have been found i f maternal pupal weights were known. another factor which may have affected some of the re s u l t s , i s that f o r f i e l d - c o l l e c t e d females, i t i s unlikely that the larvae reared f o r t h i s experiment were from batches l a i d on the f i r s t day of ov i p o s i t i o n . The influence of oviposition day on pupal weight i s discussed below (see section on OFFSPRING EGG AND PUPAL HEIGHTS ). In conclusion I must reject the hypothesis that o f f s p r i n g pupal weight i s related to maternal s i z e , at l e a s t under t y p i c a l f i e l d conditions. Offspring pupal weight and maternal s i z e may be related, but only when environmental determinants of s i z e are s u b s t a n t i a l l y reduced, such as i n the laboratory. S i g n i f i c a n t differences between family means did exist (tested 25 by ANOVA ) but they did not follow a l i n e a r trend with maternal s i z e , and scattergrams did not suggest non-linear trends. Some of these differences may have ref l e c t e d the common rearing environment of the offspring i n each family. EGG WEIGHT EXPERIMENT This experiment was designed to test the hypothesis that maternal e f f e c t s {primarily non-genetic) influence egg s i z e . The hypothesis was approached by measuring the mean egg weight for each day of oviposition f o r a group of females. . The pattern of decreasing egg weight with day of ovip o s i t i o n i s i l l u s t r a t e d very c l e a r l y i n Figure 2. There i s a sharp decline over the f i r s t four days. Mean egg weight i s f a i r l y constant between days 4 and 10 and increases i r r e g u l a r l y at the end of the ovip o s i t i o n period. The three females which survived to days 12 and 13 l a i d small batches (between 9 and 14 26 Figure 2 : Mean egg weight by oviposition day., Mean egg weight (+ SE) and the number of moths which l a i d egg batches are shown f o r each day of the oviposition period. 0-045 0-040 l a I—I ^ 0.035 jJ Z .< 0-030 a 4 s i A. ^ 5 5 G E T 5 0-055 0- B» 10- IE- 14 •AY Q" •VIPrj5ITIfJN 28 eggs), but these contained eggs markedly heavier than eggs l a i d over the previous several days- One female l a i d heavier eggs at t h i s time than on day 1. Along with the decrease in mean egg weight i s a decrease i n the number of eggs l a i d per batch (Fig* 3). The lar g e s t batches were l a i d on day 3, although batch s i z e over the f i r s t s i x days tended to be quite variable- Individual females l a i d up to 3 batches on any given day (more batches were l a i d early in the oviposition period) and on some days females did not lay any eggs. Figures 2 and 3 together show that more and heavier eggs are l a i d during the f i r s t few days of o v i p o s i t i o n than on l a t e r days. I obtained a weak (P<Q. 10) c o r r e l a t i o n between measurements of female si z e and the t o t a l number of eggs l a i d (c-0.62 f o r wing length, r=0.65 f o r pupal weight for 9 females). There was also a weak negative c o r r e l a t i o n between wing length and o v e r a l l mean egg weight (r= -0.58), but the results using pupal weight were not s i g n i f i c a n t (r= -0.27). g u r e 3 : E g g b a t c h s i z e by o v i p o s i t i o n d a y - Mean b a t c h s i z e (• SE) a n d t h e n u m b e r o f m o t h s w h i c h l a i d e g g b a t c h e s a r e s h o w n f o r e a c h d a y o f t h e o v i p o s i t i o n p e r i o d -120« _ B 100. S < BO- „ 3^1 1 J BO. 40. EO. 1 0. H 1- B« 10. IS* 14 •AY OF OVIPOSITION Thus small females tend to produce fewer, but heavier eggs than large females. Also I looked f o r a re l a t i o n s h i p between the maximum egg weight measurement f o r each female and female size using 19 females on which I had some data. A multiple regression of maximum egg weight on female pupal weight and female wing length was non-significant ( E 2 = 0 . 0 3 3 ) . Both the heaviest and l i g h t e s t eggs were l a i d by small females. It appears that maternal e f f e c t s acting through the order in which eggs are l a i d have a very important influence on egg weight. Female size has a s l i g h t e f f e c t , but female size differences are r e l a t i v e l y minor i n comparison to egg order differences. 32 HATCHING SPCCESS The decrease in egg weight over the oviposition period suggests that eggs i n l a t e r batches are i n some way less " f i t " than eggs in early batches- Experiments conducted f o r another study had indicated that some eggs f a i l to hatch at 15° C (Hyers pers. com.) and t h i s provided a method by which the hypothesis could be tested- Besults are i l l u s t r a t e d i n Figure 4 and are summarized by groups of oviposition days i n Table IV. There i s considerable variation among females in the proportions of eggs hatching, but when the r e s u l t s are standardized by i n i t i a l hatching success, a decreasing trend becomes apparent. Hatching success i s highest f o r the f i r s t three days of oviposition when eggs are heavy (Fig- 2) and batch si z e i s large (Fig. 3) . I t remains constant between days 4 and 9, and then drops f o r days 10 to 13. The high value for the one batch l a i d on day 12 was expected, as a few heavy eggs were produced by some females at the end of the oviposition period- In the f i e l d , i t appears that 33 F i g u r e 4 : H a t c h i n g s u c c e s s b y o v i p o s i t i o n d a y - The p r o p o r t i o n o f e g g s h a t c h i n g a t 1 5° C f o r e a c h f e m a l e moth f o r e a c h day o f t h e o v i p o s i t i o n p e r i o d i s g i v e n r e l a t i v e t o h a t c h i n g s u c c e s s on d a y 1 ( f o r e g g s f r o m 6 moths ) o r day 2 (3 moths ) when h a t c h i n g s u c c e s s on day 1 was u n k n o w n . 34 ••H <a 4 <i •2 m <1 + ID <J <1 <1 41 + <1 4 <1 .ni V n± O a lrf LD' ^ fit" o o o o o o E3NIHD1VH 3AIlVn3cJ 35 T a b l e I V z H a t c h i n g s u c c e s s a t 1 5 ° C . T h e mean a n d s t a n d a r d d e v i a t i o n ( c o m p u t e d on a r c s i n - s g u a r e r o o t t r a n s f o r m e d d a t a ) o f t h e p r o p o r t i o n s o f e g g s h a t c h i n g f o r d i f f e r e n t m o t h s f o r g r o u p s o f o v i p o s i t i o n d a y s . D a y s s e r e g r o u p e d t o b a l a n c e s a m p l e s i z e s . DAYS 1-2 3-4 5-7 8-13 n 13 8 10 9 mean 0.84 0.56 0.65 0.31 SD 0.05 0.24 0.18 0.08 unseasonably cold weather could impose a s e l e c t i v e mortality on late batches. OFFSPR ING EGG AND PUPAL H E I G H J To test the hypothesis that differences i n egg and pupal weight for batches l a i d on the f i r s t day of ovi p o s i t i o n are r e f l e c t e d i n differences i n pupal weight between f a m i l i e s , I weighed 10 eggs from most batches used for pupal weight experiments i n 1978. Correlations of egg weight and pupal weight were ncn-significant f o r both populations. Using Silbernagel as an example, the c o r r e l a t i o n for male pupae was 0.09, and -0.02 for female pupae (n=11). To test the hypothesis that differences i n egg weight within a family between batches l a i d on the f i r s t and l a t e r days of oviposition w i l l r e s u l t i n heavier pupae i n early batches, I reared larvae from two or three batches for f i v e C u l t u s L a k e f e m a l e s i n 1 9 7 8 - The d a t a a r e p r e s e n t e d i n T a b l e y . I n o n l y one o f t h e f i v e f a m i l i e s { n o t t h e same) f o r e a c h s e x was t h e mean p u p a l w e i g h t o f a l l l a t e r b a t c h e s s i g n i f i c a n t l y l o w e r . I n some c a s e s t h e mean o f t h e l a t e r b a t c h was c o n s i d e r a b l y h i g h e r . T h e v a r i a n c e s o f p u p a l w e i g h t o f l a t e r b a t c h e s were a l l e q u a l t o o r g r e a t e r t h a n t h o s e f o r e a r l y b a t c h e s . To c o n c l u d e I mus t r e j e c t b o t h h y p o t h e s e s p r e s e n t e d i n t h i s s e c t i o n . The l o w e r egg w e i g h t o f l a t e b a t c h e s d o e s n o t r e s u l t i n d e c r e a s e d p u p a l w e i g h t s , a t l e a s t u n d e r l a b o r a t o r y r e a r i n g c o n d i t i o n s . 39 T a b l e V : P u p a l w e i g h t s f o r f i r s t a n d l a t e r b a t c h e s . k c o m p a r i s o n i s g i v e n b e t w e e n mean o f f s p r i n g p u p a l w e i g h t s f o r f i v e f a m i l i e s f o r w h i c h more t h a n one b a t c h o f l a r v a e w e r e r e a r e d . S i g n i f i c a n c e l e v e l s a r e f o r a o n e - t a i l e d t - t e s t u n d e r t h e n u l l h y p o t h e s i s t h a t p u p a l w e i g h t i s l o w e r i n l a t e r b a t c h e s . V a r i a n c e s were a s s u m e d h e t e r o g e n e o u s i n c o m p u t a t i o n o f t h e t - s t a t i s t i c i f a n F -t e s t f o r h o m o g e n e i t y o f v a r i a n c e was s i g n i f i c a n t . FIRST BATCH LATER BATCHES FAMILY N MEAN SD DAY N MEAN SD male offspring 1 6 214.6 29.9 3 11 222.5 31.2 6 6 231.4 30.2 2 11 172.3 8.1 3 7 162.5* 12.1 4 3 129.3* 24.9 3 9 167.3 10.8 5 5 172.4 11.4 4 7 175.2 13.8 3 7 177.4 15.6 5 6 191.4 19.8 3 1 217.7 -female offspring 1 8 220.9 25.2 3 9 218.6 45.3 6 8 246.3 30.2 2 11 192.0 8.4 3 11 177.1 30.7 4 4 161.0** 33.9 3 8 195.3 12.4 5 9 183.3* 12.4 4 9 198.6 7.5 3 6 191.4 12.4 5 9 208.1 22.4 3 7 222.9 27.7 * P<0.05 one-tailed test ** P<0.01 one-tailed test 41 DISCUSSION Between-family differences i n mean offspring egg and pupal weight could arise i f fa m i l i e s are g e n e t i c a l l y . d i f f e r e n t , i f females d i f f e r i n resource a l l o c a t i o n to t h e i r offspring, or for pupae, i f fam i l i e s experience d i f f e r e n t rearing environments- Because of my experimental design, I cannot eliminate the p o s s i b i l i t y that a common rearing environment accounts for some of the differences observed- This has already been shown to have a large impact on pupal si z e i n the f i e l d (van der Heijden 1976)- The evidence I discuss below indicates that genetic and non-genetic maternal e f f e c t s can also influence s i z e i n f i e l d populations..,.. Klomp (1966) performed an experiment i n which he divided f i e l d - c o l l e c t e d pupae of Bupalus p i n i a r i u s into two size classes on the basis of pupal diameter- SJhen moths emerged they were mated within t h e i r size class and larvae were reared either singly or i n pairs- Hean offspring pupal diameter differed s i g n i f i c a n t l y i n the two size classes ( the larger 4 2 o f f s p r i n g f r o m t h e l a r g e r p a r e n t s ) , i n d i c a t i n g t h a t a g e n e t i c c o m p o n e n t t o p u p a l s i z e was p r e s e n t . K l o m p q u e s t i o n e d t h e s i g n i f i c a n c e o f t h e s e r e s u l t s t o f i e l d c o n d i t i o n s h o w e v e r , a s d i f f e r e n c e s b e t w e e n t h e means o f o f f s p r i n g r e a r e d s i n g l y a n d t h o s e r e a r e d i n p a i r s w e r e g r e a t e r t h a n t h e d i f f e r e n c e s b e t w e e n t h e means o f t h e o f f s p r i n g f r o m l a r g e a n d s m a l l p a r e n t s . The r e l a t i v e l y s m a l l d i f f e r e n c e s K l o m p m e a s u r e d b e t w e e n f a m i l i e s i n d i f f e r e n t s i z e c l a s s e s a n d t h e l a c k o f c o r r e l a t i o n I f o u n d i n p u p a l w e i g h t - m a t e r n a l w i n g l e n g t h c o r r e l a t i o n s a r e p r o b a b l y t o be e x p e c t e d when t h e p a r e n t a l g e n e r a t i o n d e v e l o p e d i n t h e f i e l d . B r y a n t (1977) h a s s h o w n t h a t f o r M u s c a  d o m e s t i c a , t h e u s e o f f i e l d - c a u g h t f e m a l e s r e s u l t s i n l o w e r o f f s p r i n g - p a r e n t c o r r e l a t i o n s f o r w i n g l e n g t h , t i b i a l e n g t h , a n d s c u t u m l e n g t h , t h a n when f i r s t g e n e r a t i o n l a b o r a t o r y f e m a l e s w e r e u s e d a s p a r e n t s . Why t h i s s h o u l d be c a n e a s i l y be e x p l a i n e d i n a s i m p l e v e r b a l m o d e l . The v a r i a n c e i n p u p a l s i z e c a n be c o n c e p t u a l i z e d a s h a v i n g t w o c o m p o n e n t s - a g e n e t i c c o m p o n e n t a n d a n e n v i r o n m e n t a l . 43 c o m p o n e n t . U n d e r t y p i c a l f i e l d c o n d i t i o n s , h e t e r o g e n e i t y i n f o o d a b u n d a n c e a n d l a r v a l d e n s i t y w i l l r e s u l t i n a n e n v i r o n m e n t a l c o m p o n e n t w h i c h v a r i e s g r e a t l y b e t w e e n i n d i v i d u a l s . A s a c o n s e g u e n c e , t h e o b s e r v e d p u p a l s i z e w i l l b e a r l i t t l e o r no r e l a t i o n t o i t s g e n o t y p e . G e n e t i c a l l y s m a l l p u p a e w h i c h w e r e w e l l - f e d a s l a r v a e w i l l a p p e a r h e a v i e r t h a n g e n e t i c a l l y l a r g e p u p a e w h i c h d e v e l o p e d u n d e r p o o r c o n d i t i o n s . I f r e a r i n g c o n d i t i o n s a r e r e l a t i v e l y h o m o g e n e o u s , s o t h a t t h e e n v i r o n m e n t a l c o m p o n e n t i s c o n s t a n t b e t w e e n i n d i v i d u a l s , t h e o b s e r v e d p u p a l s i z e w i l l c l o s e l y r e s e m b l e i t s g e n o t y p e . I n t h e l a b o r a t o r y , a l l l a r v a e a r e w e l l - f e d a n d s o t h e g e n e t i c c o m p o n e n t t o s i z e may b e e x p r e s s e d . * I was a b l e t o m e a s u r e a h e r i t a b l e c o m p o n e n t t o p u p a l s i z e when b o t h p a r e n t s a n d o f f s p r i n g w e r e r e a r e d i n t h e l a b o r a t o r y , b u t i n o n l y one c a s e , f o r F o r t B r a g g , when p a r e n t s w e r e f i e l d - c o l l e c t e d . The F o r t B r a g g p o p u l a t i o n i s s o m e w h a t u n u s u a l i n t h a t i t h a s m a i n t a i n e d a h i g h p o p u l a t i o n d e n s i t y f o r t h e l a s t f o u r y e a r s i n s p i t e o f s e v e r e f o o d l i m i t a t i o n i n 1976 a n d 1977 44 (Myers pers. com-). The depletion of tansy ragwort was caused not by the moth, but by introduction of a f l e a beetle Longitarsus jacobaeae as another b i o l o g i c a l c o n t r o l agent. Uniformly poor developmental conditions i n t h i s population may have resulted in a small environmental component to body s i z e variance, so that the wing lengths I measured ref l e c t e d genetic differences between ind i v i d u a l s . That i s , expression of the genetic component of the variance reguires only that conditions be homogeneous, not that they be exceptionally good as i n the laboratory. For eggs l a i d on the f i r s t day of ov i p o s i t i o n , the lack of correlations between female s i z e and maximum egg weight and between offspring pupal weight and egg weight suggest that non-genetic maternal si z e effects are minimal. Heavy females do not lay proportionately heavier eggs, and egg weight i s not a factor i n determining offspring pupal weight. There i s some evidence that both genetic and maternal e f f e c t s do become important when a i l eggs l a i d by a female are considered. B a r b o s a a n d C a p i n e r a (MS) f o u n d e g g s i z e i n L y m a n t r i a d i s p a r t o be h e r i t a b l e t o some e x t e n t . B e c a u s e I m e a s u r e d e g g s i z e f o r one g e n e r a t i o n o n l y , I w i l l r e s t r i c t my d i s c u s s i o n t o p o s s i b l e n o n - g e n e t i c m a t e r n a l e f f e c t s . V a r i a t i o n b o t h b e t w e e n a n d w i t h i n f e m a l e s f o r e g g s i z e ( w e i g h t o r d i a m e t e r ) ha s been r e p o r t e d i n B u p a l u s p i n i a r i u s ( K l o m p 1 9 6 6 ) , L y m a n t r i a d i s p a r ( L e o n a r d 1970) a n d C h o r i s t o n e u r a  f u m i f e r a n a ( H a r v e y 1 9 7 7 ) , b u t t h e r e i s no g e n e r a l a g r e e m e n t a s t o t h e r e l a t i o n s h i p b e t w e e n mean e g g s i z e and f e m a l e s i z e . , K l o m p (1966) r e p o r t e d p o s i t i v e c o r r e l a t i o n s b e t w e e n e g g d i a m e t e r a n d p u p a l d i a m e t e r f o r e a c h o f s i x y e a r s o f d a t a . He b e l i e v e d t h e r e l a t i o n s h i p t o be m e a n i n g f u l i n s p i t e o f t h e l a r g e v a r i a n c e a r o u n d h i s r e g r e s s i o n l i n e . H a r v e y (1977) f o u n d f e m a l e s f r o m h e a v i e r pupae l a i d e g g s o f s l i g h t l y l o w e r mean w e i g h t a l t h o u g h t h e d i f f e r e n c e s w e r e n o t s i g n i f i c a n t . My r e s u l t s a l s o s u g g e s t a n e g a t i v e r e l a t i o n s h i p . The o v i p o s i t i o n p a t t e r n o f C h o r i s t o n e u r a f u m i f e r a n a i s s i m i l a r t o t h a t o f C i n n a b a r m o t h . E g g s a r e l a i d i n a n u m b e r 46 o f d i s c r e t e c l u s t e r s o v e r a b o u t a t w o week p e r i o d - H a r v e y (1977) f o l l o w e d i n d i v i d u a l m o t h s a n d o b t a i n e d a d e c r e a s e i n mean e g g (wet ) w e i g h t o v e r t h e o v i p o s i t i o n p e r i o d w h i c h i s a l m o s t i d e n t i c a l t o t h e one I h a v e s h o w n i n F i g u r e 2 , i n c l u d i n g p r o d u c t i o n o f a f e w h e a v y e g g s a t t h e e n d o f t h e o v i p o s i t i o n p e r i o d b y some f e m a l e s . The mos t l i k e l y e x p l a n a t i o n i s t h e p r o g r e s s i v e d e p l e t i o n o f m a t e r i a l s r e q u i r e d f o r e g g p r o d u c t i o n . T h i s h a s a l s o b e e n s u g g e s t e d f o r M a l a c o s o m a p u l v i a l e ( W e l l i n g t o n 1 S 6 . 5 ) . C a p i n e r a e t a l . (1977) c o m p a r e d y o l k c o n t e n t i n l a r g e a n d s m a l l e g g s o f i x m a n t r i a d i s p a r a n d f o u n d t h a t l a r g e e g g s c o n t a i n e d more y o l k t h a n s m a l l e g g s , e v e n when e g g s w e r e s t a n d a r d i z e d f o r w e i g h t . The r e d u c t i o n i n e g g w e i g h t o v e r t h e o v i p o s i t i o n p e r i o d s u g g e s t s t h a t l a t e r e g g s a r e i n some s e n s e l e s s " f i t " . Hy d a t a a n d t h o s e o f H a r v e y (1977) f o r p u p a l w e i g h t s o f l a r v a e f r o m l a t e r b a t c h e s i n d i c a t e t h a t t h i s a s s u m p t i o n i s u n j u s t i f i e d . H a r v e y i n f a c t f o u n d b e t t e r s u r v i v a l i n l a t e r b a t c h e s . T h u s , g i v e n s u i t a b l e r e a r i n g c o n d i t i o n s , l a t e r 47 batches can be expected to be at l e a s t as successful as e a r l i e r batches. Shen rearing conditions are l e s s than i d e a l , egg s i z e may have an important e f f e c t on s u r v i v a l . Figure 4 suggests a lower hatching success f o r l a t e r egg batches at low temperatures. Capinera et a l . (1977) found that yolk became depleted at high temperatures, and a s i m i l a r yolk depletion at low temperatures could be responsible f o r my r e s u l t s - More experiments are necessary to est a b l i s h i f l a r v a l s u r v i v a l and pupal weight d i f f e r s i g n i f i c a n t l y between e a r l y and l a t e batches when c l i m a t i c factors are introduced. I t i s c l e a r from t h i s study that large year to year fluctuations i n pupal weight i n f i e l d populations result from immediate response to environmental conditions rather than a long term genetical response- In general, a genetic model or one which includes maternal e f f e c t s w i l l contribute l i t t l e to the understanding of size structure i n the population. However, a sudden , perhaps rare s h i f t i n climate or food na a v a i l a b i l i t y could dramatically a l t e r rearing conditions. I t i s only at these times that genetic or maternal influences w i l l play a major ro l e . 49 LITERATURE CITED Barbosa, P. and J.L. Capinera- MS- Population quality , d i s p e r s a l and numerical change in the gypsy moth , Lymantria dispar (L.). Bryant, E.H. 1977. Morphometric adaptation of the housefly Musca domestica L., i n the United States. Evolution 31:580-596. Campbell, B.J. 1975. Food plant spacing and the dispersal of the Cinnabar moth larva. MSc. Thesis, Department of Plant Science, University of B r i t i s h Columbia- 94pp. Capinera, J.L. and P. Barbosa. 1976. Dispersal of f i r s t s i n s t a r gypsy moth larvae i n r e l a t i o n to population guality. Oecologia(Berl-) 26:53-64. Capinera, J.L., P. Barbosa and J.H- Hagedorn. 1977. Yolk and yolk, depletion of gypsy moth eggs : Implications for population guality. Ann. Ent. Soc. Am. 70:40-42. 50 D a n t h a n a r a y a n a , w. 1 9 7 6 . E n v i r o n m e n t a l l y c u e d s i z e v a r i a t i o n i n l i g h t - b r o w n a p p l e m o t h , E p i p h y a s p o s t v i t t a n a ( W a l k . ) ( f o r t r i c i d a e ) , a n d i t s a d a p t i v e v a l u e i n d i s p e r s a l . O e c o l o g i a { B e r l . ) 2 6 : 1 2 1 - 1 3 2 -D e m p s t e r , J . P . 1 9 7 1 . The p o p u l a t i o n e c o l o g y o f t h e C i n n a b a r moth . O e c o l o g i a ( B e r l . ) 7 : 2 6 - 6 7 . G r e e n , W . Q . 1 9 7 4 . An a n t a g o n i s t i c h o s t / p l a n t s y s t e m : The p r o b l e m o f p e r s i s t e n c e . P h D . T h e s i s , D e p a r t m e n t o f Z o o l o g y , 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 , 2 4 7 p p . G r u y s , P . 1 9 7 0 . M u t u a l i n t e r f e r e n c e i n B u p a l u s p i n i a r i u s ( L e p i d o p t e r a , G e o m e t r i d a e ) . P r o c . A d v . S t u d y I n s t . D y n a m i c s Number s P o p u l . ( O o s t e r b e e k , 1 9 7 0 } . P 1 9 9 - 2 0 7 . H a r v e y , G . T . 1 9 7 7 . Mean w e i g h t a n d r e a r i n g p e r f o r m a n c e o f s u c c e s s i v e e g g c l u s t e r s o f e a s t e r n s p r u c e budworm ( L e p i d o p t e r a : T o r t r i c i d a e ) . C a n . E n t . 1 0 9 : 4 8 7 - 4 9 6 . K l o m p , H . 1 9 6 6 . 2he d y n a m i c s o f a f i e l d p o p u l a t i o n o f t h e p i n e l o o p e r , B u p a l u s p i n i a r i u s 1 . ( L e p . , G e o m . ) . . A d v . E c o l . R e s . 3 : 2 0 7 - 3 0 5 . L e o n a r d , D . E . 1 9 7 0 . I n t r i n s i c f a c t o r s c a u s i n g g 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 o f P o r t h e t r i a d i s p a r f L e p i d o p t e r a : L y m a n t r i d a e ) . C a n . E n t . 1 0 2 : 2 3 9 - 2 4 9 . M e i j d e n , E . , v a n d e r . 1 9 7 6 . , C h a n g e s i n t h e d i s t r i b u t i o n o f T v r i a j a c o b a e a e d u r i n g t h e l a r v a l p e r i o d - N e t h - , J . Z o o l . 2 6 : 1 3 6 - 3 6 1 . M y e r s , J . H . 1 9 7 8 . B i o l o g i c a l c o n t r o l i n t r o d u c t i o n s a s g r a n d i o s e f i e l d e x p e r i m e n t s : A d a p t a t i o n s o f t h e C i n n a b a r moth t o new s u r r o u n d i n g s * i n P r o c . I V t h I n t e r . S y m p . On B i o l o g i c a l C o n t r o l o f H e e d s , T . E . F r e e m a n ( e d . ) . C e n t e r f o r E n v i r . P r o g . I n s t , o f F o o d a n d A g r i c . S c i . U n i v e r s i t y o f F l o r i d a , p 1 8 1 - 1 8 8 . , . Hyers, J.H. and B.J. Campbell. 1976. Di s t r i b u t i o n and dispersal i n populations capable of resource depletion. Oecologia (Berl. ) 24:7-20. Nagel, W.P. and D.L. Isaacson. 1974. l y r i a lacobaeae and Tansy Bagwort i n Western Oregon. J. Econ. Ent. 67:494-496. Philogene, B-J.B. 1975. Responses of the Cinnabar moth Hypocrita -jacobaeae to various temperature/photoperiod regimes. J. Insect Physiol. 21:1415-1417. fiose, D.J.M. 1972. Dispersal and q u a l i t y i n populations of Cicadulina species (Cicadellidae). J. Anim- E c o l . 41:589-609. Bose, S.D. 1978. Effect of d i e t on l a r v a l development, adult emergence and fecundity of the Cinnabar moth , Tvria  jacobaeae (L.) (Lepidoptera : A r c t i i d a e ) . MSc. Thesis Oregon State University 88pp. 53 Sanders, C.L. and G. S. Lucuik. 1975. Ef f e c t s of photoperiod and size on f l i g h t a c t i v i t y and oviposition in the eastern spruce bud-worm (Lepidoptera : Tortricidae) Can. Ent. 107: 1289-1299. Schoener, T-H. and D.H. Janzen. 1968. Notes on environmental determinants of t r o p i c a l versus temperate insect size patterns. Amer. Natur- 102:207-224. Shiga, M. 1977. Population dynamics of Malacosoma neustria testacea (Lepidoptera :Lasiocampidae) : S t a b i l i z i n g process i n a f i e l d population. Bes- Popul. Ecol. 18:284-301-Sweeney, B. W. and R.L. Vannote. 1978- Size variation and the d i s t r i b u t i o n of hemimetabolous aguatic insects: Two thermal eguilbrium hypotheses. Science 200:444-446. Wellington, W.G. 1965. Some maternal influences on progeny guality i n the western tent c a t e r p i l l a r , Malacosoma pluviale (Dyar). Can. Ent. 97:1-14-

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