THE INFLUENCE OF CLUTCH SIZE ON SURVIVAL AND REPRODUCTIVE POTENTIAL OF HESSIAN FLY

The clutch size laid by Hessian flies (Mayetiola destructor Say) (Dipt era: Cecidomyiidae) was manipulated over a range of 1 to 30 eggs on si ngle wheat plants (Triticum aestivum, L.). Pupae developing from egg c lutches were removed from plants, counted and reared through to adult eclosion. Wing lengths of adult males and females were recorded and us ed as an indicator of body size. Survival to pupal and adult stages, a s well as mean wing length of resulting males and females, decreased a s clutch size increased. Wing length of females from clutches showed a positive linear relationship with potential fecundity. The benefits o f small clutches for a female Hessian fly's offspring are discussed in the context of the foraging behaviour of the ovipositing female. We p redict that under high probabilities of survival and availability of h ost plants, females will lay smaller-sized clutches per plant. However when the probability of survival is low and host plants scare, the fe male will respond by laying larger-sized clutches.