Life expectancy and egg load affect oviposition decisions of a solitary parasitoid.

Life-history theory predicts that animals should be sensitive to both the amount of resources available and life expectancy in making reproductive decisions. Because it is easier to control the mortality of insect parasitoids (insects whose larva develop in or on another insect) than many other groups of animals, the best tests of these predictions have used them. However, because of the inter-correlation of several of the variables of interest, much of this evidence is equivocal, and experimental manipulations have failed to isolate the most important factors. Here we report an experiment which circumvents such problems by comparing the superparasitism rates of fed and starved parasitoids. By using the asexual solitary hymenopteran parasitoid Venturia canescens, we demonstrate that starved wasps with a reduced life expectancy lay eggs in low-quality hosts more frequently than those with a greater expected lifespan, as do parasitoids with higher egg loads and hence more resources available for reproduction.