ENVIRONMENTAL AND GENETIC-DETERMINANTS OF OVICIDE IN THE PARASITIC WASP BRACON-HEBETOR

Superparasitism occurs when a parasitoid lays a second clutch of eggs on a host previously parasitized by herself or a conspecific. Ovicide refers to a parasitoid destroying an existing clutch of eggs on a para sitized host before laying a second clutch. We investigated environmen tal and genetic determinants of ovicide in the parasitic wasp Bracon h ebetor. Characterization of egg-laying behavior revealed that B. hebet or commits ovicide during the host examination phase of oviposition. T he temporal costs of ovicide were found to be relatively small for fem ales that experienced low rates of host encounter, whereas the costs o f ovicide increased for females that experienced a high rate of host e ncounter. Individual wasps committed ovicide on conspecifically parasi tized hosts more frequently than on self-parasitized hosts. Manipulati on experiments suggested that B. hebetor females learn about their env ironment while foraging and commit ovicide on the basis of the travel time between successive hosts. Significant differences were also found in ovicidal behavior among laboratory and field populations of B. heb etor. The implications of our results for clutch size theory and the e volution of ovicide are discussed.