none Among insect parasitoids, superparasitism is said to occur when a second clutch of eggs is laid on a previously parasitized host. Ovicide occurs when a parasitoid destroys a clutch of eggs laid on a host by a previous female. Here, general models are constructed to predict the conditions which favor superparasitism and ovicide. Major predictions for the ovicidal model were that ovicide is more likely to occur if the time necessary to kill eggs is short, if travel times and the proportion of parasitized hosts increases and if the competitive advantage of a first clutch is large. The predictions of the models were tested by examining superparasitism and ovicide in Bracon hebetor (Say), a gregarious, ectoparasitoid of phytisiine moths. Using a wild and eye color mutant of B. hebetor to distinguish first and second clutches, it was found that the competitive advantage of a first clutch over a second clutch increased with the time between ovipositions. Patterns of superparsitism and ovicide in B. hebetor were in qualitative agreement with the major predictions of the model. Most notably, ovicide increased in frequency with a decrease in the overall rate of host encounter and an increase in the proportion of parasitized hosts encountered.