HOST-SEARCHING BEHAVIOR OF VENTURIA-CANESCENS (GRAV) (HYMENOPTERA, ICHNEUMONIDAE) - INTERFERENCE - THE EFFECT OF MATURE EGG LOAD AND PRIOR BEHAVIOR

The foraging behavior of Venturia canescens, a solitary endoparasitoid of lepidopteran larvae, was investigated in the laboratory. Females w ith a greater number of mature eggs in their ovarioles and oviducts pa rasitized a greater number of hosts and won a greater proportion of en counters with other searching females. Wasps which had been exposed to hosts prior to an experimental trial lost a higher proportion of agon istic encounters with conspecifics than wasps which had no prior expos ure to hosts. The behavior of a wasp at the time of the encounter infl uenced the outcome of the encounter. Wasps involved in active search o f the host medium with the ovipositor (''probing'') were more likely t o win encounters than wasps in any other behavioral category. In a sit uation where the agonistic encounter was between two probing wasps, bo th contestants were equally likely to win. Results are discussed in th e light of the idea that mutual interference arises, in this species, as a result of agonistic encounters between searching females and rece nt dynamic-programming models which suggest that parasitoid ovipositio n should be influenced by mature egg load.