Influence of food deprivation on foraging decisions of the parasitoid Bathyplectes curculionis (Hymenoptera : Ichneumonidae)

As adults, many parasitoid wasps require carbohydrates for reproduction and self-maintenance. Consequently, many adult female parasitoids that require carbohydrate foods located at a distance from host patches face a trade-of f between searching for hosts and food. In a series of experiments using a Y-tube olfactometer, we explored how hunger affects the foraging decisions of Bathyplectes curculionis (Thomson), a parasitoid of alfalfa weevil larva e. In particular, we tested whether an unfed parasitoid female is more like ly to search for food while a fed female is more likely to initiate host-se arching by first orienting to odors from the plants on which the host insec t feeds. When offered a choice between odors of the weevil's host plant fol iage (alfalfa, Medicago sativa L.) and a flower commonly found in the alfal fa field habitat (dandelion, Taraxacum officinale Weber), unfed female wasp s preferred the floral odor and fed wasps preferred odors of the host plant . The wasps preferred odors of inflorescences of dandelion over those of ph acelia, Phacelia tanacetifolia Bentham, a plant not found in alfalfa fields . Both fed and unfed wasps, however, responded positively to phacelia odor when offered against a control. When the wasps were given the choice betwee n phacelia flowers and alfalfa foliage, neither unfed nor fed wasps express ed a preference for either odor. An important consideration in introduction and conservation of parasitoids in biological control is a parasitoid's va rying responsiveness to host-habitat and floral odors as influenced by phys iological state.