Influence of Food Deprivation on Foraging Decisions of the Parasitoid Bathyplectes curculionis (Hymenoptera: Ichneumonidae)

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Abstract
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-off 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 larvae. In particular, we tested whether an unfed parasitoid female is more likely to search for food while a fed female is more likely to initiate host-searching by first orienting to odors from the plants on which the host insect feeds. When offered a choice between odors of the weevil's host plant foliage (alfalfa, Medicago sativa L.) and a flower commonly found in the alfalfa field habitat (dandelion, Taraxacum officinale Weber), unfed female wasps preferred the floral odor and fed wasps preferred odors of the host plant. The wasps preferred odors of inflorescences of dandelion over those of phacelia, 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 between phacelia flowers and alfalfa foliage, neither unfed nor fed wasps expressed a preference for either odor. An important consideration in introduction and conservation of parasitoids in biological control is a parasitoid's varying responsiveness to host-habitat and floral odors as influenced by physiological state.