Learning Influences Host Versus Nonhost Discrimination and Postalighting Searching Behavior in the Tephritid Fruit Fly Parasitoid Diachasmimorpha kraussii (Hymenoptera: Braconidae).

Compared with the extensive body of research on the olfactory behavior of parasitoids of leaf-feeding insects, less is known about the fine-tuning of olfactory behavior in parasitoids that use fruit-feeding insects as hosts. We investigated whether a tephritid fruit fly parasitoid, Diachasmimorpha kraussii (Fullaway) (Hymenoptera: Braconidae), could discriminate between odors of fruits infested by larvae of a host species, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), compared to fruits infested by non-host larvae, Drosophila melanogaster (Diptera: Drosophilidae). Female wasps showed a significant preference for nectarines infested with B. tryoni, over uninfested fruits or fruits infested with D. melanogaster. When wasps were given prior experience of host or nonhost infested fruit, females demonstrated an increased ability to discriminate between host and nonhost related odors, but only when they were conditioned on host-infested (as opposed to nonhost infested) fruit. Insects provided with both host and nonhost stimuli showed no greater discriminatory learning compared to those provided with the rewarding stimuli alone. Previous experience also influenced postalighting behavior. Naïve females, and females with experience ovipositing at the top of fruit, oriented preferentially to the top of fruits upon alighting, while those with experience ovipositing at the base of fruits showed a significant difference in orientation, with 70% of wasps orientating preferentially toward the base. Similar learning-related changes were seen in search time and probing behavior. We discuss how pre- and post-alighting learning fine-tunes the behavioral responses of foraging wasps to their local environment.