Induction of odor preference in a specialist insect parasitoid

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This paper deals with the effect of associative and nonassociative odor conditioning on odor preference in a specialist larval parasitic wasp ofDrosophila melanogaster, Leptopilina boulardi. Differently experienced females were offered a choice between banana and strawberry odors in a four-armed olfactometer. Wasps that were allowed to oviposit in an odorless airflow before testing exhibited no significant response to the odors, whereas females with an oviposition experience in the presence of an odor clearly preferred the scent that they had experienced. Furthermore, exposure to strawberry odor after oviposition could also induce a preference for strawberry or banana odor, depending on the concentrations of both scents used for conditioning and testing. This effect was independent of the time elapsed between oviposition and strawberry exposure, suggesting that it was caused by nonassociative conditioning and not by backward associative learning. Exposure to banana odor after oviposition had no effect on females’ responses. Variations in odor concentrations also influenced the expression of associative learning, although to a much lesser extent.