Reinforcement mechanisms of olfactory conditioning during parasitization by the parasitoid Brachymeria intermedia (Hymenoptera: Chalcididae)

Through a single oviposition experience on their natural host in presence of vanilla odor, female Brachymeria intermedia were induced to drum and drill in a vanilla-scented artificial host. We examined which behaviors in the oviposition sequence mediated this conditioning: conditioning was most successful when odor exposure coincided with oviposition. Wasps were also conditioned when exposure to odor coincided with preoviposition drumming on the host, if drumming was followed by oviposition, and when exposure to odor coincided with drilling in an empty pupal case. Evidently, conditioning occurred through the formation of an association between the odor and the "aroused" state underlying host acceptance. These results support the hypothesis that conditioning occurs through a stimulus-arousal association rather than, as is generally assumed, through a stimulus-stimulus association.