Delayed Response after Learning Associated with Oviposition Experience in the Larval Parasitoid, Cotesia kariyai (Hymenoptera: Braconidae)

The ability of female parasitoid wasps, Cotesia kariyai (Hymenoptera: Braconidae), to learn to recognize plant volatiles associated with an oviposition experience was investigated. First, we observed oviposition behavior of female wasps when encountering host larvae (Mythimna separata, Lepidoptera: Noctuidae). On their first encounters with host larvae, 96% of inexperienced female wasps showed oviposition behavior. Immediately afterward, and for 2 h after the first oviposition, wasp oviposition behavior was suppressed. Only 20–30% of wasps showed a second oviposition response, even after several encounters with a new host. Then, oviposition behavior gradually recovered 6 to 24 h after the first oviposition. At 6 h after the first oviposition experience, more than 80% of the wasps showed a second oviposition response when encountering a new host. Next, in a wind tunnel, we investigated the effect of time since first oviposition on wasp responses to host-infested plant volatiles. Female landings in response to volatiles of host-infested maize plants, Zea mays, showed a bell-shaped curve from 0 to 48 h after first oviposition. Eight hours after the first oviposition, the rate of landing by wasps was significantly higher than that of oviposition-inexperienced wasps. The ecological strategy explaining the effect of oviposition experience on olfactory responses of C. kariyai to host-infested plant volatiles is discussed.