The ability to learn plant volatiles in Cotesia kariyai females was examined by wind tunnel bioassays. Searching experience on a host‐infested corn plant increased subsequent flight responses of females to the infested plant. Females experiencing host by‐products together with the volatiles extracted from infested leaves one time showed an increased response. However, such behavioral changes were not observed in females which experienced only the host by‐products or the volatiles. Thus, the increased response is considered to be preference learning. Multiple experiences of C. kariyai with host by‐products together with the volatiles did not increase their flight response to the volatiles. Furthermore, this learned response gradually decreased within 2 days. These behavioral modifications based on experience would be advantageous for C. kariyai to locate their polyphagous hosts efficiently.

An azole compound is considered to be a good probe for analyzing the binding affinity with various cytochrome P450 (CYP) proteins because of its coordination ability regarding the heme iron in the proteins. Eighteen azole compounds including commercial fungicides were examined for their binding to rat liver microsomal CYP2B and CYP3A using a type II spectral change. The binding affinities determined were analyzed in relation to the molecular properties of the azole compounds. Good correlation with the bilinear model was observed between the binding affinities and the partition coefficient (log P). The model suggested that the optimum log P values of the azole compounds were nearly the same for these two CYPs. The sequence homology of amino acid residues around the substrate recognition site is significantly high between CYP2B and CYP3A. It was reported that sizes of the binding pocket in CYP2B and CYP3A are not much different. These explain why the optimum log P values in the correlation equations for CYP2B and CYP3A was nearly the same.

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Learning of host-induced plant volatiles by Cotesia kariyai females was examined with synthetic chemicals in a wind tunnel. Wasps were preconditioned by exposure to volatiles and feces simultaneously. A blend of four chemicals, geranyl acetate, beta-caryophyllene, (E)-beta-farnesene, and indole, which are known to be specifically released from plants infested by host larvae Mythimna separata (host-induced blend), elicited a response in naive C. kariyai, but did not enhance the response after conditioning. A blend of five chemicals, (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexen-1-yl acetate, beta-myrcene, and linalool, which are known to be released not only from plants infested by the host larvae, but also from artificially damaged plants or undamaged ones (unspecific blend), elicited little response in naive wasps, but significantly enhanced the wasps' response after conditioning. With a blend of the above nine chemicals, wasps could learn the blend at lower concentrations than they did in the nonspecific blend. Hence, both the host-induced and nonspecific volatile compounds appear to be important for C. kariyai females to learn the chemical cues in host location.

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