Effects of mating on host selection by female small white butterflies Pieris rapae (Lepidoptera: Pieridae)
Mating might significantly affect the host selection behaviors of phytophagous insects. Here, we investigated the post-mating changes in behavioral and antennal responses of Pieris rapae (Lepidoptera: Pieridae) females to host plant volatiles. In two-choice bioassays using artificial plant models, mated females visited the model scented with synthetic blends (15-, 9-, or 6-components) of cabbage plant volatiles more frequently than the unscented control, whereas virgin females did not exhibit this preference. Because single compounds and the 3-component blend did not induce preferential visiting, mated females apparently utilized complex odor blends as their host-finding cue. Moreover, 2- to 4-day-old mated females visited the models, scented and unscented, more frequently than did their virgin counterparts. Therefore, mating enhanced the host-finding behavior of young females and their responsiveness to plant volatiles. Gas chromatography–electroantennographic detector analysis revealed that eight of the 15 compounds in the cabbage plant volatiles elicited responses from female antennae. However, post-mating and age-dependent changes in antennal responses were not detected. Because female peripheral (antennal) sensitivity to volatiles remained practically unchanged after emergence, post-mating changes in host selection might be attributed to changes in the central nervous system.