Host movement initiates oviposition behavior of Meteorus pulchricornis, a braconid parasitoid of free-living lepidopteran larvae

Meteorus pulchricornis is a solitary endoparasitoid of various lepidopteran larvae that attacks free-living hosts exposed on plant foliage. We tested the necessity of host movement for oviposition behavior in M. pulchricornis using dummy hosts as well as natural host larvae (Spodoptera litura). We quantified the occurrence of three steps in oviposition behavior, i.e., host orientation, oviposition stance, and oviposition attack, to natural hosts under light and dark conditions. We also examined the incidence of these behaviors on natural hosts, moving dummy hosts, and motionless dummy hosts under light conditions. Few successful attacks occurred on natural hosts under dark conditions and no oviposition attempts were made against motionless dummy hosts. These results indicate that visual cues from moving host larvae are necessary for successful oviposition. Furthermore, host movement seems important for female wasps to orient the ovipositor toward the host body, since the location of the oviposition attack on natural hosts changed markedly with the mode of host movement.