Differing Success of Defense Strategies in Two Parasitoid Wasps in Protecting their Pupae Against a Secondary Hyperparasitoid

During their larval development, endoparasitoids are known to dispose of host resources in several different ways. Some parasitoid wasps consume most or all tissues of the host, whereas others consume a small fraction of host resources and either ensure that the hostmoves away from the pupation site or allow the host to remain close to the parasitoid cocoon(s). Using a single host species, Mythimna separata Walker (Lepidoptera: Noctuidae), this study compares the success of the two pupation strategies in the solitary parasitoids Microplitis sp. and Meteorus pulchricornis Wesmael (Hymenoptera: Braconidae) against attack from a secondary hyperparasitoid,Gelis agilis F. (Hymenoptera: Ichneumonidae). The caudal appendages of M. separata caterpillars parasitized by Microplitis sp. remain physically attached to parasitoid cocoons and the caterpillars behave aggressively when disturbed. However, afterMe. pulchricornis larvae emerge from caterpillars of their host, M. separata, the parasitoid larvae pupate in cocoons that are suspended by a single thick thread that hangs 1Ð2 cm from under a leaf. In choice tests conducted in petri dishes, signiÞcantly fewer cocoons ofMicroplitis sp. attended by caterpillars than unattended cocoonswere hyperparasitized byG. agilis. By contrast, Me. pulchricornis cocoons that were hanging from corn, Zea mays L., plants were hyperparasitized as frequently as those which were attached to leaves. We discuss the potentially different selection pressures generated amongnatural enemies such as predators andhyperparasitoids in determining optimal pupal defense strategies in primary parasitoids.