Hyperparasites of the Gypsy Moth (Lepidoptera: Lymantriidae): Field Attack Patterns on Cotesia melanoscela (Hymenoptera: Braconidae) at Different Host Densities and on Different-sized Host Clumps

Abstract

Laboratory-reared cocooned larvae of Cotesia melanoscela (Ratzeburg) were exposed in the field in two ways. First, 50 cocoons in five clumps of 10 per clump were placed on trees at nine sites in different areas of Connecticut to relate hyperparasite attack frequency to natural population levels of C. melanoscela. Second, clumps of cocoons having 1, 5, and 10 individuals per clump were exposed at one site to see if differences in attack frequency occurred on different-sized clumps. Hyperparasites from six hymenopteran families were recovered. Results suggest that populations of the two most abundant groups of hyperparasites sampled, Dimmockia sp. (Hymenoptera: Eulophidae) and Gelis spp. (Hymenoptera: Ichneumonidae), were not noticably influenced by C. melanoscela abundance, probably because these hyperparasites have many alternate hosts. These same hyperparasites tended to attack several cocoons per clump of those found, and at east Gelis spp. attacked more clumps with 10 cocoons per clump than those with 1 cocoon per clump. However, for both hyperparasites, average parasitization of individual cocoons was not significantly different for different-sized clumps. Evidently the hyperparasites have low reproductive potentials or long handling times that may limit their ability to fully exploit aggregated hosts.