Canadian Forest Service Publications
Behavior of the parasitoid Pleolophus basizonus (Hymenoptera : Ichneumonidae) in response to changes in host and parasitoid density. 1972. Price, P.W. The Canadian Entomologist 104: 129-140.
Issued by: Laurentian Forestry Centre
Catalog ID: 15827
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A synthesis of observations on density-dependent interactions in parasitoid populations is attempted, working from the particular aspects of discrimination against parasitized hosts and detailed observations on parasitoid behavior, to more general aspects of parasitoid ecology, dispersal, distribution, and response to host populations. Females of Pleolophus basizonus (Gravenhorst) are able to discriminate against parasitized hosts of Neodiprion swainei Middleton between narrow limits (mean densities of 0.4 to 1.4 eggs per cocoon) set by the probability of a female finding an unparasitized host. They show mutual interference in egg laying at high parasitoid:host ratios, and a density-dependent escape reaction to adult parasitoid density. These behaviors all result from the recognition of repellent trail odors left by searching females. Response of individual females to high parasitoid densities may therefore lead to dispersal, the occupation by the population of more, but not so favorable habitats, and an apparent density-independent response to host populations.