Cronin, J. T. 1989. Inverse density-dependent parasitism of the evergreen bagworm (Lepidoptera: Psychidae). Environmental Entomology 18: 403-407.


This paper reports the results of a controlled manipulative experiment with the bagworm, Thyridopteryx ephemeraeformis (Haworth), on eastern redcedar, Juniperus virginiana L., to determine whether parasitism is density-dependent. Parasitoid foraging behavior indicated that two spatial scales were appropriate: individual trees and small patches of trees. Percentage of parasitism by Itoplectis conquisitor (Say) declined significantly as the density of female bagworms on individual trees increased. Although mathematically possible, this inverse density-dependent response appears too "vague" to promote the stability of the bagworm-I. conquisitor system. Other factors that may be involved in the regulation or control of the bagworm are discussed.

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