Some Ichneumonid-Sarcophagid Interactions in the Gypsy Moth Porthetria dispar (L.) (Lepidoptera: Lymantriidae)

Abstract

Four ichneumonid species, Itoplectis conquisitor (Say), Pimpla pedalis Cress., Theronia atalantae (Poda), and Theronia hilaris (Say), were seen attacking the gypsy moth, Porthetria dispar (L.), in the Town of Glenville, Schenectady County, New York. These species stung and killed many more host pupae than they successfully parasitized (success here being measured by the development of an ichneumonid offspring within the host). The ratio between the total number of hosts stung by ichneumonids and the number of ichneumonid offspring emerging was different for each of the three primary ichneumonids studied, ranging from 4 to 1 for T. atalantae to more than 200 to 1 for I. conquisitor.The sarcophagids associated with the gypsy moth, although apparently parasitic, are largely scavengers. Their attacks almost always follow those of ichneumonids. Since the sting by an ichneumonid kills the host but is not always discernible, the number of pupae containing sarcophagid larvae has been used to, indicate the true effects of ichneumonids on the host population.