Characteristics of a developmental arrestant in the venom of the ectoparasitoid wasp Euplectrus comstockii.

Parasitic Hymenoptera regulate their hosts in order to provide a suitable source of nutrition and dwelling for their offspring. Few regulatory factors known to cause a specific effect on the host have been structurally characterized. The larval ectoparasitoid Euplectrus comstockii Howard (Hymenoptera: Eulophidae) arrests larval-larval ecdysis in its lepidopteran hosts. Prior to oviposition, the female wasp inject a venom into the hemocoel of the host and that venom alone is effective in causing the arrestment. A venom gland-reservoir structure connected to the lower reproductive tract of the wasp contains a complex mixture of proteins. There are no obvious similarities among the electrophoretic banding pattern (native or denatured) for venom proteins of E comstockii and several other parasitic hymenopteran species. Venomous protein, separated by electrophoretic techniques, with a native mol. wt of c. 66,000, was capable of arresting larval-larval ecdysis in 4th instar larvae of Trichoplusia ni (Lepidoptera: Noctuidae). Nanogram quantities of the protein were sufficient to cause arrestment. The activity of the protein was sensitive to temperature, pH, organic solvent, and protease.