Effect of the ectoparasite Necremnus breviramulus (Hymenoptera : Eulophidae) and its venom on natural and factitious hosts

Prepupae of Hypera eximia (LeConte) (Coleoptera: Curculionidae), a natural host, and prepupae of factitious insect hosts were tested for their physiol ogical responses to stinging Ly the gregarious ectoparasite, Necremnus brev iramulus Gahan (Hymenoptera: Eulophidae), and to injection with an extract of the venom gland tissue dissected from the lower reproductive tract of th e female parasite. The arrestment of development produced by N. breviramulu s venom was expressed in the natural host, H. eximia, and in all insects te sted outside the natural host range of the parasite (Coleoptera: Curculioni dae, Cerambycidae, and Chrysomelidae; Lepidoptera: Plutellidae and Noctuida e). Arrestment activity was found to he associated with the aqueous extract of the venom apparatus, and the response was shown to be dose-dependent. T he protein composition of the venom from N, breviramulus differed from othe r eulophids tested and did not contain the molt-arresting protein found in Euplectrus sop. The difference in venom proteins may account for the differ ent physiological effects and host range of these eulophid parasites.