Self-injection of a dipteran parasitoid into a spider

A host invasion strategy hitherto unknown from other insect parasitoids was observed in the dipteran Acrocera orbicula (Fabricius) (Diptera: Acrocerid ae) parasitizing the wolf spider, Pardosa prativaga (L. Koch) (Araneida: Ly cosidae). In laboratory experiments the free-living first instar acrocerid larvae attached themselves firmly to the spiders' integument by the mouthpa rts, cutting a tiny hole through the integument. No first instar larvae inv aded the host. A week later the parasitoids molted, and a small, flexible, and glabrous second instar larva left each of the attached first instar exu viae and invaded the host through the attachment hole of the first instar l arva. The novel host invasion pattern observed may reduce physical damage t o the host in the initial phase of endoparasitism, enhancing parasitoid sur vival.