An Extraserosal Envelope in Eggs ofPraon pequodorum(Hymenoptera: Aphidiidae), a Parasitoid of Pea Aphid

We describe an extraserosal envelope which surrounds the developing embryo of the parasitoid wasp,Praon pequodorumViereck (Hymenoptera: Aphidiidae). The envelope separates chorion and trophamnion and has no visible cellular structure. It is formed inP. pequodorumeggs deposited in aphids that are already parasitized by a different species of wasp (Aphidius erviandAphidius smithi), but not in singly parasitized and conspecifically superparasitized aphids. We propose that the envelope has a defensive function and protects the developing embryo against (physical) attack by a mandibulate first-instar larva of a potential competitor.