Discrimination Between Parasitized and Unparasitized House Fly Pupae by Females of Nasonia vitripennis (Walk.) (Hymenoptera: Pteromalidae)

Abstract Females of Nasonia vitripennis (Walk.) (Hymenoptera: Pteromalidae) laid fewer eggs on parasitized than on unparasitized pupae of the house fly, Musca domestica L. Chemical and/or physical conditions of parasitized pupae are detected by the female’s ovipositor, causing this restraint. These conditions may in part result from the host’s death, caused by earlier parasitization, but other factors are also involved. These may include venom injected by the female parasite before she lays, and internal injury to the host resulting from insertion of the parasite’s ovipositor. The female parasite does not discriminate because of physical or chemical traces on the surface of parasitized puparia, of eggs or a surface wound on the pupa, or of absence of heart beat in the pupa.