Host species and size as factors in parasitism by Muscidifurax spp. and Spalangia spp. (Hymenoptera: Pteromalidae) in the field

Parasite host preference was assessed in a caged-layer poultry house during two seasons in southern California. Fiberglass mesh bags containing equal numbers of Musca domestica L. pupae and Fannia canicularis (L.) pupae or large and small M. domestica pupae were buried in manure in natural fly pupation sites. Equal numbers of parasites emerged from the M. domestica and from the F. canicularis hosts. Parasites did not discriminate significantly against small M. domestica hosts when they were paired with large M. domestica hosts. Sex ratios of emerged Muscidifurax spp. and Spalangia spp. were significantly more female-biased from M. domestica hosts than from F. canicularis hosts during 1985. Sex ratio of emerged Muscidifurax spp. was significantly more female-biased from large M. domestica than from small M. domestica , while Spalangia spp. did not significantly alter progeny sex ratio in response to host size.