Interspecific Differences in Host (Diptera: Muscidae) Size and Species Usage among Parasitoid Wasps (Hymenoptera: Pteromalidae) in a Poultry House

Fly pupae, primarily house fly (Musca domestica Linnaeus) and stable fly (Stomoxys calcitrans (Linnaeus)) (Diptera: Muscidae), were collected from a poultry house in northern Indiana, and parasitoid wasps developing in them were allowed to emerge. Fly pupae density, relative species abundance, and size varied with collection date. Four species of parasitoid wasps were reared from the fly pupae: Spalangia endius Walker, S. cameroni Perkins, S. nigroaenea Curtis, and Muscidifurax raptor Girault and Sanders (Hymenoptera: Pteromalidae). There was some evidence of differential host species and size usage among the wasp species; but the differences were small, and there was considerable overlap. Controlling for relative host species abundances, percent parasitism was independent of host species for S. endius and S. cameroni, but M. raptor emerged from house flies more frequently than expected by chance and stable flies less frequently than expected. S. endius emerged from larger hosts than did S. cameroni, despite S. endius being on average smaller than S. cameroni. This is the first study to examine host size differences among these parasitoid wasps.