Seasonal and spatial activity of hymenopterous pupal parasitoids (Pteromalidae and Ichneumonidae) of the house fly (Diptera: Muscidae) on danish pig and cattle farms

Abstract

Two pig farms, two dairies, and a combined pig and dairy farm in Denmark were relative abundance sampled weekly from April to December 1997 to determine the distribution and relative abundance of Musca domestica L. pupal parasitoids. Nine parasitoid species were collected in the study, including Spalangia cameroni Perkins, S. nigripes Curtis, S. subpunctata Forster, S. nigra Latrielle, Muscidifurax raptor Girault and Sanders Nasonia vitripennis. (Walker) Pachycrepoideus vindemiae (Rondani), Urolepis rufipes (Ashmead), and Phygadeuon fumator Gravenhorst. S. nigra had not previously been recorded as a parasitoid on M. domestica pupae in Denmark. Among the five farms, S. carneroni was the most abundant species collected indoors, whereas M. raptor dominated outdoors in the manure heaps. Maximum activity of parasitoids was observed in late summer, which corresponded well with peaks in temperature and fly density. S. cameroni and M. raptor were active from spring to fall, whereas the other species occurred more sporadic and in lower numbers. The overall rate of parasitism was low, ranging from 5.1 to 13.1% among the farms. Spatial distribution of the three most abundant species at indoor sites revealed that M. raptor primarily searches for fly pupae in the illuminated areas of the stable environment, whereas S. cameroni and S. nigripes were randomly distributed.