HYMENOPTEROUS PARASITOIDS OF FILTH FLY (DIPTERA: MUSCIDAE) PUPAE IN CATTLE FEEDLOTS

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Abstract
Results of a 2-year survey in Alberta, Canada, identified a parasitoid fauna of filth flies distinct from that generally reported for cattle confinements in the United States. Twenty-two feedlots were surveyed using freeze-killed sentinel house fly pupae. Parasitism averaged 0.25%. Ten species of hymenopterous parasitoids were recovered. As a percentage of the total number of pupae parasitized, these species wereMuscidifurax raptorGirault & Saunders (37.4%),Trichomalopsis sarcophagaeGahan (23.9%),Urolepis rufipes(Ashmead) (18.5%),Muscidifurax zaraptorKogan & Legner (6.9%),Nasonia vitripennisWalker (6.5%),Trichomalopsissp. (3.7%) (Pteromalidae),Phygadeuonsp. (2.9%) (Ichneumonidae),Dibrachys cavus(Walker) (0.1%) (Pteromalidae),Synacrasp. (0.1%) (Diapriidae), and an unidentified Braconidae (0.1%). No differences were detected among natural regions of the province. Three categories of seasonal activity are identified which expand on previous groupings of species by their geographic distributions. The abundance ofT.sarcophagaeand rarity of species ofSpalangiaLatreille, 1805 are in marked contrast to results of surveys conducted in the United States. This difference suggests that species used to manage populations of pestiferous flies associated with livestock in the United States could be inappropriate for use in Canada.