none Filth fly pupal parasitoids were surveyed for 2 yr at four dairies in southern Alberta. Seven parasitoid species were recovered. Muscidifurax raptor Girault & Sanders, M. zaraptor Kogan & Legner, and Trichomalopsis sp. were the most abundant and were recovered in both years. Other species were Urolepis rufipes (Ashmead), Phygadeuon sp. Spalangia cameroni Perkins, and Dibrachys cavus (Walker). Parasitism of intact pupae was generally lt 2%, but exceeded 30% on one occasion. Parasitoids were active from May to October, with most activity during August. Seasonal patterns for M. raptor and Trichomalopsis sp. were not consistent both years and were probably influenced by excessive rainfall during June 1991 and relatively low levels of parasitism. Parasitoid activity increased with increasing temperature and was negligible at temperatures below 11 degree C.