The effect of temperature on life history parameters of Muscidifurax raptorellus Kogan & Legner was determined and compared with species currently attacking fly pupae in feedlots and dairies in Alberta. Immature developmental times declined from 72 d at 15°C to 13 d at 30°C for females. Male developmental time averaged 96% of female developmental time. Immature survival ranged from 0.23 at 15°C to 0.93 at 25°C, then declined to 0.42 at 33°C. Emerging wasps averaged 0.60 female, with an average of 8.6 and 6.2 progeny produced per parasitized pupa in Musca domestica L. and Stomoxys calcitrans (L.). Female longevity declined from 11 to 5 d as temperatures increased from 15–33°C. Time to 50% progeny production followed a similar pattern. Lifetime progeny production increased from 28–37 progeny per female at 15°C to 85–120 at 20–25°C, then declined to 48–50 progeny per female at 33°C. The net reproductive rate increased from 1.8–2.3 females at 15°C to 39–48 females/female at 25°C, then declined to 13–15 females per female at 33°C. Mean generation time declined with temperature. The intrinsic rate of increase increased from 0.007–0.010 females/female/d at 15°C to 0.203–0.206 females/female/d at 30°C, then declined to 0.173–0.186 females/female/d at 33°C. M. raptorellus had lower lifetime progeny production, net reproductive rate, and intrinsic rate of increase at all temperatures compared with Muscidifurax raptor Girault & Sanders. Life history parameters of M. raptorellus compared favorably to those of Muscidifurax zaraptor Kogan and Legner at all but the highest temperatures, and also with those of Trichomalopsis sarcophagae Gahan at all temperatures. It does not appear that there is any climatic barrier to the use of M. raptorellus for inundative releases for fly control in Alberta.