The effect of temperature on the life history of Muscidifurax raptor Girault & Sanders was determined to develop relationships that could be used to improve simulation models of biological control. Immature developmental rates were influenced by temperature and sex. Males developed faster than females, and the developmental rate increased with temperature to 30°C, then declined. Immature survival was lowest at 15 and 33°C, and highest in the range 20–25°C. Sex ratio of emerging parasitoids averaged 72 and 55% from house fly, Musca domestica (L.), and stable fly, Stomoxys calcitrans (L.), pupae and increased with temperature. Female longevity, time to median oviposition, and lifetime progeny production declined as temperature increased. The net reproductive rate was lowest at 15 and 33°C, and greatest at 25°C. Mean generation time decreased with increasing temperature. The intrinsic rate of increase was highest at 30°C. M. raptor has a broad thermal preference which may account for its greater relative abundance and wider seasonal abundance in Alberta compared with other species of naturally occurring parasitoids.