A series of laboratory tests was conducted on the face fly, Musca autumnalis De Geer, using a specially designed compartmentalized cabinet that would allow 6 different temperatures to be maintained simultaneously. The temperatures used in the test were: 100, 95, 90, 85, 80, and 70[degree] F. It was observed that pupae exposed to high temperatures (95 or 100[degree] F) and low temperatures (70[degree] F) resulted in poor adult emergence. Optimum emergence occurred at 85[degree] F. Age of the pupae was a definite factor. Four- and 5-day-old pupae were much less affected by extremes in temperature than 1- and 2-day-old pupae. Adult face fly longevity decreased with an increase in the temperature. The results from the production of F1 progeny from a known number of parent adults indicated that the optimum temperature was 80[degree] F. Higher temperatures (85-100[degree] F) or lower temperature (70[degree] F) resulted in a decreased production of progeny. It is thus concluded that temperature might be a factor in the distribution of this insect in North America.