Adult response of face flies,Musca autumnalisDe Geer, to diapause-inducing stimuli was tested. Treatment of larvae and pupae with four temperature and photoperiod combinations had statistically significant effects on subsequent diapause in the adults. Larvae reared in a cool, short-day regime (15°C, 10:14 [L:D]), yielded some flies that showed arrested ovarian development and high levels of hypertrophied fat body even when placed in a warm, long-day regime (24°C, 14:10 [L:D]), which normally favors ovarian development. Diapause induction in adult face flies depended largely on environment, but our data showed that the larval and pupal environments also had significant effects on subsequent reproductive or diapause development.