The effect of photoperiod on longevity of nondiapausing members of a species in the mosquito species complex Anopheles quadrimaculatus was tested in laboratory experiments. First-generation adults reared from 2 field collections showed the same trends: those reared under short photoperiod (8 h light: 16 h dark) lived longer than did those reared under long photoperiod (16 h light: 8 h dark). Adult metabolic rates were not consistently related to longevity. In adults reared from the first collection, metabolic rates were higher in long-photoperiod individuals but in adults reared from the second collection, metabolic rates were higher in short-photoperiod individuals. Longevity appears to be another of many insect features that are affected similarly by temperature and photoperiod.