Aedes togoi (Theobald) from Vancouver, B.C. may enter diapause in either the egg or the larval stage. Larval diapause occurred in the 4th instar, when immatures were maintained at 16°C or less, at photoperiods shorter than 12h light/day. The critical photoperiod was calculated as LD 10.9:13.1 at 16°C. Larvae which did not pupate after 40 days at the experimental conditions were assessed as being in diapause. Non-diapause larvae reached the pupal stage in 17-20 days at 16°C. At 14°C, 100% of the larvae diapaused at LD 10:14. Temperatures of 18°C or higher, at LD 10:14, resulted in no larval diapause. Embryonic diapause resulted when immatures, adults and eggs were maintained at temperatures ranging from 22 to 28°C, at photoperiods shorter than 15h light/day. The critical photoperiod was calculated as LD 15.3:8.7 at 25°C, and LD 14.4:9.6 at 22°C. There was no diapause when the population was maintained at 24°C LD 16:8. An experiment was conducted to determine if a simulated dawn/dusk of 90 minutes/day would increase mating success. After three days at the experimental conditions, there was no difference in mating success between populations of males and females maintained with a dawn/dusk period and those maintained at the same photoperiod where the light/dark change was abrupt. / 1986