| Summary: | Embryonic diapause, which is determined by day-length, has been demonstrated in a multi-voltine mosquito, Aedes atropalpus (Coquillett). Experiments conducted under controlled temperature and photoperiod show that short-days, 8 hours to 14 hours light per 24 hour day, induce diapause in the autogenous Belleville strain of A. atropalpus. The effect of long photoperiods is shown to be independent of low temperatures therefore indicating that in nature the deposition of diapausing eggs in autumn is due to the influence of the shorter days experienced by the mosquitoes. Experiments also show that the sensitive stages for light reception are the fourth larval instar, pupa and adult. Two strains of A. atropalpus were studied, one being the autogenous strain from Belleville, Ontario (44*N latitude) and the other being the anautogenous strain form Austin, Texas (30*N latitude). The effects of photoperiod and diet on fecundity in autogenous A.atropalpus are discussed. The effect of photoperiod and temperature on the biting activity and ovarian development of anautogenous Culiseta inornata (Williston) showed that this species exhibits the phenomenon of "gonotrophic concordancy". Studies on the autogenous ovarian development in Aedes species at Churchill, Manitoba (58oN) showed that four species, A. communis (Degeer), A. nigripes (Zett.) A. impiger (Walker) and a. campestris (Dyar and Knab) are autogenous.
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