Larval Diapause in the Eastern Tree-Hole Mosquito, Aedes triseriatus1: Latitudinal Variation in Induction and Intensity

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Abstract
Larvae of Aedes triseriatus (Say) from 26 to 46°N latitude undergo 4th-instar diapause in response to short-day cool conditions. Both subtropical and northern populations have relatively greater incidence of continuous development at short photoperiods, whereas northern populations exhibit greater diapause at long photoperiods as well. Diapause intensity is relatively stronger in females and in the central area of the latitudinal range; intrapopulation variance is greatest at range extremes. The critical photoperiod (CP) for larval diapause increases only slightly with population latitude and much less than the corresponding CP increase for embryonic diapause. Embryonic diapause CP exceeds larval diapause CP, within populations, by at least 1 h from Atlanta, Ga., north, indicating that eggs are the primary overwintering stage. Larval diapause may be maintained in the North by the selective effects of unpredictable spring weather, whereas in southern populations having incomplete embryonic diapause, progressively milder winter conditions favor larval diapause and continuous development.