Egg Diapause in Aedes Triseriatus (Diptera: Culicidae): Geographic Variation in Photoperiodic Response and Factors Influencing Diapause Termination1

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Abstract
Critical photoperiod for induction of egg diapause in geographic strains of Aedes triseriatus increased 1 h for each increase in latitude of 4.2°, over a range of 30–46°N latitude. Photoperiodic response was reduced or absent in strains from 28–30°N lat. and in highly “laboratory-adapted” strains of northern or southern origin. Absence of diapause in a Florida strain showed discrete inheritance with segregation, suggestive of regulation by a major recessive genetic factor. In the laboratory, egg diapause could be terminated in an Indiana strain by (1) exposure to short days at 4 °C, (2) prolonged exposure to long days at 21 °C, or (3) most rapidly by long-day treatment following storage at 4 °C. In field populations prolonged exposure to low temperature is probably responsible for termination of egg diapause.