GEOGRAPHICAL VARIATION OF PHOTOPERIODIC ADULT DIAPAUSE IN DROSOPHILA AURARIA

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The variation of photoperiodic adult diapause was studied in Drosophila auraria strains originating in Japan at latitudes from 33.8 to 43.1°N. All the differently-located geographical strains showed a photoperiodic diapause. The critical daylength of these strains fell between 12 and 14h. The diapause intensity increases with an increase in latitudes. The duration of diapause was shorter at a photoperiod of 12 or 6h than at one of 10 or 8h in all the strains. This is because the photoperiod of 12 or 6h is less effective as a stimulus for the maintenance of diapause.