Seasonal Adaptation in a Northernmost Population of Epilachna admirabilis (Colepotera : Coccinellidae) I. Effect of Day-Length and Temperature on Growth in Preimaginal Stages

Abstract

To understand how Epilachna admirabilis Crotch adapt to local climate of northern areas, beetles of Sapporo population were reared under various day-length and temperature conditions. Short-day photoperiod accelerated the growth for 1-st to 3-rd instar larvae, whereas strengthen winter diapause for the final 4-th instar larvae. In both responses, day-length affected quantitatively, and any critical day-length could not be determined. Due to these photoperiodisms, the ladybird population should be assured their univoltine cycle, to pass speedily younger larval stages in autumn and to enter diapause in the final instar larvae. In egg and pupal stages, on the other hand, no effect of day-length was observed, and threshold of development/thermal constant were 8.4℃/223℃-days for the egg, and 7.3℃/157℃-days for the pupa.