Diapause-like prolongation of larval duration under short-day photoperiod and low temperature conditions in the silver Y moth, Autographa gamma Linnaeus (Lepidoptera: Noctuidae)

Abstract

The silver Y moth, Autographa gamma is a well-known migratory insect pest without apparent diapause; however, it overwinters under cold conditions in Hokkaido, Japan. Middle stage larvae are found under deep snow in late winter in this area. To elucidate the winter-adaptation feature of the Hokkaido population, photoperiodic responses were examined at various temperatures (28, 23, 18, 13°C). There were few differences in the egg and pupal duration between under short-day (12L-12D) and long-day (16L-8D) photoperiods. However, larval duration greatly prolonged under short-day photoperiod than under long-day photoperiod at 13°C, due to the prolongation of the fourth larval instar.