Thermal and Photoperiodic Responses in Aestivasting Pupae of Dictyoploca japonica(Lepidoptera:Saturniidae)

Abstract

At Hirosaki (40.5°N), larvae of Dictyoploca japonica pupate in late June to mid July. Pupae aestivate and adults eclose mainly in September. Under naturally changing thermal conditions in darkness, the pupal duration was negatively correlated with the date of pupation. When pupae were kept at constant temperature, adult eclosion was delayed, and the pupal mortality and variation in pupal duration increased, as temperature rose from 21 to 30°C. When pupae were transferred from a low (16°C) to a high (25°C) temperature, adults eclosed earlier than they did at either constant 16 or 25°C. The reverse transfer (from 25 to 16°C) exerted a delaying effect. High temperature therefore intensified or decelerated the completion of the early phase of pupal diapause compared with low temperature, but the later phase seemed to be completed faster at 25°C than at 16°C. At 29°C pupal development was accelerated by short days and retarded by long days. Both temperature and daylength are probably responsible for timing adult eclosion in autumn.