DIAPAUSE AVOIDANCE INDUCED BY LOW-TEMPERATURE IN THE YELLOW-SPOTTED LONGICORN BEETLE, PSACOTHEA-HILARIS

The diapause-averting effect of low temperature on pre-diapause larvae was examined in the yellow-spotted longicorn beetle, Psacothea hilari s. Larvae that had been reared under diapause-inducing conditions (25 degrees C, L12:D12) were temporarily exposed to 10 degrees C for vario us periods, and returned to the initial condition. Diapause was not av erted by chilling for 15 days irrespective of the age of the larvae at chilling. After a 30-day chilling treatment, all of the 40- and 60-da y-old larvae averted diapause, while diapause was averted in only one- third of the 10- and 20-day-old larvae. None of the pre-diapause larva e chilled for 60 days entered diapause irrespective of the age at chil ling. With diapause avoidance, larvae that overwintered in earlier ins tars can start growing in earliest spring without any arrest; this phe nomenon probably subserves the synchronization of larval development i n a population.