Supercooling Capacity and Cold Tolerance of the Wild Silkworm, Antheraea pernyi (Lepidoptera: Saturniidae)

Abstract

While wild silkworms have served humans for several thousand years, little attention on cold hardiness has been paid to these economically important species. In the present study, supercooling capacity and low temperature tolerance of Chinese oak silkworm, Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Saturniidae), an economic insect reared both for silk production as well as human food, were examined under laboratory conditions. The supercooling points (SCPs) of pupae dropped significantly from a mean of -15.6°C in prediapause to -20.1°C in diapause, and then increased to -17.5°C during postdiapause development. Sex and voltinism influenced body mass but had no significant effect on the SCP. Our data demonstrated that cold tolerance of A. pernyi is tightly linked to life stage. Exposure of eggs to -5°C for up to 8 h had no effect on the hatching rate, whereas silkworm larvae failed to break through the chorion and hatch following a 4-8-h exposure to -10°C. Mean SCPs of intact eggs and naked larvae one day before hatching were similar, -23.3°C and -22.3°C, respectively, indicating that chorion does not significantly affect SCP. Comparison of lower lethal temperature (LLT50) and SCP means suggested that both pupae and eggs of A. pernyi are chill intolerant. These data will improve our understanding of low temperature tolerance in this commercially important species.