Changes of diapause and cold hardiness in the Shonai ecotype larvae of the rice stem borer, Chilo suppressalis Walker (Lepidoptera: Pyralidae) during overwintering.

Larvae of the Shonai ecotype of the rice stem borer, Chilo suppressalis, were in diapause until October when the ambient temperature was relatively high and most of the larvae terminated diapause in November before winter.The cold hardiness of field-collected larvae was low at the diapause stage, but relatively high at the post-diapause stage.Glycerol was scarcely detected at the diapause stage, but its content increased at the post-diapause stage.Conversion between glycogen and glycerol was found in diapausing larvae during temperature acclimation (0-30°C), but a time lag between glycogen loss and glycerol increase was detected under field conditions.The results obtained for the Shonai ecotype are compared with those of the other main ecotype of this species, the Saigoku ecotype.