Abstract
During the rearing on an artificial diet of Ostrinia furnacalis GUENÉE collected in Morioka (Iwate Prefecture), an abnormal sex ratio was found in some rearing containers which yielded predominantly or exclusively female moths. The population collected in Daiei (Tottori Prefecture) showed a similar phenomenon, whereas, the population of Koriyama (Fukushima Prefecture) and Kuroishi (Aomori Prefecture) showed a normal sex ratio. Some of the containers of the population of Sapporo (Hokkaido) 75 per cent of the population consisted of females, although there was no evidence of an abnormal sex ratio which is mainly induced by the death of male larvae at the early stage of development. However, a high percentage of eggs failed to hatch in the Daiei population, suggesting that a few males were killed during the embryonic stage. No significant differences in the period from hatching to 50 per cent moth emergence was found between the populations with a normal and abnormal sex ratio, respectively. The pupal weight of the populations with an abnormal sex ratio was somewhat smaller than that of the normal ones.
