Late autumn occurrence of non-diapause male adults in various geographic populations of a pierid butterfly, Eurema mandarina

Abstract

ABSTRACT Adult-overwintering insects show diversity in the occurrence of reproductive diapause of males. Mating can occur both before and after winter in different species, and pre-winter mating allows males to reproduce without overwintering. In a pierid butterfly, Eurema mandarina, both diapause and non-diapause male adults emerge in the late autumn generation. Diapause females mate with non-diapause males before winter and re-mate with diapause males the following spring. Although this species is distributed from sub-tropical regions to cool-temperate regions, the geographic variation of this characteristic mating system has not been examined. A rearing experiment and a field survey were conducted to determine the geographic patterns of the mating system of the late autumn generation of E. mandarina for various populations from sub-tropical to cool temperate regions. Non-diapause males were observed in the late autumn generation in all populations examined. The frequency of pre-winter mating of females was not correlated with latitude. These results show that the mating system of the late autumn generation is similar among various populations distributed over a wider range, suggesting that the characteristic mating system may be evolutionarily stable.