Seasonal Polyphenism in a Subtropical Population of Eurema hecabe (Lepidoptera, Pieridae)

A subtropical population of Eurema hecabe shows seasonal changes in wing color-pattern (summer and autumn morphs). In the field, the forewingupperside coloration changed seasonally independent of hibernal arrest, although the magnitude of the change was small. There was a sexual difference in expression of seasonal morphs. Photoperiod and temperature were responsible for the seasonal morph determination. A long day of 13 hr or more induced the summer morphs whereas a short day of 12 hr or less the autumn morphs, and this photoperiodic effect was clearer at 20℃ than at 25℃. The response to short days was more pronounced in males than in females, and moreover autumn morph males were produced at 20℃ even under long days. In female butterflies, the seasonal morph change was associated with a change in temporal pattern of ovarian egg maturation. Climatic adaptation of E. hecabe is discussed by comparing the subtropical and temperate populations.