Otsunencho - Otsunencho

...They overwinter as non-diapausing larvae, growing slowly through the winter by feeding on the leaves of legumes such as milk vetch and clover in sunny spots. Some individuals emerge in early spring, so in the past they were thought to overwinter as adults and were also called Otsunencho (overwintering butterflies), but unlike the Yamanoe and Eurema species, they are not capable of overwintering as adults. Adults that emerge at low temperatures tend to be dark in color and small.

*Some of the terminology that refers to "Otsunenchou" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…非休眠幼虫で越冬し，日だまりのレンゲやクローバーなどマメ科の植物の葉を食べて冬も緩慢に成長する。早春に出現する個体があるので昔は成虫越冬と考えられ，オツネンチョウ(越年蝶)とも呼ばれたが，ヤマキチョウ類，キチョウ類のような成虫越冬の可能性はない。低温時に羽化した成虫は濃色，小型の傾向がある。…

※「オツネンチョウ」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報