Cheng, who has volunteered as an association guide for many years, explains that they record the age of the butterflies so as to answer questions about whether the northern groups migrate south to overwinter, and if so, how.
擔任台灣蝴蝶保育學會解說義工多年的鄭菀菁表示，紀錄蝴蝶新舊程度，是為了解開北部族群是否會遷移到南部越冬的疑問。