摘要
黑脉金斑蝶是北美地区最常见的一种蝴蝶,它体形较大,因而又有"帝王蝶"之称。这种蝴蝶每年都会进行大规模的迁徙,原因是什么呢?一起到文章中寻找答案吧!
Monarchs are the only butterflies known to make two-way migrations,as birds do.The annual migration of the eastern North American monarch butterfly is the most highly evolved(进化)of any known species of their kind.
