小懒虫你！给你找个链接，见内。蝴蝶飞到哪，毛毛虫在哪。再飞，再产卵。。。徙迁路线依据它们的食物来源而走，几千英里的往返。

https://en.m.wikipedia.org/wiki/Monarch_butterfly

Like all Lepidoptera, monarchs undergo complete metamorphosis; their life cycle has four phases: egg, larva, pupa, and adult. Monarchs transition from eggs to adults during warm summer temperatures in as little as 25 days, extending to as many as seven weeks during cool spring conditions. During their development, both larvae and their milkweed hosts are vulnerable to weather extremes, predators, parasites, and diseases; commonly fewer than 10% of monarch eggs and caterpillars survive.