Unlike most other insects in temperate climates, monarch butterflies cannot survive a long cold winter.  Every fall, North American monarchs fly south to spend the winter at roosting sites. Monarchs are the only butterflies to make such a long, two-way migration, flying up to 3000 miles in the fall to reach their winter destination.  Amazingly, they fly in masses to the same winter roosts, often to the exact same trees.  Their migration is more the type we expect from birds or whales than insects.  However, unlike birds and whales, individuals only make the round-trip once.  It is their children’s grandchildren that return south the following fall.

Some other species of Lepidoptera (butterflies and moths) travel long distances, but they generally go in one direction only, often following food. This one-way movement is properly called emigration. In tropical lands, butterflies do migrate back and forth as the seasons change. At the beginning of the dry season, the food plants shrivel and the butterflies leave to find a moister climate. When the rains arrive, the food plants grow back and the butterflies return.

To learn more about monarch migration and overwintering sites, and about how scientists study these phenomena, follow the links below.

How do monarchs know when to leave?

Where do the monarchs go?

How do monarchs find the overwintering sites?

How do scientists study migration?

References