Monarchs fly a multigenerational circle around the eastern United States every year. In the fall the last generation heads for Mexico.
When we think of the great animal migrations, we tend to think of great animals--creatures like caribou or wildebeests. But one of the most spectacular movements of life is undertaken by the four-inch-wide monarch butterfly. Every fall tens of millions of monarchs disappear from the United States. Until the mid-1970s, no one knew where they went; it was only then that an amateur lepidopterist found their hiding place in a high mountain range in Mexico. Researchers now know that all monarchs east of the Rockies fly down to Mexico in vast swarms at speeds of up to 30 miles an hour and altitudes of up to a mile. (Western monarchs head for southern California.) After traveling as much as 2,200 miles, they settle down on 30 sites located in ...
