LIFE CYCLE OF THE NORTH AMERICAN MONARCH BUTTERFLY
Monarch butterflies born in Canada and the United States begin their
southward migration in the fall. Those west of the Rockies head for
various sites in California, while those east of the Rocky Mountains
fly all the way to Mexico. Some fly as many as 2,800 miles. There
is emerging evidence that some Western monarchs reach Mexico as well.
They start out one by one, but soon are joined by tens, then scores,
hundreds, thousands and tens of thousands of fellow monarchs. Roosting
together at night in trees and feasting on nectar from favorite flowers,
they build their fat reserves as they head toward Mexico, a place
to which they have never been before.