Every fall, millions of monarch butterflies begin an amazing trip. These orange-and-black butterflies live in many parts of the United States and Canada during warm months. When days grow shorter and air turns cooler, monarchs travel south.

Some monarchs fly more than 2,000 miles to mountain forests in Mexico. Others from the western United States spend winter along the California coast. A monarch weighs less than a paper clip, yet it can glide for hours by using warm air currents and favorable winds. The butterfly also seems to use the sun like a kind of map.

One special fact about monarch migration is that not every butterfly makes the whole round trip. In spring and summer, monarchs lay eggs on milkweed plants. The eggs hatch into caterpillars, which later change into butterflies. These new butterflies keep the journey going. It may take several generations to travel north again.

The butterflies that fly south in fall are different. They live longer than summer monarchs and can survive the whole winter. Scientists sometimes call them the "super generation."

Monarchs need safe places to rest and plenty of milkweed for their young. When people plant milkweed and protect forests, they help these travelers continue one of nature's most remarkable migrations.