In the fall, something strange happens. The Monarchs that emerge then have a much longer lifespan, which allows them to migrate. Monarchs east of the Rockies fly south to Mexico, while butterflies west of the Rockies fly south to Pacific Grove, California. Some of these butterflies travel 2,500 miles to reach their wintering trees. These fall Monarchs live up to eight months, long enough to last through the winter and return to their spring home, where they lay eggs and start the cycle again.