Life History: Adults warm up by basking dorsally (with their wings open and toward the sun). Females lay eggs singly under the host leaves; caterpillars eat leaves and flowers. Adults make massive migrations from August-October, flying thousands of miles south to hibernate along the California coast and in central Mexico. A few overwinter along the Gulf coast or south Atlantic coast. Along the way, Monarchs stop to feed on flower nectar and to roost together at night. At the Mexico wintering sites, butterflies roost in trees and form huge aggregations that may have millions of individuals. During the winter the butterflies may take moisture and flower nectar during warm days. Most have mated before they leave for the north in the spring, and females lay eggs along the way. Residents of tropical areas do not migrate but appear to make altitude changes during the dry season.