Migration of the Monarch Butterfly

The monarch butterfly (Danaus plexippus) is a milkweed butterfly (subfamily Danainae) in the family Nymphalidae. It may be the most familiar North American butterfly. Its wings feature an easily recognizable orange and black pattern, with a wingspan of 8.9–10.2 cm (3½–4 in) (the viceroy butterfly is similar in color and pattern, but is markedly smaller and has an extra black stripe across the hind wing).

The eastern North American monarch population is notable for its multigenerational southward late-summer/autumnmigration from the United States and southern Canada to Mexico, covering thousands of miles. The western North American population of monarchs west of the Rocky Mountains most often migrate to sites in California but have been found in overwintering Mexico sites. Monarchs were transported to the international space station and were bred there.

Monarch butterflies are not able to survive the cold winters of most of the United States so they migrate south and west each autumn to escape the cold weather. The monarch migration usually starts in about October of each year, but can start earlier if the weather turns cold sooner than that.

The monarch butterflies will spend their winter hibernation in Mexico and some parts of Southern California where it is warm all year long. If the monarch lives in the Eastern states, usually east of the Rocky Mountains, it will migrate to Mexico and hibernate in oyamel fir trees. If the monarch butterfly lives west of the Rocky Mountains, then it will hibernate in and around Pacific Grove, California in eucalyptus trees. Monarch butterflies use the very same trees each and every year when they migrate, which seems odd because they aren’t the same butterflies that were there last year. Tmonarch butterfliesurth generation of monarch butterflies, so how do they know which trees are the right ones to hibernate in? Monarch butterflies are the only insect that migrates to a warmer climate that is 2,500 miles away each year.