Monarch Butteerly Migration
Monarch butterflies duriing migration. Photo by Gene Neiminen, USFWS
Monarchs on migration. Photo by Gene Nei

The monarch butterfly, easily recognized by its dark orange wings and black veins, is one of few butterflies that migrates. As the days grow shorter, the fall migration begins and millions of monarchs make their way south. From September to the third week of October monarchs in central and eastern U.S. make their way south to overwinter in the Gulf States and remote mountain valleys of south central Mexico.

Peninsulas are good areas to observe migrating butterflies. In the Chesapeake Bay area, Point Lookout, Eastern Neck National Wildlife Refuge and Black Walnut Point in Maryland and Cape Charles and Kiptopeke in Virginia often attract monarchs. Migrating monarchs often rest at these and other southern tips before crossing water.

By November they have usually reached their winter destinations, sometimes two thousand miles away. They will spend the next five months overwintering in a dormant state, massed on the trees in the Gulf States and Mexico. One wintering site may attract millions of butterflies.

Monarch butterfly on butterfly weed. Photo by Randy Loftus, USFWS
Monarch butterfly on butteerfly weed. Photo by Randy Loftus, USFWS

In March, as temperatures begin to rise, monarchs become active again. They mate and the butterflies, mostly females, begin to return north. This migration is not as spectacular as the fall migration. It is a long drawn out effort and butterflies usually do not congregate.

By May or June most monarchs have returned to North America. Here their journey ends. The females lay their green eggs on milkweed plants and then die. About one week later the eggs break open to reveal a yellow, black, and white striped caterpillar. Monarch caterpillars feed exclusively upon milkweeds.
 The monarch caterpillar molts five times until it is about two inches long. Then it attaches to a plant or other object by a silk thread. After one day, the caterpillar skin splits open and the pupa, or chrysalis, form emerges. The pupa is shiny green with gold spots and a black and gold band. The caterpillar remains in the pupal case, undergoing the final metamorphosis.

Six weeks after eggs were laid, the adult butterfly breaks out. This mature butterfly will complete the journey north, instinctively flying to a place it has never seen before. These adult butterflies may mate and establish another brood. As autumn approaches, the cycle continues as this new generation of monarchs migrates south.

Due to migratory nature, monarch butterflies need food and habitat in their northern summer homes, along their fall and spring migratory paths, and in the specific forest areas in countries and states of the of the Gulf of Mexico.

Roads, commercial development, homes and farms can destroy important monarch habitat. Milkweed, their host plant is considered a weed by some people and is often destroyed. Many monarchs and other butterflies are killed by pesticides. Simple steps like planting milkweed and other important wildflowers and reducing herbicide and pesticide use helps monarchs.

Monarchs are even more vulnerable at their winter sites. Eastern monarchs that migrate to the Mexico, roost in trees which are valuable for lumber. Conservation organizations are working with agencies and local groups to protect land, and educate the public about monarch conservation. For more information about conserving monarch butterflies contact:
Monarch Watch

Monarch Butterfly Sanctuary Foundation