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Wednesday, September 27, 2006

Migration of the Monarch

In the Blue Ridge Mountains of Virginia, where I live, monarch butterflies (Danaus plexippus) made their first appearance on their migration south about a week ago. There are many butterfly bushes in my gardens that are still blooming and they have been covered in monarchs all week.

Eastern populations of the monarch winter in Florida, along the coast of Texas, and in Mexico, and return to the north in spring. Monarch butterflies follow the same migration patterns every year. During migration, huge numbers of butterflies can be seen gathered together.

Milkweed is the chosen plant of the monarch; actually, the monarch butterfly is sometimes called the "milkweed butterfly" because its larvae eat the plant. In fact, milkweed is the only thing the larvae can eat! If you'd like to attract monarchs to your garden, you can try planting milkweed.

Most predators have learned that the monarch butterfly makes for a poisonous snack. The toxins from the monarch's milkweed diet have given the butterfly this defense. In either the caterpillar or butterfly stage the monarch needs no camouflage because it takes in toxins from the milkweed and is poisonous to predators. Many animals advertise their poisonous nature with bright the vein of the monarch!

Unlike most other insects in temperate climates, monarch butterflies cannot survive a long cold winter. Instead, they spend the winter in roosting spots. Monarchs west of the Rocky Mountains travel to small groves of trees along the California coast. Those east of the Rocky Mountains fly farther south to the forests high in the mountains of Mexico. The monarch's migration is driven by seasonal changes. Day-length and temperature changes influence the movement of the monarch.

In the entire world, no butterflies migrate like the monarchs of North America. They travel much farther than all other tropical butterflies, up to three thousand miles. They are the only butterflies to make such a long, two way migration every year. Amazingly, they fly in masses to the same winter roosts, often to the exact same trees. Their migration is more the type we expect from birds or whales. However, unlike birds and whales, individuals only make the round-trip once. It is their children's grandchildren that return south the following fall.

Some other species of Lepidoptera (butterflies and moths) travel long distances, but they generally go in one direction only, often following food. This one-way movement is properly called emigration. In tropical lands, butterflies do migrate back and forth as the seasons change. At the beginning of the dry season, the food plants shrivel and the butterflies leave to find a moister climate. When the rains arrive, the food plants grow back and the butterflies return.

If you live south of Virginia and have been waiting for the monarchs to pass through your area, keep looking, because if they have not already reached you they will soon.

If you would like to know more about monarch butterflies visit, Monarch

If you would like to learn how you can attract monarch butterflies to your area and in doing so help insure that they can make the arduous migration visit the, Monarch Waystation Program. Monarchs need our help! Get involved in monarch conservation by creating a Monarch Waystation.

Images by D L Ennis



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