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Monarch Butterfly

Natural History

Monarch Butterflies are a large orange and black butterflies with wingspans of 3 - 4.5 inches. They are sometimes referred to as 'milkweed' butterflies, since the larvae feed exclusively on this plant. Adult female monarchs lay their eggs on the underside of milkweed leaves in the spring. These eggs typical hatch in three to twelve days producing a larvae which feed on the milkweed leaves for about two weeks and develop into yellow, black and white striped, two inch long caterpillars. The milkweed contains a poison that makes the monarchs taste bad to birds and other predators, which soon learn to avoid them. Caterpillars eventually form a shiny green and gold speckled chrysalis. The adult monarch emerges from the chrysalis about two weeks later.

Tagged monarchs have been documented as flying as much as an 1870 mile long migration route (point to point distance, which doesn't take into account that fact that butterflies don't fly in a straight line).

As the weather becomes colder, millions of monarchs begin their annual migration south to fir forests in the mountains of central Mexico where they spend the winter. Other monarchs will migrate west to the central and southern California coast. In the spring the monarchs make the long flight back north and lay eggs along the way. When the eggs hatch into caterpillars, the whole cycle begins once more.


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