This is a Monarch butterfly. Butterflies and
moths belong to the order Lepidoptera. Monarchs depend on milkweeds because they
are the only plants that monarch caterpillars can eat. The adult butterflies drink the nectar
of flowers. The monarch butterfly contains milkweed poisons that it ate when it was still
a caterpillar. The monarch is the only butterfly that migrates
for very long distances like some birds do. During the fall migration, sugars from nectar
are stored as fat in the butterflyís abdomen. This fat is necessary fuel for the butterflies
to complete their migration and overwinter successfully.
In the late summer and early fall of each year, shorter days and cooler temperatures
tell the monarch butterflies not to breed, but instead, to begin their long migration.
The monarchs that emerge in September and early October are the migrants. They will
live six to eight months. Because they are the great-grandchildren of the butterflies
that flew north the previous spring, they have never been to the overwintering sites
in California or Central Mexico. And yet somehow, they find their wayóprobably through an inherited
behavior pattern. The monarchsí overwintering sites in the
forests of the mountain ranges in Central Mexico are about 10,000 feet, or 3,000 meters,
above sea level. The tall trees make a thick canopy, helping to protect the monarchs from
wind, snow, rain, or hail. Fog and clouds settle on the trees and provide moisture.
To conserve energy, the butterflies cluster on trees where the temperature is just above
freezing. They cover whole tree trunks and branches. Hundreds of millions of butterflies
can overwinter in Mexico in one year. On the forest floor, the butterflies find
nectar sources among the flowering plants. On sunny days, the butterflies often warm
up enough to fly to nearby creeks and puddles where they drink water.
Monarchs begin mating as the weather warms in the spring. By early March they fly back
north in masses. The females must find early sprouts of milkweed on which to lay their