The monarch butterfly is one of the best-known and most easily recognizable butterflies on Earth. It has orange wings outlined with black lines and white dots. The orange wings are crisscrossed with black veins. Monarch butterflies are famous for their winter migration from the northern United States and Canada south to California and Mexico.
Monarch butterflies are native to North and South America. They belong to a class of mostly tropical and subtropical butterflies known as milkweed butterflies. They thrive wherever milkweed and related plants grow.
Monarchs in North America are divided into two groups–those that breed west of the Rocky Mountains in summer and overwinter in southern California, and those that breed in the Great Plains and Canada in summer and overwinter in Central America. There are also populations in Hawaii, Portugal and Spain, and Australia, New Zealand, and elsewhere in Oceania.
Female monarch butterflies lay their eggs on the leaves of milkweed plants. A female usually lays between 300 and 500 eggs over a two- to five-week period. After a few days, the eggs hatch into larvae (caterpillars) and feed on milkweed plant leaves. Monarch larvae eat only milkweed.
After about two weeks the larvae spin protective cases around themselves (called chrysalis) and enter the pupa stage. During the pupa stage, the caterpillar changes into a fully-formed black-and-orange adult butterfly. Monarchs that emerge in spring or early summer will produce new young within a few days. Those that emerge in late summer or fall, almost immediately migrate south to warmer weather. Some monarch butterflies fly as many as 3,000 miles during migration.
During their migration and often during winter, Monarchs will huddle by the thousands on trees to stay warm and await good weather. Monarchs migrating north in spring and early summer often stop along the way to lay eggs. The new generation will then continue north. It can take four or five generations for Monarchs to fly from Mexico to Canada in spring. Once Monarchs reach their destination they disperse for the summer and will not reunite as a group until the next migration. Monarchs use the sun to guide their journey; they also have an internal magnetic compass that allows them to fly on cloudy days.
Monarchs, like other butterflies, attract predatory birds. But the milkweed plants Monarchs feed on contain a toxin that is foul-tasting and poisonous to birds. Monarchs can store the toxins and have evolved to tolerate them. The Monarch’s bright colorful pattern has become a “do not eat” warning to birds.
The Monarch butterfly has a wingspan of 3.7 to 4.1 inches (9.3-10.4 cm) and weighs 0.0095 to 0.026 ounces (.76 g). A Monarch butterfly can live six to eight months. The scientific name of the Monarch butterfly is Danaus plexippus.