Monarch Butterfly, most common species of the milkweed butterflies, so named because their larvae feed on milkweed plants. Found primarily in North America, the adult monarch has wings of a striking reddish-brown, with black veins and black borders with two rows of white dots. The wingspread may reach 10 cm (4 in).
Monarch butterflies are known for their long migrations.
Each autumn the adult monarchs that live east of the Rocky Mountains in North America migrate to central Mexico; adult monarchs west of the Rockies migrate to the California coast. The longest flight known for a tagged adult is some 2,900 km (some 1,800 mi) from Ontario, Canada, to Mexico. Migratory groups congregate at the same places each winter, such as Pacific Grove, California, or the mountains in central Mexico, where the trees may be completely covered with monarchs.
As winter ends, monarchs begin to mate. In March they leave their winter homes, flying north and east. On the northward journey, females stop to lay eggs on the underside of milkweed plants and die shortly thereafter. The offspring continue to migrate, returning to the same North American regions where their parents lived.
When monarch larvae feed on milkweed plants, they accumulate a poisonous substance in their bodies that makes them distasteful to birds and other predators. The birds learn to recognize the butterflies' bright pattern and avoid them. The viceroy butterfly shares similar markings to warn predators that it is unpalatable.
