Butterfly

Monarch butterflies are known for the incredible mass migration that brings millions of them to California and Mexico each winter. North American monarchs are the only butterflies that make such a massive journey—up to 3,000 miles (4,828 kilometers). The insects must begin this journey each fall ahead of cold weather, which will kill them if they tarry too long.

Monarch butterflies begin life as eggs and hatch as larvae that eat their eggshells and, subsequently, the milkweed plants on which they were placed. (Monarchs are dependent on milkweed plants, which larvae eat nearly exclusively.)

Fattening larvae become juicy, colorful caterpillars, then create a hard protective case around themselves as they enter the pupa stage. They emerge as beautifully colored, black-orange-and-white adults. The colorful pattern makes monarchs easy to identify—and that's the idea. The distinctive pattern warns predators that the insects are foul tasting and poisonous.

Butterflies that emerge fro