Monarch caterpillar with agency logo

Monarch caterpillar on milkweed plant with USFWS logo. 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.