A fema le monarch landed on a milkweed plant. Then she laid some eggs. She laid them on the underside of the leaves to protect them from potential predators and dangerous weather. When the eggs hatch, caterpillars emerge. They eat their eggshell for food first. Then they depend on milkweed to keep them alive. monarch caterpillars only eat milkweed. Most monarch caterpillars begin their chrysalis stage on the milkweed plant or very close to it. After about a day after emerging from the chrysalis, monarchs begin to fly around to gather nectar.