Most moths and nearly all butterfly caterpillars eat the leaves and flowers of plants. Some moth caterpillars eat fruit, or seeds, and a few eat animal foods like beeswax or fur. A very few species of caterpillars are carnivores, eating Aphididae or other soft-bodied Insecta.

Adults mostly drink nectar or sap. They sometimes feed on mud to get minerals, or on animal dung to get protein that they need.