Butterflies eat by sipping nectar and other liquids through their proboscis, a tubular appendage that functions like a straw. The larvae of butterflies, called caterpillars, feed voraciously on plant material, especially leaves.
The diet of adult butterflies consists entirely of liquids. Most butterflies draw nourishment from the nectar of flowers, which supplies sugar, sodium and other minerals. Sometimes, butterflies supplement their sodium intake by lighting on humans and ingesting sweat. Some species of butterflies do not visit flowers, but instead ingest sap from trees, the liquid from rotting fruit, and moisture from wet dirt and sand. Other species derive nourishment from the decaying flesh of rotting animal carcasses. Butterflies use sensory organs called sensillae located on their antennae for smell and chemoreceptors on their feet for taste.
Butterfly larvae spend almost all their time eating and searching for food. They mainly eat leaves, but some species also eat flowers, seeds, seed pods, aphids and other insects. Many species of butterfly larvae prefer particular types of plants. Pearl crescent caterpillars, for instance, eat mainly asters. Caterpillars grow rapidly, shedding their skins several times as they mature. Every time they molt, their appearance changes. When they have ingested sufficient nutrition and are ready for metamorphosis, they find a suitable location, such as the underside of a leaf, and transform into pupae. During this phase, they do not feed until they transform into adult butterflies.