The butterfly's head is the location of its feeding and sensory structures. The proboscis uncoils to sip food, and coils up again into a spiral when not in use. The lepidopteran with the longest proboscis is the hawk moth. An optic nerve then carries this information to the insect's brain. Antennae are used for the sense of smell and balance.
Butterflies have two segmented antennae with a small club at the end of each.
Moths have antennae without the club. Johnston's organ is an organ located at the base of a butterfly's antennae. This organ are responsible for maintaining the butterfly's sense of balance and orientation, especially during flight. Palps are the mustache-like scaly mouthparts of adult butterflies that are on each side of the proboscis. These palps are covered with sensory hairs and scales, and test whether something is food or not.