The lepidopterans (butterflies and moths) are one of the largest of the insect orders, and are also the most popular group of insects from a human perspective.

Many species have large and colourful wings, and the wing patterns are produced by rows of tile-like flattened scales which cover the wing surface. The wing scales, which are modified hairs, are unique for the order, though scales as body cover has arisen in several insect orders. Another unique feature of the lepidopterans are the mouth parts, consisting of a long, flexible proboscis formed by the fused galea. In rest, the proboscis, which is used for sucking up nectar and other liquids, is held coiled up beneath the head. The most basal members of the order, the Micropterigidae, lack the proboscis and have functional mandibles which they use for chewing pollen grains. The Lepidoptera have complete metamorphosis, and the larvae are with few exceptions terrestrial herbivores. The pupa is obtect, and is often protected by a silken cocoon.