Lepidoptera

Lepidoptera, the order that includes butterflies and moths, comprises roughly 180,000 described species, making it the second largest insect order after beetles. These winged insects are found on every continent except Antarctica, occupying habitats from deserts to rainforests, though they are almost always linked to flowering plants. The order contains 126 families and 46 superfamilies, representing about 8.6% of all described living organisms.

The name comes from Greek words for "scale" and "wing," coined by Carl Linnaeus in 1746. The English word "butterfly" may derive from the pale butter color of some species' wings, while "moth" traces back to Old English and Germanic roots. "Caterpillar" likely comes from Old North French, combining Latin for "cat" and "hairy."

Adult lepidopterans are distinguished by colored scales covering their bodies, large triangular wings (almost always membranous), and a proboscis for drinking nectar. Their antennae vary: butterflies typically have club-shaped antennae, skippers have hooked ones, and moths have variously enlarged or branched segments. The head also contains compound eyes and chaetosema, clusters of sensory bristles unique to this order, though some species lack one or both.

Caterpillars, the larval stage, have a hardened head capsule with chewing mouthparts called mandibles, used to consume plant matter. They possess a cylindrical body with three pairs of true legs and up to five pairs of prolegs. As they grow, they pass through stages called instars, changing appearance each time. Once mature, they become pupae. Many moths and a few butterflies spin a silk cocoon for protection before pupating; others go underground. Butterfly pupae, called chrysalises, have a hard skin without a cocoon. Inside the pupa, complete metamorphosis occurs, and a sexually mature adult emerges.

Mating and egg-laying typically happen near or on host plants for the larvae. Females often produce up to 600 eggs. As caterpillars, they are mostly herbivorous and can quickly consume large amounts of leaves, making them agricultural pests. As adults, they feed on nectar and serve as economically important pollinators.

Lepidopterans first appeared in the fossil record at the Triassic-Jurassic boundary and coevolved with flowering plants after the angiosperm boom in the Cretaceous. They have developed a wide range of wing patterns, from camouflaged moths to vivid butterfly displays. A specialist who studies them is called a lepidopterist.

The order is among the most successful insect groups. The Siberian Apollo (Parnassius arcticus) lives in the Arctic Circle in northeastern Yakutia, while Apollo species like Parnassius epaphus occur high in the Himalayas. Some species are commensal or parasitic: sloth moths (Bradipodicola hahneli and Cryptoses choloepi) live exclusively in sloth fur; two Tinea species breed on cattle horns; the larva of Zenodochium coccivorella is an internal parasite of Kermes scale insects. Others breed in owl pellets, bat caves, honeycombs, or diseased fruit.

As of 2007, roughly 174,250 lepidopteran species were described, with butterflies comprising about 17,950 and moths the rest. Most live in the tropics, but diversity is substantial on other continents. North America has over 700 butterfly species and over 11,000 moth species; Australia has about 400 butterflies and 14,000 moths. John Heppner estimated diversity by faunal region in 1991, using counts from literature and card indices at the Natural History Museum in London and the National Museum of Natural History in Washington.