Insect belonging, like moths, to the order Lepidoptera, in which the wings are covered with tiny scales, often brightly coloured. There are some 15,000 species of butterfly, many of which are under threat throughout the world because of the destruction of habitat.

Butterflies have a tubular proboscis through which they suck up nectar, or, in some species, carrion, dung, or urine. Metamorphosis is complete; the pupa, or chrysalis, is usually without the protection of a cocoon. Adult lifespan may be only a few weeks, but some species hibernate and lay eggs in the spring.

The largest family, Nymphalidae, has some 6,000 species; it includes the peacock, tortoiseshells, and fritillaries. The family Pieridae includes the cabbage white, one of the few butterflies injurious to crops. The Lycaenidae are chiefly small, often with metallic coloration, for example the blues, coppers, and hairstreaks. The large blue Lycaena arion has a complex life history: it lays its eggs on wild thyme, and the caterpillars are then taken by Myrmica ants to their nests. The ants milk their honey glands, while the caterpillars feed on the ant larvae. In the spring, the caterpillars finally pupate and emerge as butterflies. The mainly tropical Papilionidae, or swallowtails, are large and very beautiful, especially the South American species. The world's largest butterfly is Queen Alexandra's birdwing Ornithoptera alexandrae of Papua New Guinea, with a body 7.5 cm/3 in long and a wingspan of 25 cm/10 in. The most spectacular migrant is the orange and black monarch butterfly Danaus plexippus, which may fly from northern Canada to Mexico in the autumn.

Butterflies usually differ from moths in having the antennae club-shaped rather than plumed or feathery, no 'lock' between the fore- and hindwing, and resting with the wings in the vertical position rather than flat or sloping.