The peacock butterfly (Aglais io) is a strikingly colored butterfly found throughout much of Europe and temperate Asia, easily recognized by its rich reddish-brown wings, each marked with a large, vivid eyespot on the fore- and hindwings that resemble the "eyes" on a peacock's tail feathers, giving the species its common name. These eyespots serve as a startle defense, since the undersides of the wings are dark and cryptic, camouflaging the resting butterfly among leaf litter or bark, but when disturbed it can suddenly flash its wings open to reveal the bright, eye-like patterns and even produce a hissing sound to deter predators. Peacock butterflies are commonly seen in gardens, meadows, woodland edges, and parks, where adults feed on nectar from a wide range of flowers, and they are one of the most familiar and widespread butterflies across their range. The caterpillars are black, spiny, and gregarious, feeding communally primarily on stinging nettles, and the species typically produces one or two generations per year, with adults overwintering in sheltered spots such as tree hollows, sheds, or buildings before emerging in spring to mate and lay eggs.