Papilio machaon, the Old World swallowtail, is a butterfly of the family Papilionidae. It is also known as the common yellow swallowtail or simply the swallowtail. It is the type species of the genus Papilio. This widespread species occurs throughout much of the Palearctic region. The species is named after Machaon, a figure in Greek mythology and a son of Asclepius mentioned in the works of Homer. The larva initially resembles a bird dropping, which serves as an effective camouflage against predators. As it grows, the caterpillar becomes green with black and orange markings.