Papilio machaon, the Old World swallowtail, is a butterfly of the family Papilionidae. The butterfly is also known as the common yellow swallowtail or simply the swallowtail. It is the type species of the genus Papilio. This widespread species is found in much of the Palearctic (it is the only swallowtail in most of Europe) and in North America. This species is named after Machaon, a figure in Greek mythology. Like all butterflies, Old World swallowtails undergo metamorphosis. Young caterpillars look like bird droppings which is a good camouflage. In the last two of the four instars they are green with black transversal bands carrying 6 rows of reddish spots. To defend themselves the larvae can protrude an orange, fleshy, smelling fork behind their heads called osmeterium.
