The Old World Swallowtail (Papilio machaon), is a butterfly of the family Papilionidae. The butterfly is also known as the Common Yellow Swallowtail or, simply, The Swallowtail (a common name applied to all members of the family). It is the type species of the genus Papilio and occurs throughout the Palearctic region in Europe and Asia; it also occurs across North America, and thus, is not restricted to the Old World, despite the common name.
This striking butterfly is yellow with black wing and vein markings and a wingspan of 8 to 10 cm. The hind wings of both sexes have a pair of protruding tails which give the butterfly its common name from the resemblance to the birds of the same name. Just below each tail is a red eye spot.
This butterfly is present throughout the entire Palearctic region, ranging from Russia to China and Japan, (including the Himalayas and Taiwan), and across into Alaska, Canada, and the United States. In Asia it is reported as far south as Saudi Arabia, Oman, the high mountains of Yemen, and Israel as well.
In Southern Asia it occurs in Pakistan and Kashmir, Northern India, (Sikkim, to Assam and Arunachal Pradesh) Nepal, Bhutan, and northern Myanmar.
This butterfly is widespread in Europe. In the United Kingdom it is limited to a few areas in the Norfolk Broads of East Anglia. It is the UK's largest resident butterfly. The Monarch Danaus plexippus is slightly larger, but is only a rare vagrant.