Papilio Polyxenses on Tanzania stamp

Papilio polyxenes or Black Swallowtails are a fairly common but very pretty butterfly with a wingspan of about a 8 to 11 cm (3.1 to 4.3 in). The Black Swallowtail (Papilio polyxenes) also called the American Swallowtail or Parsnip Swallowtail, is a butterfly found throughout much of North America. They are easy to attract to host plants to lay eggs, and the caterpillars are easy to rise also.

The upper surface of the wings is mostly black. On the inner edge of hindwing is a black spot centered in larger orange spot. A male of this species has a yellow band near edge of wings; a female has row of yellow spots. The hindwing of the female has an iridescent blue band. It is the state butterfly of Oklahoma. The Black Swallowtail caterpillar has an orange "forked gland", called the osmeterium. When in danger the osmeterium, which looks like a snake's tongue, everts and releases a foul smell to repel predators.