The eastern tiger swallowtail is Missouri's only swallowtail with yellow and black stripes. Some females are yellow with black stripes, similar to males, but others are black with darker black stripes. Both female forms have blue scales on the dorsal (top) side of the hindwings. Dark-form females do not have two complete rows of orange spots on the lower side of the hindwing.
Larvae are bright green and have two large eyespots on the thorax behind the head. Like other swallowtail caterpillars, when disturbed, they rear back and evert an osmeterium, a stinky, orange, forked gland that deters predators.