Its wing span can reach 4 inches. Full grown parselyworms or caterpillars can reach 2 inches in length and are smooth and green, marked with black bands and yellow spots. Caterpillars feed on pipevines, Dutchman s-pipe and Virginia snakeroot. Adults emerge in the spring and seek host plants. Females lay round, yellow to cream colored eggs on the leaves.
Caterpillars hatching from eggs are initially black with a white saddle.
After molting several times, each larvae transforms into a pale green chrysalis that is suspended from a plant stem by a thread. Caterpillars have chewing mouthparts. Adults have siphoning mouths. This caterpillar is bad tasting to birds and other predators because of toxins absorbed from the host plants. Like other larvae of swallowtail butterflies, parselyworms have a defensive structure, called an osmeterium , right behind the head.