Photo by J. R. Baker

Source with more pictures and more info: Spicebush Swallowtail | NC State Extension Publications

Spicebush swallowtails, Papilio troilus, are butterflies that have a conspicuous tail on each hind wing. The forewings and body are black. The forewings have a row of white spots near the outer margin and another small row on the margin. The hind wings are black with two orange spots, a row of spots that fade from white to pale blue and a conspicuous pale blue area. Females lay eggs singly on the underside of host leaves. The worms generally fold leaves together to form a shelter in which they live on a silk lining. Young caterpillars mimic bird dropping. Older caterpillars are green with lovely blue spots. They also have ferocious eyespots, probably to deter predators. These worms usually feed on sweet bay, spicebush, and sassafras. The prepupae assume an comma shape. The chrysalis has two anterior horns and is suspended from a twig by a narrow silk band. The chrysalides may be brown or green, but overwintering chrysalides are always brown. Several generations occur each year.

Image text: An older spicebush swallotail caterpillar on sassafras.

Image caption (from source): Mature spicebush swallotail caterpillars are brownish below.