From below, black swallowtails can be separated from pipevine and dark female eastern tiger swallowtails by the two rows of red-orange spots. They are separated from spicebush swallowtails by the complete row of spots in the middle area: There are no “missing” spots, and there is a small spot just to the basal (inner) side of the median row.
Seen from above, both sexes have two rows of yellow spots; these spot bands are generally wider on males. A small yellow spot is present toward the tip of the forewing; spicebush swallowtails lack this spot. As mimics of the distasteful pipevine swallowtail, females have blue scales on the top of the hindwing.
Larvae change greatly as they develop. Mature larvae are green with orange-spotted black bands. When disturbed, they rear back and evert an osmeterium, a stinky, orange, forked gland that deters predators. Younger larvae are mostly black with orange spots and usually have a whitish band or saddle across the middle; they often have tiny spikes.