Large butterfly, with a wingspan of 3-4 inches.  As in all swallowtails, there are two little tails at the back of the wings.  Males (shown at left) have two rows of white to yellow spots edging the wings and isolated yellow spots at the top.  The hindwings have powdery blue patches between the yellow rows.  In females the white to yellow spots are much smaller and the blue patches much larger.  Both sexes have two yellow to orange spots with a black bull's-eye, which is a key character for identification.

The underside of the wings is similar in both sexes, with two rows of yellow white to yellow spots on the forewing, and two rows of orange spots below, with a row of blue between, and a row of yellow at the margin.

The caterpillar is a handsome creature, with bands of green and black, and yellow spots.  In younger caterpillars, the green is darker and the spots more orange.  The youngest caterpillars have a large white patch on top.  The caterpillars, like all swallowtail caterpillars, have a forked orange structure, called and osmeterium, which can be everted to startle would-be predators.  Caterpillars feed on a wide variety of carrot family plants, as well as rue and sometimes citrus family.  They have a variety of names, Parsley Worm, Dill Worm, Carrot Worm, Fennel Worm, Celery Worm, etc, depending on what they are eating  Plants in the carrot family contain a variety of toxins that make the caterpillars distasteful to predators.  The striking yellow and black pattern is a way of saying, "Leave me alone; I'm bad to eat."

Native to the eastern US from Florida north to southern Canada, westward to Minnesota, and, in the south, westward all the way to California. Adults of both sexes hang out in open areas such as fields, gardens and roadsides.

The female is a member of the blue and black swallowtail complex, members of which all resemble each other and are protected by resembling the poisonous members of the group.  Eastern Blacks can be distinguished from all of the others by the orange spots with black bulls-eyes on the hindwings.  The Pipevine Swallowtail differs in having only one row of orange spots beneath.  The Spicebush Swallowtail differs in that one of the orange spots on the underside is replaced with a pale blue comet.  The black form of the female Eastern Tiger Swallowtail differs in lacking the two rows of orange spots beneath.  The male Eastern Black is similar to the Giant Swallowtail, but that species has an extra band of yellow spots across the upper surface of the wings, and lacks the two rows of orange spots below.

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