Black swallowtails become familiar to gardeners because their caterpillars feed on plants in the carrot-parsley-dill family. They are one of several black or blackish swallowtails common in Missouri:
- From below, black swallowtails can be separated from pipevine swallowtails 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.
The caterpillars change greatly as they develop:
- Mature larvae are green with orange-spotted black bands.
- Younger larvae are mostly black with orange spots and usually have a whitish band or saddle across the middle; they often have tiny spikes.
- When disturbed, the caterpillars rear back, and a stinky, orange, forked gland (called an osmeterium) pops out to deter predators. The gland looks like horns or a forked tongue on the back of the caterpillar’s head.
Similar species: The virtually identical Ozark swallowtail, or Missouri woodland swallowtail (Papilio joanae) lives in scattered colonies throughout the Ozarks, confined to wooded habitats and glades in that region (while black swallowtails are usually seen in more open, sunny habitats). For more information about this rare species, see the Ecosystem Connections section.
Wingspan: 2¾–4 inches.
Statewide.
Habitat and Conservation
Mainly found in open habitats, including grasslands and old fields, along roadsides, and in gardens, backyards, and parks.
The flight is fast and dashing, a few feet above the ground.
Food
Larvae feed on virtually any plant in the carrot family, including cultivated dill, fennel, carrots, parsnips, parsley, and celery.
They also eat wild-growing Queen Anne’s lace, sweet cicely and anise root, prairie parsley, golden Alexanders, meadow parsnip, and even the deadly poisonous water hemlock and poison hemlock.
The adults visit a great variety of flowers for nectar and are often found taking moisture from wet ground.
Status
Common breeding resident.
Life Cycle
Adults fly from April through late fall.
As with most other butterflies, females lay eggs on suitable food plants and the larvae hatch, eat, grow, and molt. Mature larvae seek sturdy upright structures upon which to form the chrysalis. The chrysalis can be tan or greenish and is usually adhered to the surface at the “foot,” and secured midway with a slinglike strand of silk.
This species overwinters in the chrysalis stage.
Human Connections
The larvae eat several common garden plants, including parsley, fennel, dill, and carrots. If the plants are few and small, the caterpillars can damage the harvest — but most of us don’t mind trading some parsley for a crop of swallowtails and the chance to see the miracle of metamorphosis!
Although the caterpillars of this common butterfly often eat plants of importance to humans, the eggs are laid singly. These caterpillars rarely cause serious damage.
Many people have witnessed this butterfly’s life cycle in elementary school.
Ecosystem Connections
The caterpillars are herbivores that graze on vegetation. The adults serve a role in pollination.
Because it resembles the toxic pipevine swallowtail, this species gains protection from predators, whether it is itself toxic or not. When the caterpillars grow up eating deadly toxic water or poison hemlocks, this species likely becomes toxic itself.
Relatives: The Ozark swallowtail, or Missouri woodland swallowtail (Papilio joanae) is confined to wooded habitats and glades in the Ozarks. Its coloration is virtually identical to that of the black swallowtail.
- It is rare and, except for some populations in Arkansas, occurs entirely within the Missouri Ozarks region.
- It is a Missouri species of conservation concern, ranked as imperiled to critically imperiled.
- It looks so much like the black swallowtail it was once thought to be a variant of it. Behavior is one way it's different.
- From below, the hindwing orange spots show very little yellow.
- From above, the black dot in the center of the orange eyespot usually touches the outer edge of the wing.
- The caterpillars eat similar food plants, such as wild-growing meadow parsnip, yellow pimpernel, and golden Alexanders.
- Adults are fond of rose verbena, wood betony, puccoon, and false garlic.
- Males perch on trees and shrubs in small clearings at high points in the woodlands, watching for females.
- The Ozark swallowtail was discovered by Missouri lepidopterist J. Richard Heitzman in 1973, who named it P. joanae for his wife and partner lepidopterist, Joan E. Heitzman.
- DNA analysis has shown that it's more closely related to the Old World swallowtail (Papilio machaon) than to the lookalike black swallowtail. The Old World swallowtail occurs in Eurasia and western North America, but not in Missouri.
- Researchers suspect that the Ozark swallowtail originated as a population of Old World swallowtails that were geographically isolated during the times of glaciers. Once separated from the rest, they evolved independently to become the Ozark swallowtail.
