The Black Swallowtail, one of North America’s most common butterflies, frequently visits backyard gardens. Nicknamed parsley worms, the caterpillars feed on parsley, dill, fennel, and other members of the carrot family.
This large butterfly has black wings with yellow markings and a wingspan of 8-11 cm. The male displays a row of bold yellow spots, while the female’s spots are faded shades of yellow and blue. The Black Swallowtail’s colors mimic those of other similar species, such as the Giant or Pipevine Swallowtails. To identify the Black Swallowtail, look for a pair of black dots centered in larger orange circles on the inner edge of the hind wings.
The Black Swallowtail caterpillar changes appearance each time it molts. In the last few stages of growth, it is white and green, with black bands and yellow or orange spots.
Butterflies feed on nectar from flowers. Caterpillars feed on plants in the carrot family, which includes dill, fennel, parsley, and carrots.
Like all butterflies, the Black Swallowtail undergoes a complete metamorphosis. The life cycle has four stages: egg, larva, pupa, and adult.
Egg - It takes 3-5 days for eggs to hatch.
Larva - The caterpillar has five instars.
Pupa - The chrysalis stage lasts 9-11 days, or over winter.
Adult – Northern areas have 1-2 generations; southern areas may have three.
Special Adaptations and Defenses:
The caterpillar has a special gland called an osmeterium that emits a foul odor when the caterpillar is threatened. The orange osmeterium looks like a forked snake tongue. Caterpillars also ingest oils from the host plants of the carrot family; the foul taste of the chemical in their bodies repels birds and other predators. The chrysalides of the Black Swallowtail can be green or brown, depending on the color of the surface to which they are attached. This form of camouflage keeps them hidden from predators. The adult butterfly is thought to mimic the Pipevine Swallowtail, which is distasteful to predators.
Open fields and meadows, suburban yards, and roadsides.
Most of North America east of the Rocky Mountains, spreading south all the way to the northern tip of South America. Also present in Australia.
Other Common Names:
Eastern Black Swallowtail, Parsley Worm, Parsnip Swallowtail