Black Swallowtail

How to tell it apart

• Black wings with two rows of yellow spots — bold in males, faint in females
• Iridescent blue scaling across the hindwing, extensive in females
• An orange eyespot near the tail with a black pupil sitting centrally
• Wingspan 70–100 mm, with a tail on each hindwing
• Caterpillar green with black bands and yellow dots, on parsley, dill or fennel

Where you’ll find it

The eastern and central United States, west to the Rockies.

Gardens, meadows, roadsides and allotments — anywhere in the carrot family grows.

Spring through autumn in two or three broods.

How it behaves

Females are darker and bluer than males, and that is not decoration: they resemble the pipevine swallowtail, which is genuinely toxic, and gain protection from the resemblance. The caterpillar goes through a complete change of strategy partway through its life, starting as a black-and-white bird-dropping mimic and finishing as the familiar green-banded larva. Adults nectar widely and are strong, fast fliers.

You’ve found one indoors

If they are on your parsley, that is the deal — a few plants sacrificed gets you butterflies. Move caterpillars to a spare plant rather than destroying them if you need the herbs. They do no damage beyond the foliage they eat.

Common questions

Commonly confused with

• Pipevine Swallowtail Harmless

Keep identifying

Identify another animal from a photo or return to the Butterflies guide.

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