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Insects and other arthropods

Black swallowtail

Papilio polyxenes asterius

Tabs group


This butterfly’s wingspan is between 9 and 10 cm. Its black wings have two rows of yellow spots along the edges. The lower wings have an orange spot with a black centre on the bottom edge, and the tip of the wing is long and thin.

Females can be distinguished from males by their larger abdomens and a wide band of blue scales on their back wings. The two rows of yellow spots are less pronounced in females.

Life cycle

In Canada, there are two generations of black swallowtails each year. After mating, the female lays her eggs on the leaf of a host plant. The female lays between 200 and 400 eggs at a time.

After a few days, a small caterpillar appears. The black caterpillar, with a saddle-shaped white spot on its back, looks like a bird dropping. The caterpillar moults four times. After a month, it is 5 cm long. Each segment of its body has a green stripe and a black stripe with yellow or orange dots.

Before it metamorphoses into a chrysalid, the caterpillar attaches itself to a stiff branch or rock. It spins a thin belt of silk to tie the upper part of its body to the branch or rock. Its cuticle splits open and the chrysalid emerges.

In first-generation butterflies, the chrysalis takes between 9 and 15 days before turning into an adult. For those of the second generation, the chrysalis overwinters and it is the following spring that the adult emerges.

Geographic distribution

Black swallowtails are found in North America east of the Rockies all the way to Florida and Mexico. The species is common in southern Ontario and Québec, but is also found in the Lower St. Lawrence, the Gaspé peninsula and the north coast of the Gulf of St. Lawrence.


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