Black swallowtail

Like all Lepidoptera, the black swallowtail undergoes complete metamorphosis. After mating, the female lays her eggs on the leaves of a host plant, which will provide food for the future caterpillar.

A few days later, a tiny caterpillar hatches. Black with a white patch on its back, it resembles bird droppings, an appearance that helps protect it from predators during the earliest stages of its life.

Over the course of four molts, the caterpillar changes dramatically. It grows larger and turns green, with yellow and black stripes, reaching about 5 cm in length.

When it is ready to become a chrysalis, the caterpillar attaches itself to a support such as a sturdy stem. It anchors the tip of its abdomen and spins a silk girdle to hold itself in place. Once everything is secure, the caterpillar’s cuticle splits open, revealing a green chrysalis.

The time it takes for the adult to emerge varies by region. In Canada, there are two generations each year. In the first generation, the chrysalis develops for about 9 to 15 days before the adult emerges. In the second, the chrysalis overwinters, and the adult emerges in spring.