The Life Cycle of the Black Swallowtail

Egg

• Black swallowtail eggs are nearly white and round. Butterflies lay their eggs on a host plant that will become food for the caterpillars when they hatch in 3 to 5 days. The black swallowtail's common host plants are in the carrot family: carrot, Queen Anne's lace, dill, fennel and parsley.

Larva

• The egg hatches into a tiny caterpillar, about 2mm long. It immediately eats any egg remains, then begins feeding on the host plant. As the caterpillar grows it molts (sheds skin) several times. Each time the caterpillar molts it begins a new stage with a different appearance. Each stage between molts is called an "instar." Stages are the first instar, second instar, advancing until the final fifth instar. The Papilio polyxenes larva begins as a tiny black caterpillar with a white band around its middle, and it progresses through instars until it is the large green, yellow, white and black caterpillar pictured.

Pupa

• The fifth instar is the full grown larva. When it is ready to pupate, it defecates a final time, and in this cleansed state it crawls off to find a sheltered spot. Black swallowtails generally attach to sticks or stems to pupate. The last pair of feet remains attached to the stick, and they spin a web of silk around their head, connecting them to the stick in a "C" shape. The final molt occurs within 24 hours; the shed skin becomes part of the chrysalis.

  The black swallowtail chrysalis is usually dark brown and looks something like a folded up dry leaf. It may also be light brown with yellow, or even green and yellow.

Adult

• The adult butterfly emerges after 9 to 11 days, or longer if temperatures are cool or if the pupa overwinters. The adult climbs to an open area and begins pumping its small wings immediately. This action pushes fluids from the abdomen through the veins of the wings, causing them to enlarge to full size. The action also dries the wings and exercises muscles needed for flying.

  The female has more blue than the male, and the male has more yellow than the female.

Butterfly Garden

• Attract black swallowtails to your garden by growing nectar flowers for adult butterflies to feed from and the host plants they need to lay eggs. Butterflies also need shelter to roost at night, which can be a simple undisturbed shrubby area of your yard or garden or a wooden butterfly house.

  Water is vital; shallow water is ideal. Swallowtails like to "puddle," an activity where they gather at shallow water and sip in minerals they cannot get from nectar.