Raising Black Swallowtail Butterflies
Metamorphosis of Papilio polyxenes as a Summer Project for Kids
A good choice for beginning butterfly farmers, Papilio polyxenes is easy to attract, feeds on more than one species of host plant, and you can watch the entire life cycle in as little as two weeks.
Black Swallowtails are large and brightly colored, with a wingspan of roughly three to four inches, and a swirling, graceful flight. They are mostly black with males having a band of yellow at the edge of its wings, while females bear a row of yellow spots instead. Both have a blue area between the bands on the hinds wings, though on females, this is more pronounced. Deep orange eye spots grace the tail end of both sexes, no doubt a hoax for predators. Native to North America, they are found in most states except for the Pacific Northwest, Northern and Coastal California, and Idaho (Opler, Pavulaan, Stanford and Pogue, 2006).
Start by attracting the butterflies to your yard with nectar producing flowers they love, such as milkweed, pentas, coneflowers, or zinnias. Female butterflies lay eggs on specific host plants you will need to provide. Eggs are yellowish-white and laid singly on carrots, parsley, dill, fennel and Queen Anne's Lace.
Each molt of the caterpillar is marked by a growth phase known as an instar, with five instars typical of this species. After hatching, they are less than half an inch in length, barely visible at first glance. They are blackish-brown, with orange spikes and a central band of white, resembling bird droppings as they grow - a great defense against would-be predators. A horn-like projection called an osmetrium is another form of defense that appears from the head when disturbed, along with a foul odor emission.
By the fourth instar, spikes vanish and black and pale green stripes take their place. Fully grown, the caterpillar reaches about 2 inches in length and can make a dent in any garden with its voracious appetite.
Gardeners often hand-pick caterpillars and transfer them to a few sacrificial plants, sparing their garden and the butterflies. To raise them indoors, set up an aquarium with a few host plants – live if possible. It is imperative they have a constant source of fresh food - they will reject it an hour or two after picking.
Just before pupating, the caterpillar wanders from its food source to find a place to suspend its chrysalis. Be sure to provide sticks propped up in the tank to offer pupation sites. After clearing its intestine a final time, the caterpillar finds a suitable location and slowly attaches its head and last pair of legs with spun silk. After a final molt, the caterpillar transforms into either a brown or green chrysalis, blending with its surroundings.
The Swallowtail can spend as little as five days in the chrysalis, or as much as three or four months if it overwinters as a pupa. As emergence approaches, the chrysalis becomes more transparent, making the wings of the butterfly visible. When it emerges, the new butterfly will need to stay suspended upside down for a time as it pumps blood from its body into wrinkled wings not yet prepared for flight. This generally takes 1-2 hours, so take care not to release them before they are ready, as they are vulnerable to birds and other predators during this time.
Release them near the nectar plants you have in your yard to continue the life cycle!
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