This family contains species that are the largest butterflies in North America. Swallowtails get their name from the "tails" on the back edge of their wings that reminded people of the forked tails of Swallows. Adults swallowtails have black or black and yellow/white wings, sometimes with additional blue or red markings. All Michigan species have the tails on their hindwings, but some species in other parts of North America don't have them.
Swallowtail caterpillars are large and smooth, but they have an orange "horn" that is hidden under the skin of the thorax. They pop it up when they are threatened by predators, and it gives off repellent chemicals. Young caterpillars are black with white spots, and look like bird droppings. As they get older they change color, then they are often green but with black or yellow stripes, and several species have large spots that look like eyes.
Some species of swallowtails are mimics of others that have toxic compounds in their bodies.
There are over 550 species of swallowtails around the world. Most are tropical, only about 30 are found in the United States, and only 8 are in Michigan.
Adult swallowtails fly in open areas (fields, vacant lots, meadows, open forest, sides of streams) near their food plants, especially where there are abundant flowers.
Caterpillars are found on their food plants.
Like all Moths and Butterflies, this family has complete metamorphosis. See More Information on Butterflies and Moths for an explanation of this. In cold climates they spend the winter as pupa in a chrysalis (no cocoon).
These butterflies don't usually live more than a year. They often have two generations a year, with some adults emerging in the Spring, and then their offspring emerging as adults in Fall. This second generation only lives for a few months.
Adults are only active during the day. Caterpillars may be active day or night. They are all solitary animals. A few species occasionally migrate, but this is not common.
Like all butterflies, they mainly use scent and sight for communication. Males attract females with pheromones and special display flights. Females leave scent marks on plants where they've laid eggs, telling other female not to put their eggs there.
Swallowtail catepillars eat leaves and flowers of particular plans. One Michigan species only eats plants in the genus Aristolochia (Virginia Snakeroot, Dutchman's Pipe). Another prefers trembling aspen, another wild cherry. Several species eat plants in the carrot family.
Adult swallowtails sip nectar, but also mud and sometimes manure.
Many of these species defend themselves with toxic chemicals, or mimic species that do. The caterpillars all produce chemicals the repel ants. They also are camouflaged, especially when they are young. The eyespots may startle or confuse a predator.
Adult swallowtails are strong fliers, and hide in trees at night.
These butterflies don't have strong effects on humans one way or the other. Sometimes they are a garden pest, eating carrots and related plants but this is not common. One species in the south is sometimes a minor pest of orange and lemon trees.
One species in Michigan is considered threatened, it is the Pipe-vine Swallowtail, Battus philenor. It's existence is threatened in Michigan because its food plant has become rare. It is still common in other states. This species collects toxic chemicals from its food plant, and so birds won't eat it. Several other species are mimics of this species. If the toxic species disappears, the birds won't learn not to eat it, and the mimics won't get any protection from looking like it anymore.
This family includes the largest butterfly species in Michigan, the Giant Swallowtail, Papilio cresphontes. It can have a wingspan of 15 cm. The largest butterflies in the world are in this family too, they are called "birdwing butterflies" and live in Australia and Southeast Asia. The largest have wingspans of over 25 cm!