By Kelly Slingerland

The swallowtails are members of the family Papilionidae, which are in the phylum Arthropoda and the class Insecta. They are a relatively small yet well known group of butterflies. They are prominent in nearly every part of the world and differ enormously in size. Some are among the largest of butterflies while others grow to a mere two inches.

Among the Papilionidae is the species of Papilio cresophontes, the Giant Swallowtail. Swallowtail caterpillars, which are commonly referred to as "Orange Dogs", are dark brown with creamy white markings. They have a yellow or orange groove between the head and the thorax. This Y-shaped organ is called the osmeterium and is used as a defense mechanism. When predators, such as birds, pose a threat to the caterpillar, it protrudes its osmeterium and releases a powerful, repulsive scent. Also, the swallowtail caterpillar’s thorax is quite swollen and the true head is tucked down below it so that a bird is likely to delay long enough for the scent mechanism to come into play. These larvae feed on various citrus trees including the prickly ash, the hop tree and the gas plant.

The pupae of swallowtails resemble green leaves or irregular pieces of twig or bark. They are suspended by silk that passes around the thorax and also by the end of their abdomen, where a structure called the cremaster is encased in a tightly attached button of silk. Like a great majority of butterfly pupae, a cocoon does not cover them.

Adult Giant Swallowtail butterflies grow to be about four and a half to five and a half inches in width and four to five inches in length. The body of the butterfly is yellow with a dark brown head and a dark brown dorsal surface of the thorax. The upper and lower wings are dark brown with a yellow stripe down the middle of each. Yellow spots run down the edges of each wing with red and blue spots near the tails of the lower wings. The ventral sides of the wings are basically yellow with brown accents. These butterflies can be found easily in Massachusetts, New York, Ohio, Michigan, and Minnesota, south to Key West and the Mexican border. In the north they are rare and sporadic. They like to live in many habitats including rocky and sandy hillsides near streams or gullies in the north and pine flats, towns, and citrus groves in the south. Swallowtails gather in great numbers on damp spots to satisfy their strong need for water and rise in swirling clouds when disturbed.

Written fall 2000, as a service learning project for Dr. Gary Coté's Biology 102 class at Radford University. Copyright Pathways for Radford.