Adult black swallowtails range in length from seven to nine cm, and can reach a wingspan of 11.5 cm. Older larva vary from green to yellow and most often each segment is crossed by a black band. Pupae of this species can vary from green and yellow, to brown and white, to a black form.
The upper surface of an adult is black with two rows of yellow spots. In females these yellow spots are narrow and lighter, or nonexistent. On the upper surface of the adults' hind wing, there are irridescent blue spots on males and an irridescent blue band on females. On the upperside of the hindwing there is a large red spot that has a black center towards the tail. Under the forewing there are yellow spots, and on the underside of the hindwing there are a row of orange-red spots, in front of blue caps, followed by black centered red spots towards the tail. (Douglas, 1986; Ehrlich, 1961; Neck, 1996; Scott, 1986)
The range of black swallowtails (also known as American swallowtails) extends from Southern Canada, through North America, and down to South America. Included in the South American range are the West Indies. In North America, black swallowtails are not commonly found west of the Rocky Mountains. (Ehrlich, 1961; Neck, 1996)
Black swallowtails tend to be found in open areas such as meadows, fields, parks, gardens, lowlands, marshes, and deserts. (Jackman, 1998)
To find a female black swallowtail, males alternately perch on the tops of hills and then patrol in flat areas. Males defend territories of about 70 square meters where they perch and patrol. Courtship lasts for about 45 seconds,and mating follows.
Females lay round, cream-colored eggs on the leaves of Umbelliferae plants. A female black swallowtail lays on average 200 - 440 eggs, 30 - 50 per day, starting at two days after emergence from the pupal stage. (Jackman, 1998; Scott, 1986)
Once eggs are fertilized and laid, there is no longer any parental care.
The nocturnal behavior of seeking a nightly sleeping perch occurs in several frenzied flights. Once the butterfly finds a good stalk or tip of an herbaceous plant, it will rest for a few minutes. When finally settled, it closes its wings and lowers its abdomen into the sleeping position where it will remain all night. In the morning the butterfly wakes up and positions itself again with its wings open, but this time it turns around to catch the morning light.
It has been discovered that black swallowtails mimic pipevine swallowtails, a distasteful species. By mimicking distasteful pipevine swallowtails, adult black swallowtails gain some protection where their ranges overlap. (Bordoni and Forestiero, 1998; Douglas, 1986; Scott, 1986)
The larvae of American swallowtails are attracted to the oils of plants such as dill, parsley, celery, carraway and carrots. These plants have adapted to insects herbivores by producing specific chemicals that repel the insects that try to eat them. American swallowtail larvae are resistant to these chemicals and make the caterpillar bad-tasting to bird predators. Some plants from the Umbelliferae family make psoralens that reduce growth rate and fertility in American swallowtails. The larva are most often found at small flowers. Adults feed on flower nectar and mud. (Douglas, 1986; Jackman, 1998; Neck, 1996; Scott, 1986)
These butterflies pollinate many plants. Their larvae eat many plant species. They also may provide food for many predator species.
The caterpillar of this species is occasionally a pest in gardens and farms. (Jackman, 1998)
These butterflies have no positive economic effect on humans.
These butterflies are widespread and do not seem to be threatened.
Matthew Wund (editor), University of Michigan-Ann Arbor.
Katy Eby (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.
Bordoni, S., Forestiero. 1998. Butterflies of the World. Ontario, Canada: Firefly Book.
Douglas, M. 1986. The Lives of Butterflies. Rexdale, Canada: The University of Michigan Press.
Ehrlich, P. 1961. How to Know Butterflies. Dubuque, Iowa: WM. C. Brown Company Publishers.
Jackman, 1998. A Field Guide to Common Texas Insects. Houston, Texas: Gulf Publishing.
Neck, R. 1996. Butterflies of Texas. Houston, Texas: Gulf Publishing Company.
New, T. 1991. Butterfly Conservation. New York, New York: Oxford University Press.
Scott, J. 1986. Butterflies of North America. Stanford, California: Stanford Press.