Papilio machaon
Old World Swallowtail

Family Description:
Alternate Common Name: Artemisia Swallowtail.
Caterpillar: The caterpillars vary in appearance both according to age and location. Young caterpillars are mottled with black, brown and white, looking much like a bird dropping (a good camouflage strategy). Older caterpillars are generally green and ringed with black, often heavily; the rings are dotted with orange, yellow, or red spots.
Adult: Butterflies vary in appearance as well, particularly in the amount of yellow and black present both above and below. They are fairly large, with a wingspan of 2 to 2 inches, and have a tail extending from the hindwing. Generally, the upperside is brownish black marked with yellow. A band of yellow, elongated spots spans across the wings; along the wings’ edges is a row of yellow bars. The part of each wing close to the body is black and is often hairy on the hindwing. The hindwing has a wide, curved band of blue; also present is an orange spot, outlined in black, possibly with the black curving into the center of the spot. The underside of the wings is marked similarly but more faintly; there may be more orange bordering the blue on the hindwing.

This species is holarctic, which means it can be found in parts of the northern temperate regions of the entire Northern Hemisphere. In North America, it ranges from Alaska across most of Canada, and from southern British Columbia through the western third of the U.S. to Arizona and New Mexico (not along the Pacific coast or in most of California). It has been documented in a number of counties in Idaho, scattered throughout the state. It is generally an uncommon butterfly.

It occurs in arctic and alpine areas, along forests, and on open hilltops.


Caterpillar: Caterpillars feed on certain members of the parsley family (Apiaceae), and on arctic sagebrush (Artemisia arctica). Young caterpillars eat leaves while older ones prefer flowers and associated structures.
Adult: Butterflies drink flower nectar.

There is one generation of caterpillars each summer in the northern part of its range, and two in the south. Pupae present in autumn will overwinter in a physiological state called diapause, and may remain in diapause for several seasons if conditions are unfavorably dry. Adults generally fly from June through July in the northern part of its range, and from April to September in the southern part of its range. Butterflies frequent the tops of slopes, a behavior called "hill topping." It is an important strategy for finding mates. This species has not been studied extensively in the U.S., and much of what we know comes from detailed studies conducted in Europe.

Males both perch and actively patrol to find receptive females, and spend most of their time on hilltops when seeking a mate. Females lay eggs singly on host plants.

Idaho Status: Unprotected nongame species.
Global Rank:

G5; populations are widespread, abundant, and secure.

Opler, P. A., H. Pavulaan, and R. E. Stanford. 1995. Butterflies of North America. Jamestown, North Dakota, USA: Northern Prairie Wildlife Research Center Home Page. (Version 05Nov98).

Opler, P. A. and A. B.Wright. 1999. A Field Guide to the Western Butterflies.   Second Edition.  Peterson Field Guide Series. Houghton Mifflin Company, New York, New York, USA, 540 pp.

Pyle, R. M. 1981. National Audubon Society Field Guide to North American Butterflies. Alfred A. Knopf, Inc., New York, New York, USA, 924 pp.

Scott, J. A. 1986. The Butterflies of North America. Stanford University Press, Stanford, California, USA, 583 pp.

Stanford, R. E. and P. A. Opler. 1993. Atlas of Western U.S.A. Butterflies (Including Adjacent Parts of Canada and Mexico). Published by authors, Denver, Colorado, USA, 275 pp.