Papilio rutulus
Western Tiger Swallowtail

Family: Papilionidae
Family Description:
Note: Authors address this species in several alternate ways. Some refer to it with the genus name, Pterourus. Occasionally it may be referred to with the older genus name, Euphoeades. Finally, it may be referred to as a subspecies of Papilio glaucus, the Tiger Swallowtail.
Caterpillar: The caterpillar is green, enlarged in the front, and marked near the head with four yellow dots and two yellowish eyespots with bluish centers. The "neck" is banded with black and yellow, and the body has several rows of tiny blue dots. The caterpillar turns brownish in the last stage prior to pupation. It can reach a maximum length of two inches.
Adult: The butterfly is large, with a wingspan of 2 to 4 inches, and tailed. The upperside is bright yellow and edged with a thick, black border. Each side of the butterfly is marked with four wide, diagonal, nearly parallel stripes; the innermost stripe is the longest, while the outermost two are simply bars. The hindwing has several patches of blue and only one or two spots or crescents of orange. Underneath is similarly marked; the hindwing is edged with a continuous blue line followed by a row of yellow bars, and there is little orange.

This species ranges from southern British Columbia and Alberta south through the western third of the U.S. to southern California, Arizona, and New Mexico; it ranges east as far as western South Dakota and central Colorado. It occurs throughout all of Idaho.

This Swallowtail utilizes a variety of habitats, including canyonlands, sagebrush steppe, woodlands, and gardens.


Caterpillar: Caterpillars feed on the leaves of several species of trees and shrubs: cottonwoods, poplars, and aspen (Populus spp.), willows (Salix spp.), alders (Alnus spp.), cherry (Prunus spp.), and ash (Fraxinus spp.).
Adult: Butterflies drink flower nectar.

Caterpillars construct small feeding structures from folded leaves tied and lined with silk. There is only one generation of caterpillars each year in those parts of its range with shorter summers, while there may be up to three generations where conditions are more favorable. Adults generally fly from June through July in most of its range, but from February to November along the coast of the Pacific and throughout the year in southern California. While this is the primary Swallowtail of the west, it has an eastern counterpart, Papilio glaucus, which occurs throughout Canada and the eastern half of the U.S. as far as central Montana, eastern Wyoming and Colorado, and central Texas. Papilio glaucus has recently been documented in Idaho, in Latah and Clearwater Counties. The two species may hybridize where they meet.

Males actively patrol in search of receptive females. Females lay shiny green eggs singly on the leaves of host plants.

Idaho Status: Unprotected nongame species.
Global Rank:

G5; populations are widespread, abundant, and secure.

Ferris, C. D. and F. M. Brown. (eds.) 1981. Butterflies of the Rocky Mountain States. Univ. of Oklahoma Press, Norman, Oklahoma, USA, 442 pp.

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.