Papilio eurymedon
Pale Swallowtail

Family: Papilionidae
Family Description:
Alternate Common Names:
Pale Tiger Swallowtail, Pallid Tiger Swallowtail.
Some authors use an alternate genus name for this species, Pterourus. Occasionally the older genus name, Euphoeades, may still be used.
The caterpillar is green (brown right before pupating) with a brownish head. It is marked with two yellowish eyespots with blue centers towards the head, followed by a yellow and black band across the "neck", and several longitudinal rows of small blue dots along the body.
Adult: This is a large butterfly, with a wingspan of 3 inches, and it bears the characteristic long "tail" extending from the rear of the hindwing. The upperside is white or cream and marked with wide, diagonal and almost parallel black bands. The black wing borders may have a row of white bars. The rear of the hindwing is marked with several patches of blue and orange. Underneath is similarly marked but may be paler; the wing veins are dark.

This western species ranges from southern British Columbia south through the Pacific Northwest to southern California and northern Nevada; and from northern Idaho and western Montana south to central Utah and northern New Mexico.


It occurs in open, hilly areas, often with chaparral and scrubby woodlands; often found upslope, towards hilltops.


Caterpillar: Caterpillars feed on the leaves of a variety of trees and shrubs, including cherry (Prunus spp.), coffeeberry (Rhamnus spp.), and particularly Ceanothus species such as wild lilac and mountain balm.
Adult: Butterflies drink flower nectar.


Caterpillars construct silken mats attached to leaves which they rest on while feeding. There is only one generation of caterpillars each year in most of its range; there may be several in southern California. A pupa’s color depends upon the number of hours of sunlight (photoperiod) the pupa is exposed to, with pupae from the long days of summer being green and those from later in the season being brown. Late season pupae overwinter in a physiological state called diapause. Adults generally fly from late April through July in most of its range. Adults can often be found "puddling" on muddy spots or moist dung where they collect salts and other nutrients.


Males actively patrol in search of receptive females, but may occasionally perch to wait for them to pass by. Courting males and females will often congregate at high points in the landscape in order to find potential mates. This behavior is called "hill topping." Females lay 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.