Satyrium saepium
Hedgerow Hairstreak

Family Description:
Alternate Common Name:
Buckthorn Hairstreak.

Caterpillar: The caterpillar is light green and covered with short silvery hairs. Each side is marked lengthwise with a yellow stripe and faint greenish yellow ">"-shaped spots. It reaches a full-grown length of 1/2 to 3/4 inch.
Adult: The butterfly is fairly small, with a wingspan of 1 to 1 3/8 inches. The upperside is metallic golden to reddish brown and outlined in black. Males may have a black or gray spot near the leading edge of the forewing. The underside is brown and not as metallic. It is lightly marked with an irregular brownish black line, edged with white, which runs vertically across the center of both wings; the outer half of the wing may be lighter than the inner half. There is a row of brownish black dots near the wings’ edge. The underside of the hindwing is marked with a grayish blue spot or patch, and a thin tail originating near the spot extends from the rear. This tail tends to be longer in females than males, but in comparison with other Hairstreaks is quite short.

This species ranges from southern British Columbia south to Baja California, and east to central Montana, northwestern Wyoming, and in patches of Utah, Colorado, and the southwest. It occurs in patches throughout Idaho.

It occurs in dry, shrubby areas, including chaparral, sagebrush steppe, oak woodlands, and ponderosa pine forests.


Caterpillar: Caterpillars feed on the leaves and flower buds of buck brush (Ceanothus spp.) and possibly mountain mahogany (Cercocarpus spp.).
Adult: Butterflies drink flower nectar, often from yerba santa (Eriodictyon spp.), buck brush (Ceanothus spp.), and wild buckwheats (Eriogonum spp.).

Eggs are laid in the fall, overwinter, and hatch in the spring. There is one generation of caterpillars each year. Each caterpillar undergoes four stages of growth, called instars. The caterpillar is equipped with a honey gland, also known as a dorsal nectary organ, which emits a sugary solution agreeable to ants. The ants feed on the solution and in turn protect the caterpillar from predators. To feed, caterpillars cut holes in the upper side of leaves. Adults generally fly from mid-May through August. Butterflies may be found in large groups. The tails of the two hindwings resemble antennae and may act to fool predators into biting the wrong end of the butterfly allowing it to escape.

Males perch on short shrubs to wait for receptive females. Pale green eggs are laid singly on the branches, leaves, and flower buds of buck brush (Ceanothus spp.).

Idaho Status: Unprotected nongame species.
Global Rank: G5; populations are widespread, abundant, and secure.

Ballmer, G. R. and G. F. Pratt. 1988. A survey of the last instar larvae of the Lycaenidae of California. Journal of Research on the Lepidoptera 27:1-81.

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.