Strymon melinus
Gray Hairstreak

Family Description:
Alternate Common Name:
Common Hairstreak.
Caterpillar: The caterpillar varies a great deal in color, and can be either yellowish brown, pink, green, or reddish brown. It is marked with light diagonal stripes on the sides. It reaches an average, full-grown length of 5/8 inch.
Adult: This is a fairly small butterfly, with a wingspan of 7/8 to 1 3/8 inches. There is a thin tail extending from the rear of the hindwing. The upperside is dark gray to brownish gray and marked with a single large orange spot on the rear of the hindwing near where the tail originates. The underside varies in color from dark to light gray, and is marked with a thin, vertical line of black dashes, edged with white, running across both wings. The outer edge of both wings is marked similarly but more faintly. The underside of the hindwing is marked with one or two orange patches and two black spots at the rear. Males are marked along the sides of the abdomen with orange.

This butterfly exhibits a large range, extending from southern Canada, throughout the entire U.S., south through Mexico into South America. It occurs in sections of Idaho, primarily in the panhandle and the southwest.

It occurs in many kinds of open, often weedy, areas, including open woodlands, chaparral, along coasts, and in fields and vacant lots.


Caterpillar: Caterpillars eat the flowers, fruits and occasionally young leaves of a large array of both cultivated and wild plants representing over 15 different families. Cultivated species include corn (Zea mays), cotton (Gossypium spp.), bean (Phaseolus spp.), alfalfa (Medicago sativa), and hops (Humulus spp.).
Adult: Butterflies drink nectar from a wide variety of flowers.

The number of generations of caterpillars each year varies with location, with there being two in the north and up to four in the south. 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. The caterpillar is referred to in parts of its range as the "cotton square borer," and it can cause significant damage to crops when feeding in large numbers. Pupae overwinter in a physiological state called diapause. Adults generally fly from March to November.  The tails of the two hindwings of the butterfly resemble antennae and may act to fool predators into biting the wrong end of the butterfly allowing it to escape.

Males perch on trees and shrubs in the afternoon and evenings to wait for receptive females. Eggs are laid singly on the flowers of host plants.

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.