Callophrys [Incisalia] mossii
Moss' Elfin

Family Description:
Alternate Common Name:
Stonecrop Elfin.

Caterpillar: The caterpillars are generally reddish or pinkish in color, but may be yellow or green; they are covered with short brownish hair. Markings may include two reddish bands along the back and whitish diagonal dashes on the sides. The average, full-grown length is 3/4 inches.
Adult: This is a small butterfly, with a wingspan of 7/8 to 1 1/8 inches. The male is gray to brown on the upperside, and may be marked with a rust patch on the hindwing. The female is light to reddish brown, and may be outlined in dark brown along the edges. Underneath varies in color from red brown to purple brown to light brown. The underside of the hindwing is typically darker where it attaches to the body. Underside markings include a vertical wavy line running across both the fore-and hindwings, followed by a gray to white band and a row of black dots.

This species occurs in patches of British Columbia south to southern California and Arizona, and east through the Intermountain West. In Idaho, it has been documented to occur in patches of the western third of the state.

It occurs in canyons, rocky slopes, and sagebrush steppe.


Caterpillar: Caterpillars eat the leaves, flowers, and fruits of members of the stonecrop family (Crassulaceae), including various species of Sedum, Dudleya, and Parvisedum.
Adult: Butterflies presumably drink flower nectar, but the adult food has not been reported in the literature.

Young caterpillars feed preferentially on leaves while older caterpillars feed on flowers and fruits. There is one generation of caterpillars each summer. Each 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. Pupae overwinter in a physiological state called diapause. Adults generally fly from the end of February through May.

Males perch to wait for receptive females. Females lay pale bluish green eggs on the underside of the leaves of host plants. The eggs turn white before hatching.

Idaho Status: Unprotected nongame species.
Global Rank: G5; most populations are widespread, abundant, and secure. One subspecies in California, C. mossii bayensis, is listed as T1, which means it is critically imperiled because of extreme rarity and is imminently vulnerable to extinction.

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.