Euphilotes enoptes
Dotted Blue

Family Description:

Caterpillar: The appearance of the caterpillar varies. It can be offwhite to yellow to pinkish in color, and may be marked with pink to brown stripes, dashes, or other marks. The body may be hairy. Its average, full-grown length is approximately 1/2 inch.
Adult: This is a small butterfly, with a wingspan of 3/4 to 1 1/8 inches, and its appearance varies. Males are generally bright blue on the upperside, with the wings edged with black. The black edging may be spotty on the hindwing, and there may be an orange band in from the edge. Females are brown on the upperside and have an orange band near the edge on the hindwing. Both sexes are gray to white underneath and marked with black spots. The fore- and hindwing may each have black spots in rows along the edge; the hindwing often has an additional row of orange spots. The fringe on the wings is checked with black and white.

This species is found in patches of the western U.S., from Washington east to Montana, and south to California and northern Arizona and New Mexico. In Idaho, it occurs primarily along the eastern and southern borders.

It tends to occur in drier areas, often in sagebrush steppe, chaparral, open woodlands, and desert.


Caterpillar: Caterpillars feed on the flowers and fruits of various species of wild buckwheat (Eriogonum spp.).
Adult: Butterflies drink flower nectar, often from host plants.

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. Also for protection, the caterpillar bears a pair of everscible tubercles or tentacles on the eighth segment. These tubercles are usually housed within the body, but when the caterpillar feels threatened by the approach of a potential predator, they can be pushed out to release a chemical which mimics an ant alarm pheromone. This scent causes the ants to become frenzied and aggressive, and the potential predator takes leave or is eaten by the ants. There is one generation of caterpillars each summer. Each caterpillar undergoes four stages of growth, called instars. Pupae overwinter in a physiological state called diapause. Adults generally fly from mid-May to October. Butterflies do not fly far from where they emerge during their lifespan and the entire lifecycle of this species is spent in close proximity to wild buckwheat. The subspecies E. enoptes smithi, Smith’s Blue, was one of the first insects to be listed as Endangered by the U.S. Fish and Wildlife Service. A resident of the coastal dunes of California, it has been severely impacted by loss of habitat.

Males actively patrol near host plants in search of receptive females. Females lay eggs singly on the flowers or flower buds of host plants.

Idaho Status: Unprotected nongame species.
Global Rank: Varies with subspecies. Subspecies smithi of California is ranked as T2, imperiled and endangered because of rarity and/or because of other factors making it very vulnerable to extinction.


Arnold, R.A. 1983. Conservation and management of the endangered Smith’s Blue butterfly, Euphilotes enoptes smithi (Lepidoptera: Lycaenidae). Journal of Research on the Lepidoptera 22:135-153.

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.