Everes comyntas
Eastern Tailed-Blue

Family Description:
Alternate Common Name: Tailed Blue.

Caterpillar: Caterpillars are variable in color, often green to brown with a row of dots or a stripe on the sides, and hairy. The average, full-grown length of the caterpillar is 1/2 inch.
Adult: This is a small butterfly, with a wingspan of 3/4 to 1 1/8 inches. The male is silvery blue on the upperside with a black line edging the wings. It is gray to white underneath with a curved band of small black dots and two to three large orange spots at the bottom of the hindwing. The female is blue in spring and more brownish on the upperside in summer, with similar markings as the male. Both sexes have a white fringe and a thin tail off the hindwing.

This species is found east of the Rockies, from southern Canada to Central America. It may also occur in patches in the intermountain west and southwestern U.S. Eastern-tailed blues occur in isolated sections of northern and west central Idaho.

Adults occur in open areas, particularly those recently disturbed.


Caterpillar: Caterpillars feed on the buds, flowers, seeds, and sometimes leaves of legumes, including species of clover (Trifolium spp.), alfalfa (Medicago spp.), pea (Lathyrus spp.), vetch (Vicia spp.), and bean (Phaseolus spp.).
Adult: Butterflies obtain nectar from relatively short plants with open, shallow flowers, such as wild strawberry (Fragaria spp.) and white sweet clover (Melilotus alba).

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. Caterpillars overwinter within the pods of host plants in a physiological state called diapause, and pupate in the spring. Each year, there are three generations in the northern part of its range and many generations in the south; in the case of multiple generations during a given summer, only the caterpillars of the last generation overwinter. Each caterpillar undergoes four stages of growth, called instars. Adults generally fly from March to December. This is one of the few members of the family Lycaenidae that can be found resting with its wings open.

Males patrol near host plants for receptive females. Females lay eggs on flower buds and stems.

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. http://www.npwrc.usgs.gov/resource/distr/lepid/bflyusa/bflyusa.htm (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.