Western Tailed-Blue
Everes amyntula
Description
7/8-1 1/8" (22-28 mm). Above, bright lavender-blue with very narrow dark margin; female more brown and black than blue. Below, chalk-white, with grayish markings hazy and reduced, sometimes absent; orange spot above threadlike HW tail inconspicuous, sometimes absent.
Similar Species
Eastern Tailed-blue grayer beneath with more prominent dark and orange spots.
Life
Cycle Egg pale green. Caterpillar varies from straw-color to jade-green; has transverse mauve and maroon side slashes, and short fine white hair; feeds on locoweed (Astragalus), peas (Lathyrus), and vetch (Vicia). Mature caterpillar overwinters in seed pots of
host plants. Chrysalis, white haired, dingy white or brownish-yellow; egg-shaped.
Flight
2 staggered broods at lower elevations and latitudes; January-September, peaking in May and June in California. 1 brood at higher elevations and farther north; June-August.
Habitat
Moist meadows, canyons, and along roadsides, sandy clearings, and forest margins.
Range
Alaska south to Baja California and Mexico, east across Canada to N. central states, and south in Rockies to Arizona and New Mexico.
Discussion
This butterfly largely replaces the Eastern Tailed-blue in the West and in mountains. Offshore, it often abounds on the California Islands in far greater numbers than are normally seen on the mainland. As they drink, tailed blues twitch their hind wings in a way that calls attention to their threadlike tails, possibly distracting predators from attacking the body.
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