The Mt. Charleston blue butterfly is a distinctive subspecies of the wider ranging Shasta blue butterfly (Plebejus shasta), which is a member of the Lycaenidae family. The wingspan of the Mt. Charleston blue butterfly ranges from ¾ to one inch. The upper side of males is dark to dull iridescent blue and females are brown with a blue overlay. Their underside is gray, with a pattern of black spots, brown blotches and pale wing veins, which give it a mottled appearance.
The Mt. Charleston blue butterfly only occurs at high elevations (6,600 – 8,600 feet above sea level) primarily on the east side of the Spring Mountains in the Spring Mountains National Recreation Area of the Humboldt-Toiyabe National Forest, approximately 25 miles west of Las Vegas in Clark County, Nevada. The butterfly requires open habitats that support its larval host plant, Torrey’s milkvetch (Astragalus calycosus var. calycosus), which grows at elevations from 5,000 to 10,800 feet above sea level in the Spring Mountains. (USFWS photo/Corey Kallstrom)