The Western Tailed-blue (Cupido amyntula) is a member of the Lycaenidae family and is seen across western North America as far norther as Alaska. The upperside of the male butterfly is blue while the female has a darker brown band on the outer side of the wing. The underside is riddle with black spots, with a wingspan of 2.2 to 2.9 cm. The larvae feed on Thermopsis, Astragalus, Oxytropis, Vicia, and Lathyrus.