The name is a misnomer, since this butterfly always breeds on Wild Buckwheats (Eriogonum, family Polygonaceae) and has nothing to do with lupines. However, under the International Code of Zoological Nomenclature, there's nothing one can do about that! The butterfly is very similar to the Acmon Blue, but unlike it, is always single-brooded. Although there are a few lower-elevation colonies in the Sierra, on our transect it occurs only from Lang Crossing (5000') upslope, flying generally in late spring-early summer (May-July). It may co-occur with the weedy, colonizing Acmon Blue, but generally on different host plants. Lupini is slightly larger; the male is brighter blue (less violet) and has a black inner border on the orange hindwing lunules above; beneath the ground color is more ashen, the black spots rounder and smaller but quite distinct, and the iridescent scales near the hindwing margin quite pronounced. The female may be quite blackish above and rarely has as much blue as the female cold-season form of acmon ("cottlei"). The Lupine Blue occurs with its host, often on rocky balds and in alpine and subalpine "rock gardens;" males puddle, and both sexes often visit Pussy Paws.