AdultThe upperside of the wings of the male Western Spring Azure are a uniform violet blue with a narrow white margin and no orange or dark areas on either wing. The underside of the wings is a dirty chalk white, with the pattern of dark spots varying from mostly inconspicuous to very contrasting. Every population has a variable pattern on the underside of the wings. The female is similar to the male except that the dorsal forewings have wide black margins and the dorsal hindwings have a row of black marginal spots. The blue is much reduced, but is violet blue.
Immature StagesThe literature on this species complex is very confusing, but apparently the immature stages of the Western Spring Azure have not been described except for last instar larvae (Ballmer and Pratt 1989). The ground colour of the mature larva can be white, pale pink, or pale green. Lateral lines or chevrons are absent, but there is a conspicuous transverse bar on the first abdominal segment.
SubspeciesPopulations in BC are the nominate subspecies, C.e. echo (W.H. Edwards, 1864) (TL: San Francisco, CA) (= nigrescens Fletcher, 1903; TL: Kaslo, BC).