1/2-3/4" (13-19 mm). Tiny. Male light blue above with thin black border; some males have white on HW. Female white above, often with blue near border; broad brown-black margins and inner banding and black HW spots. Both sexes translucent, with underside markings showing through. Both sexes pale white below, with brown bands profusely scalloping FW and inner HW, fading away into pale patches in basal wing halves; spotted brown borders, 2 marginal HW spots.
Antillean Blue has dark markings beneath, more in short bars than extended bars; usually only 1 black HW spot. Marine Blue purplish-blue above, complete bold brown scalloping below.
Egg pastel green changing to ivory. Young caterpillar dark yellow, becoming speckled green suffused with russet; feeds on flowers of leadwort (Plumbago), milk pea (Galactia), lima bean (Phaseolus limensis), rattlebox (Crotalaria), and other legumes. Chrysalis attached to lower leaf surfaces by silken girdle.
Multiple broods; most months where resident, summer and autumn where emigrant.
Fields, roadsides, and parks.
Resident in S. Florida and S. Texas, emigrating through Kansas and Missouri; south to South America.
Very common in the southern part of its range, the Cassius Blue flies in almost any sunny spot. Adults seem to prefer flowers of trees and shrubs. Although this species maintains northern populations during moderate weather, it still succumbs to frigid midwestern winters.