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The combination of an orange upperside, halo-like ring around the discal spot of the hindwing underside, and row of submarginal spots will distinguish this species in most cases. Albino females are very similar to those of C. philodice, although slightly larger. There are no recognized subspecies.

The egg is initially white, turning red several days after being laid. Mature larvae are dark, velvety green with a red-bordered, white lateral line with yellow to red dashes (Guppy & Shepard 2001). Pupae are light green with a yellow lateral line and brown markings. This species fluctuates greatly in abundance from year to year, being rare or absent in some years and common in others; this is apparently the result of winter survival in areas to the south of Alberta, since the Orange Sulphur cannot survive the Alberta winters. Migrants of the Orange Sulphur appear in central Alberta in late June to early July; these migrants are larger than the summer brood they produce here, and are usually flight-worn by the time they reach Alberta. It is not known if individuals of the second brood attempt a southward migration, or if they perish during the first frosts.

Larvae feed on a wide variety of legumes, particularly non-natives such as clover (Trifolium) and alfalfa (Medicago sativa) (Guppy & Shepard 2001). There are no larval records of this species for Alberta, but these plants are the most likely hosts. Larvae sometimes reach pest levels in the southern portions of the range (Layberry et al. 1998). Adults take nectar at legume flowers, including alfalfa, and males mud-puddle (Nielsen 1999).