The recent discovery of a new Colias species from the central Arctic of Canada, a region with a relatively small, well-studied butterfly fauna, has remained relatively unknown among North American lepidopterists. The status of this species, C. rankinensis Verhulst, as a species distinct from other Arctic Colias has also been treated with skepticism. Colias rankinensis was documented from only a ... [Show full abstract] single locality globally, from a region where thousands of Colias specimens were collected during the Canadian Northern Insect Survey in the 1950s, as well as later in the 1980s. Many of these specimens were subsequently examined during the course of revisionary work on the genus Colias in the 1980s. In light of the discovery of C. rankinensis, the identification of central Arctic Colias 'hecla' specimens is critically re-examined, revealing that two phenotypes, corresponding to C. rankinensis and C. hecla Lefèbvre, occur sympatrically in the central Arctic. A differential diagnosis, adult illustrations and distribution map of C. rankinensis is provided, and the taxonomies of C. hecla taxa are reviewed.