Males of the Christina Sulphur can be recognized by the following characteristics: at least some bright orange on the upperside, but not extending all the way to the base of the forewing (as in C. meadii and C. canadensis), row of underside submarginal spots absent (usually) or weakly developed (rarely). Females are more difficult to identify with certainty because of the huge amount of variation they exhibit, both in ground colour (Orange, yellow, cream or white) and the extent of the dark border (nearly absent to well-developed). However, like the males, the underside spots are usually absent, and orange forms have a yellow forewing base. Our northern boreal populations are subspecies christina (Christina was described from northeastern Alberta), but designation of a subspecies to non-boreal populations remains uncertain (Bird et al. 1995).