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The Checkered White and the other two Pontia whites can be a challenge to identify. The Spring White (Pontia sisymbrii) is easiest to distinguish; the dark vein markings on the hindwing underside are not connected laterally, and it occurs only in montane woodlands and extreme northern Alberta. The Western and Checkered White (P. protodice) are more difficult to separate. Males of occidentalis are more heavily marked than protodice, particularly on the underside. Females of both species have heavier markings than the males, but these markings are brown in protodice, not charcoal or black. Another characteristic is found on the underside of the forewing apex: P. occidentalis has the dark submarginal band connected with dark markings along the veins to the wing margin, P. protodice has only pale yellow scales here. There are no named subspecies.

Guppy & Shepard (2001) summarize the appearance of the immature stages as follows: the egg is orange, and mature larvae are black dotted and bluish green to grey with a yellow dorsal, lateral and sublateral stripe. The pupa overwinters, and varies in colour from blue-grey to cream. The Checkered White is rare in Alberta, only occasionally appearing as a migrant from the southern U.S. There are no spring records for this species in Alberta (Bird et al. 1995), so it likely does not survive our winters (Scott 1986). Colonies are occasionally established for several years in southern Ontario north to the Ottawa Valley (Layberry et al. 1998).