Operopherta can be difficult at the best of times to discriminate from each other. O. occidentalis can be distinguished from O. bruceata simply by location, the former occupying a strip along the coast of BC, Washington, and Oregon otherwise unoccupied by the latter (see maps at BOLD: BOLD:AAA2999, BOLD:AAA3000).

Recognising O. brumata however can be somewhat problematic. In BC. they seem limited to the greater Vancouver area and southern Vancouver Island (Victoria and Port Alberni). O. brumata has an earlier season (Nov) but still overlaps that of O. occidentalis (Nov-Jan). That would seem to identify December and January observations as occidentalis.

There is however the question of interbreeding. O. brumata and O. bruceata cross-breed in other locations where they occur together. The same might be true with O. occidentalis which could affect appearance and/or flight time.

Operopherta danbyi has also been recorded from BC but little information is available except they also have a striking resemblance to O. occidentalis.