It can be very difficult to tell Western Whites from Checkered Whites. But I’m reasonably confident this is a male occidentalis. Mostly judging by the charcoal Vs on the forewings and from distribution maps.

Sparks Lake, Deschutes County, Oregon

44.02529, -121.72862 We found a nice meadow area between Soda Creek and Soda Creek Campground at the north end of Sparks Lake. Although it was quite dry, there were abundant wild flowers in bloom and many butterflies.

July 9, 2023

Notes:

• Western Whites engage in hilltopping behavior for mating. Newly eclosed females fly up to rendezvous, then return downhill to find host plants for their eggs, preferring crucifers.
• Peak June, July and August.

Compare P. occidentalis in Washington, where I have observed both males and females.