Pontia occidentalis, the western white, is a butterfly in the family Pieridae. It is found in Western North America.

The wingspan is 38 to 53 millimeters. The host plants are from the Brassicaceae (mustard or cabbage) family. The caterpillars eat especially the flowers, buds and fruit. In the north of the range, one generation flies in June and July; in the south two generations fly from May to August.


source - Wikipedia