Colias scudderii, the willow sulphur, is a butterfly in the family Pieridae. It is found from Alaska south through the Rocky Mountains to northern New Mexico. The habitat consists of mountain meadows and willow bogs.[1]
The wingspan is 38mm51mm. Adults are on wing from June to August. They feed on flower nectar.[1]
The larvae feed on the leaves of Salix species (including Salix reticulata, Salix lutea and Salix planifolia). Second, third, and fourth instar larvae hibernate.[1]