Northern White Skipper
The Northern White Skipper can be common in rural southern California, seemingly anywhere mallow-family plants such as Sphaeralcea ambigua (Apricot Mallow) thrive. Males are nearly white; females much more darkly patterned. Females oviposit on young mallow leaves, which is where the larvae feed and create protective nests by rolling up the leaves. They fly much of the year (March to November in some places), but seem especially common in the fall.
This is another "gold rush" butterfly named by Boisduval in 1852 from those collected by Pierre Lorquin. According to Emmel, Emmel, and Mattoon (Systematics, p.20), Lorquin likely collected this butterfly in the northern Sierra Nevada foothills. The type locality was therefore restricted to "the vicinity of Sawmill Creek at Griffin Gulch, rim of West Branch Feather River, 2 air miles E. of Magalia, Butte County, California."