Strymon istapa clenchi
Mallow Scrub Hairstreak
This uncommon hairstreak was described by G. Austin and J. Emmel as a subspecies of Strymon columella in the 1998 Systematics book. It flies in "extreme southern California" and into Nye Co., Nevada, southern Arizona and into Baja California, Mexico (and possibly into mainland Mexico as well, the authors say). The type locality is Blythe. The flights are from early spring all the way to November. This hairstreak feeds on mallows in the larval stage. Malvella leprosa is mentioned in the description, but Gordon Pratt says it prefers Hibiscus denudatus in the desert, where it can use Sphaeralcea species as well.
The life cycle of this butterfly was described by John Comstock and Charles Dammers in a 1935 article in the Bulletin of the Southern California Academy of Sciences ("Notes on the Early Stages of Three Butterflies and Six Moths from California," v.34, pp.120-123). I've excerpted in below from the copy on the BHL website.