Satyrium sylvinus dryope
The tailless Satyrium sylvinus dryope flies from southwestern Kern Co. (around Mt. Piños, Frazier Park) into SLO, Santa Barbara, Ventura, and into western Los Angeles Counties (in at least part of the Santa Monica Mountains). There may be blending with desertorum as you get into the San Gabriels. These hairstreaks use willows as their host, and are thus a butterfly most likely to be encountered near creeks and drainages where the host does well.
First described as Thecla dryope - a full species - by W.H. Edwards in 1870, it's now considered a subspecies of Satyrium sylvinus. The type locality is Santa Clara Co., CA.; see the article below by Brown, "The Types of the Lycaenid Butterflies Described by William Henry Edwards. Part II: Theclinae and Strymoninae," in Transactions of the American Entomological Society from 1970.