This insect looks and acts like a carpenter bee, pierces the calyx of flowers in order to get at the nectar (here Salvia microphylla in my garden). Faster flier than the Valley Carpenter Bee. Spent most of the time flying around the Sages in my garden, or chasing others of its kind (I observed three or four).

Just returned from the Entomology Research Museum, UC Riverside. Doug Yanega (UCR Entomology Research Museum, Riverside, CA), who provided the ID, showed me specimen of both X. californica and X. tabaniformis. It is clearly X. tabaniformis by size, color (the metallic sheen in my images is probably an artifact of reflected light), including the thoracic pile, and the yellow face of male specimen. Specimen of X. micans are similar, also in size, but from the southeastern US, e.g. Florida. X. californica is larger, black, with a dark blue cast on the lower abdomen.
Records for this species in Southern California include Pasadena, La Crescenta, and Burbank (The Carpenter Bees of California, by Paul D. Hurd, Jr.; Bulletin of the California Insect Survey, vol.4, no.2. 1955).