Spotted several of these guys on our California lilac (Ceanothus sp.) and originally thought they were Lasioglossum sp., until I downloaded the photos (the actual bees moved far too quickly to examine in person). They appear somewhat similar to A. caerulea, so I was wondering if they are a kind of mining bee. Notes:

• ~7.5–9 mm (Ceanothus sp. blossoms average 0.25" across).
• Appear to be male (if I'm counting the antennal segments correctly).
• Black with metallic blue-green cast under light (not well shown in photos, sorry!).
• Wispy white hair on thorax and legs, some mixed white hairs on head/face and abdomen—the white hairs on the thorax were very noticeable and quite long. There also appears to be a tuft of white hairs on the last tergum.
• Mixed light brown/amber and black/charcoal hairs on parts of the head/face, legs, and abdomen.
• Very fast moving.

My apologies in advance for the photo quality, these were the least blurry photos I managed to get. Thanks!