Santa Fe Dam Recreation Area, Irwindale, Los Angeles County, California, USA
May 6, 2008
Size: 6.5 mm
Perhaps Dioxys? Seen on sandy ground in So. Cal. Alluvial Scrub.
I'm still looking for more of these, though haven't seen them lately.
Finally went back to this site (May 10-11, 2016) , observed an sample this bee. My size estimates, based on perception on the ground, were wrong! In hand the female is about 6.5 mm in length (instead of first estimate of 4-5 mm). Looking at my male specimens, as well as one female, also reading Michener's description of specimens from Altadena, CA, I think this may well be Hesperapis rufipes. Still have to compare with identified specimens. Will post photos later.