The bees quickly entered burrows, so they were difficult to photograph. Eventually I found one digging, and caught a glimpse of its beautiful green eyes:
And then I spotted a female outside of a burrow:
And a male perched on a flower stem (below). Note his bright yellow face (it made the male easy to follow even when it was flying):
I'm pretty sure this is Anthophora californica. It's the first time I've photographed this bee. [You might remember that I showed a different species of Anthophora in 2013 — see the post called "Turrets and Tongues".]
Eventually, I also managed to photograph the wasp. I need to ask for some help with the identification, but I think it might be a "cutworm wasp," perhaps Podalonia (argentifrons?)? Impressively, the wasp was carrying a large caterpillar (perhaps a cutworm!):
And here's one more bonus picture. I'm not sure about the identity of this pretty little bee, but I'm wondering if it's a species of Andrena? This bee was so small and so fast, and the pollen on its legs was so dense and so bright, it looked as if a clump of pollen was flying among the vegetation! UPDATE (30 May 2016): Robbin Thorp has confirmed this as Lasioglossum sp.