We've been seeing these bees for days. Several fly near and through a blooming cliffrose and a around golden chain blossoms. They seem to spend all their time chasing each other, and they rarely land on a blossom. They're very fast-moving, so I captured one and took these photos through a glass cloche. I have shots from very brief moments when the bee walked instead of buzzing angrily. After finding good images of Xylocopa tabaniformis for this tentative ID, I'm not sure where the "horsefly-like carpenter bee" gets its common name. Flying behavior? I have other images that show the glossy black abdomen.