I finally figured out what kind of digger bee this little one is, an Anthrophora curta.
Until now I only observed Ivory Banded Digger Bees Anthophora californica.
So this is a very exciting discovery for me.
Digger bees are solitary and nest in the soil.
Their preferred flowers are lavender, as this one is demonstrating, and salvia.
But these particular digger bees often can be found on asters, coreopsis and daisies.
The distinguishing characteristics of the Anthophora curta are the thick hairy hind legs and thick whitish bands on the abdomen.