...or as Lynn Monroe described them "exquisite"!

I had read about Perdita in "The Forgotten Pollinators", where the authors discuss how they're among the tiniest of bees and, as pollinators, can be associated with a single plant species. I wonder if the ones I saw were males, as they were just lazing around on the corollas, rather than busily moving from flower to flower collecting pollen.

You may still be able to find these bees out in the desert east of you now. [Note: I corrected the date for these images from 1/31/10 (typo!) to 3/31/10...a bit under 3 weeks ago.] You can look for Mentzelia involucrata patches, which were especially abundant this year in the wilds north of Salton Sea. There may be more blooming now in Joshua Tree, as it's a bit higher elevation, and thus usually later in phenology. According to the Jepson Manual, M. involucrata generally blooms from January to May, depending on the location (and the year).

And Lynn found yellow Perdita visiting flowers of Honey Mesquite (Prosopis glandulosis), a more widespread and common desert plant which, being a woody tree, typically has a longer blooming period.

Good Luck!

The first ones I ever saw were males and much smaller than the females. Behavior was similar to what you described.

...for the ID's of both Perditas.