There were many of these bees (and other species) energetically swarming over a vibrantly flowering patch of Phacelia exilis on a warm, calm, sunny afternoon, along an open road in montane coniferous forest.

I'm guessing these are Osmia. Their color seemed to vary from deep metallic green to a shiny bronze, depending on angle, light and individuals.

Interestingly, although there were many bees busily visiting the large number of P. exilis flowers here...the stamens of most the flowers present seemed to be largely devoid of pollen. There were just a few flowers whose anthers had appreciable visible pollen, or were just shy of being ripe...the vast majority looked spent. Perhaps that was because so many of these bees had so very effectively harvested the pollen already...and the bee visits I was seeing at that moment were mainly trying to reap the last morsels of pollen left?

[Note: There is more than one individual in this series: I'm not following the usual BG convention in this post, for purposes of easy cross-reference among the images. I'll separate them if it becomes necessary.]