A large number of Bombus sp using Lupine and California poppy
very large bumble bee feeding on a Salvia. Immediately struck me as unfamiliar. I'm not confident this is crotchii (which doesn't look like an eastern sierra species), but the placement of the yellow bands, the faint reddish tail end, and short looking cheek seems to suggest that species.
Location is 6,800' just west of Mono Lake - sage-scrub adjacent to the Sierra escarpment
A large bee visiting this sage, approaching the size of a female carpenter bee. Saw the bee land on poppies that were clearly too small for it, and they'd stoop over from the bee's weight.
Bumblebee on Asclepias eriocarpa
Nestled between rocks, moist soil
I don't think this is Triadica, but couldn't get back to suggestions...