I'm trying to become more proficient in Bombus ID. Yellow vertex and yellow on T2 eliminates impatiens. Yellow vertex, thin hair on thorax, lack of brown band eliminates griseocollis. Yellow on T2 extends far from median, eliminating bimaculatus. Most of the perplexus I have seen are yellow on all abdominal segments, and brighter than this specimen. But I see photos of perplexus (males?) with black terga and overall paler yellow. How am I doing? And thank you for all the ID help.