To bee, or not to bee?

After church, I wandered down to the big Commonwealth Cemetery, thinking, the sun was shining - I might get some good shots for Cemetery Sunday. 

My eyes were drawn to a very overgrown patch of heather, which was steadily obliterating a couple of graves. I'd an idea of using the heather as a foreground - when I noticed the bees. So I couldn't resist. I can't quite decide if this is a tree bumble bee, or common carder. He was quite small, and very quick - but obviously doing a good job, as you can tell by the size of his pollen sack.