Sorry, too blurry to tell.

Could they be mites?
See this website that discusses them
http://www.wildaboutbritain.co.uk/forums/insects-and-invertebrates/24066-bumble-bee-mites.html

About the only thing you sometimes see on Bees are a kind of mite, hitching a ride from one nest area to another. They are not harmful like the invisible to the naked eye Varoa mites. These ones do a garbage cleaning service for the bees.

I've never seen these before,interesting :)

They seem to be on the wings too. If they are mites they're sure in for a dizzy ride!

Unusual to see them now. You normally just see them on queens in the autumn or recently emerged queens in spring.

**pollen possibly?