Had the first two bumblebees in the garden on 23rd February this year, seemingly with one each of Bombus terrestris (rich/dark yellow bands and a buff tail) and B. lucorum agg. (pale yellow bands and a clean white tail) appearing on the heather. Both were accompanied by mites, the B. terrestris queen being well and truly infested, yuck/ewww, or so you would think, although, according to the Bumblebee Conservation Trust (BCT) website:
"... most of the mite species that live with bumblebees are fairly harmless to them and are simply clinging to the bumblebee so that they can be transported to new nests. When in the nest, the mites usually feed upon the wax, pollen, nest debris, and other small insects, so do not feed on the bees."So perhaps just meh.
White-tailed Bumblebee B. lucorum agg. This 'species' is actually a complex of three cryptic species B. lucorum, B. cryptarum and B. magnus. The tricky little buggers.
Buff-tailed Bumblebee B. terrestris
More on bumblebees on the BCT website here; at the Bees, Wasps and Ants Recording Society website here; and on the Natural History Museum website here.