Not being particularly knowledgeable about Bumblebees I'm hoping I've correctly identified this as (Bombus monticola)
If so it is an uncommon moorland species found in declining numbers in the north and north western highlands.
Often pollinating Bilberry, Cowberry and Cranberry.
I photographed this one this morning at map reference NH 30276 26364 at the margin of Pine Forest on Guisachan farm in Glen Affric.
My identification was made from information at www.bumblebee.org