White-tailed Bumblebees (Bombus lucorum) look very similar to Buff-tailed Bumblebees (Bombus terrestris) but are slightly smaller and the males have more lemon yellow hairs instead of orange-yellow.
In addition, White-tailed Bumblebees have a distinctive yellow nose.

First 3 photos: A male. In my yard, Hilversum, The Netherlands, 25 June 2013
Last 2 photos: A male. In my yard, Hilversum, The Netherlands, 9 July 2017