Bombus mucidus was considered formerly as a distinct subgenus (Mucidobombus).
Bombus mucidus is restricted to the south European Mountains : Sierra Cantabrica, Pyrenees and western Alps for the ssp. mollis, rest of the Alps, central Appennino Mts, Balkan mountains (Bosnia, Crna Gora and Macedonia), central Carpathians for the ssp. cf. mucidus. The ssp. pittioniellus, of yet unsettled status, is restricted to the mountains of Crna Gora and Macedonia.
The local density of B. mucidus is highly variable. In some mountains e. g. in the eastern Pyrenees, it may be quite common whereas it is very rare in a large part of the Austrian Alps.
P. Rasmont