Bombus mesomelas belongs to the pomorum-group (formerly sg. Rhodobombus).
Within the West-Palaearctic region, Bombus mesomelas is a species from the southern mountains. Bombus mesomelas mesomelas is found in the Cordillera Cantabrica (Spain), the Pyrenees, the Alps, the Appennino Mts., the Tatras Mts., the Krkonoše Mts. (Czechia) and the Carpathians.
The range of Bombus mesomelas alboluteus is discontinuous, with a western population in the mountains of S. Bosnia, Yugoslavia and the Balkan and an eastern population in E. Anatolia, the Caucasus, Transcaucasia and N. Iran.
In the north of its range, mesomelas has been found in the hills and lower mountains of Thüringen (Austria), S. Poland and Bohemia (Czec Republic). All these findings are ancient. In the Cordillera Cantabrica, the Pyrenees, the western and central Alps, the species is quite common. On the contrary, in the eastern Alps and in the mountains of central-east and eastern Europe, as well as in Iran, mesomelas is uncommon and its distribution is patchy.
P. Rasmont