The bumblebees of the Italian western Alps

The western Alps extend from Bocchetta di Altare to the Splügenpass. They belong to France and Switzerland on the external side and to Italy on the internal one. The boundary runs mostly on the watershed between the Po basin and the Rhone and Rhine basins, except for the upper Ticino valley that belongs to Switzerland. Bumblebee faunas of France and Switzerland are much better known than the Italian one. That is especially true for the Italian western Alps, where only the "Waldensian Valleys", a small area in the Turin district, were thoroughly investigated in the years 1946-1970; information on the remaining area is rather old and scanty. Therefore, in the late nineties we started a survey of bumblebees of the Italian western Alps in order to ascertain actual species distribution and, whenever possible, the changes occurred in the last decades due to anthropogenic disturbance, habitat alteration, and global warming. Until now, several localities were sampled throughout the area, but our efforts were mainly focused on the Susa valley in the years 2000-2006 and on the Aosta valley in 2009. Available data, both from the literature and our investigations, were subdivided according to the administrative districts and grouped, in each district, on a chronological basis (until 1970, 1971-1995, 1996-today). Information appears concentrated mostly in the region Valle d’Aosta and in the province of Turin, which are located centrally in the western Alps, and rarefies moving on either side with the remarkable exception of the Canton Ticino in Switzerland.