Bombus ruderarius
Bombus ruderarius is a medium-small size bumblebee (length in queens: 16-18 mm; length in males 12-14 mm).
The head is moderately elongated, due to the smaller malar gap (which shows a scarce and thin stipple) than the distal width.
Females show a prominent clipeum with thin but dense stipple. The labrum’s groove is shallow and widened at the base, and it shows a shiny forehead. The hind legs doesn’t show reticulated tibias. The genitalia in females is similar to that of Bombus sylvarum.
Males show a long and dense bearded jaw, and a clipeum scarce dotted. The tibias in hind legs are shiny and have long chaetas.
The queens surfacing takes place in May. The nest is superficial, between vegetation, mosses, grass, in hayfields, even in manure for gardens. The colonies compose of 25-30 to 48 individuals. The flight period covers from May to September, and the biotopes are the edges of forests, but it is also adapted to bare lands in mountains.
Females: the head is moderately elongated, due to the smaller malar gap (which shows a scarce and thin stipple) than the distal width. The malar gap shows a barely and thin stipple. Females show a prominent clypeus with thin but dense stipple, unequal at discus. Apical impressions well defined, constituted by pits of different sizes. Plane labrum's tubercles, and only upper dotted. Shallow labrum's groove. Shiny forehead. In the hind legs, tibias are not crosslinked, the basitarsus wider in the proximal than in the distal zone. T4 y T5 provided of big pits. The intermediate gaps are matte, because of the existence of a microrelief. T6 with a thin stipple. Genitalia similar to that of Bombus sylvarum. External projections of the stinge case are wide.
Males: the head is moderately elongated, due to the malar gap is slightly longer than its distal width (like A3+4). Males show a long and dense bearded jaw, and a clypeus scarce dotted. Flagellomeres of the antenna asymmetrically thickened in the lower region. Length of A3, at least, two thirds of A5. A5 slightly smaller than A3+4. Convex and bright tibia on hind legs, provided of long chaetas, whose length doesn't exceed the maximum width of the tibia. E8 very pubescent. Genitalia with hooked and diverging sagittae, slightly sawn at the tip, prolonged in a small lower tooth. Squama provided of a long tooth in its inner part.
The range of Bombus ruderarius extends over a large part of the western Palaearctic region, with preference for mountain range in Iberian Peninsula, avoiding the high average temperatures in summer. The abundance of this species ranges from low (north of Africa) to very heavy (eastern Pyrenees).
Potential distribution map at the present time
Potential distribution map in 2050 with the same level of pollution emission and the climate changes consequence of these contamination levels
Map legend
Maps are made with GBIF data of this specie in Iberian Peninsula
It shows preference for the edges of the forests in mountain range, where it is also able of inhabiting montane bare lands.