VIII 



GENUS PSITHYRUS 



20 



GENUS PSITHYRUS, Lepeletier. 



Synonym : Apathus (Newman). 



Distinction between Bombus and Psithyrus. 



Queens. Psithyrus queens may be readily 

 known from Bombus queens by the absence of the 

 pollen-collecting organs on the hind legs, the outer 

 side of the tibia being convex, dull, and clothed all over, 



Fig. 29. Hind leg of Bombus and Psithyrus female. 



though not thickly, with hairs, not flattened, bare, and 

 shining in the middle as in Bombus ; and the comb 

 at the apex of the tibia and the auricle at the base of 

 the metatarsus being absent. 



In the Psithyrus queens the apex of the abdomen 

 is more or less incurved, and close to it, on the 6th 

 ventral segment, i.e. on the last segment on the 

 underside, there is a pair of elevations, the shape of 

 which differs widely in each of the well-marked species, 



