VIII GENUS SLL TICS. 203 
GENUS PSITHYRUS, Lepeletier. 
Synonym :—Apathus (Newman). 
Distinction between Bombus and Psithyrus. 
QuEENs. — Psithyrus queens may be readily 
known from Bomdbus 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, 
Bombus 
lapidarius 



Psithyrus 
rupestris 

Fic. 29.—Hind leg of Bomdus and Psithyrus female. 
though not thickly, with hairs, not flattened, bare, and 
shining in the middle as in Lomdus; and the comb 
at the apex of the tibia and the auricle at the base of 
the metatarsus being absent. 
In the Pszthyrus queens the apex of the abdomen 
is more or less incurved, and close to it, on the 6th 
ventral segment, z.c. 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, 
