VIII GENWSI2Sa7TAY ROS 205 
Matrs.—The beginner does not find it easy to 
distinguish the Pszthyrus males from those of 
Lombus, there being no very striking characters 
to rely upon. At first glance they differ most 
noticeably in their somewhat thinner and coarser 
coats, and particularly in their more shining, because 
less densely-clothed, abdomens. When the Ist segment 
is clothed with yellow hairs the brightness of the 
yellow is reduced by the black skin underneath. 
The face is rounder and shorter than in the males 
of most species of Bomdéus. The forceps of the 
armature are pale and membranous, while in Lomdus 
they are brown and horny. Some of the best dis- 
tinguishing characters are to be seen in the hind 
tibie: these, as in the females, are, on the outer 
side, transversely convex and hairy all over, while in 
the males of Aomdus the tibiz are flattened, bare (or 
almost so) in the centre, and more shining than in 
Psithyrus, except in the males of the carder-bees, 
which in respect of these tibial characters occupy 
an intermediate position; but as the males of the 
carder-bees have the joints of the antennz swelled 
underneath (only the last six joints in B. derha- 
mellus and BL. syfvarum), a peculiarity not found in 
the Pszthyrz and in the other Bomédz, they can easily 
be excluded from comparison. 
