180 
BRITISH BEES. 
bring the male within the boundary of the genus, nothing 
but experience, or specific description will associate the 
sexes correctly, there being in many cases an extraordi¬ 
nary discrepancy between them. These two genera 
themselves also can scarcely be distinguished apart, ex¬ 
cepting by means of their trophi; Cilissa, however, in 
general habit greatly resembles the genus Colletes, espe¬ 
cially the Cilissa tricincta, which might, upon a super¬ 
ficial glance, be almost mistaken for one of them. 
The male Halicti have long cylindrical bodies and 
long antennae, but from the male Chelostomu, which has 
a very similarly shaped body also and long antennae, 
they may be distinguished by the differences in the num¬ 
ber of the submarginal cells; and from those of Sphe- 
codes, by the antennae, which, in the latter are not rela¬ 
tively so long, and are usually moniliform. The thorax 
of these is also less pubescent, and the tinge of the red 
colour of their abdomen is different from that of the red 
male Halicti. 
The males of Ccelioxys can be readily distinguished 
from those of Megachile, by the spinose apex of their 
abdomen. In Megachile, general habit will bring the 
males within the precincts of their genus, as well as their 
largely dilated anterior tarsi in some of the species. 
A difficulty similar to what is found in the distinction 
between Andrena and Cilissa, arises in the separation of 
Chelosloma from Heriades, and which we shall again 
meet with in drawing the line between Anthophora and 
Saropoda . The difference can only be detected by ex¬ 
amining the trophi, but a pin and a little patience will 
elucidate the separation. The males in all but two 
species of Anthophora may be readily associated with 
their partners; but in these two the females are entirely 
