136 
BRITISH BEES. 
they may be separated, for the sake of convenience, and 
as descending grades whereby to arrive with greater 
facility at their genera, jnst as the species of the latter 
are also sometimes grouped, that they may be reached 
with greater ease. These subdivisions of families have 
no analogy with the varieties which species occasionally 
throw off, although they may be as irregular in their 
occurrence; that is to say, in the association of a group 
of families arranged in their series of most proximate 
affinities, the first may present subdivisions, others, in 
irregular occurrence, may not require them,—just as in 
the species of a genus, arranged also in the series of 
their closest resemblances, one will present a stringent 
adherence to the specific type, or all may do so, or all 
or some may have a tendency to vary. Groupings of 
species are, however, of a less natural character usually 
than are those of families, and generally are artificial, 
being capriciously made to break down long genera, that 
the required species may be more readily arrived at. 
The characters which group families differ inter se. 
Thus in the Order Hymenoptera , the family of the bees 
is essentially framed upon their most distinguishing 
peculiarity—the tongue,—which in other families be¬ 
comes of secondary importance. In some the neuration 
of the wings, their mode of folding, the form of the 
eyes, conjunctively with other peculiarities of general 
structure, etc. etc., which point to the differences in the 
economy that accompany all these, have successively the 
same prominent position which the trophi take in the 
family of the bees. 
I have already recently alluded to the relations of 
affinity and analogy, and it is desirable that some notion 
of the meaning and bearing of these terms should be 
