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, just 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 



