IDEA OP THE SUPERIOR GROUPS. 595 



The division immediately above a genus is usually called a family 

 It is peculiar to the natural system, and by this only is it called forth 

 Linnaeus and Fabricius, who formed artificial classifications, had no 

 families. 



The characters which distinguish the families are derived not only 

 from their resemblances in structure in general, but also frequently 

 from their economy. Thus the allied families of the Carabodea and 

 Hydrocantharides, which both live upon prey, are distinguished, as 

 well from their dwelling-place, and a very definite and easily recog- 

 nisable form of the body, and also by a very marked difference in the 

 structure of their posterior legs, whereas the organs of the mouth and 

 the antennae agree in the types. Were we to deduce the characters of 

 families from such relations, it could be defined only as one of resem- 

 blance ; in the similar structure of certain parts in several genera lie 

 the characters of a family. 



333. 



We sometimes also remark within the boundaries of a family, espe- 

 cially of a very comprehensive one, subdivisions, which bear the same 

 relation to the families as do the subdivisions of a genus to the latter. 

 Such groups have been indeed called sub-families. They are as useful 

 for the easier discovery of the genera, as the former for facilitating the 

 discovery of the species, and they are therefore more artificial than natural 

 groups. But it depends much upon their mode of division, for this 

 does not admit of being said of the sub-families of the large family of 

 the Ichneumonodea, and as little of many others. For the sake of an 

 example, we may be allowed to state that those three sub-families differ 

 in the structure of their palpi. The genuine Ichneumonodea have five- 

 jointed maxillary palpi, and four-jointed labial palpi ; the Braconodea 

 five-jointed maxillary and three-jointed labial palpi ; the Bassina six- 

 jointed maxillary and four-jointed labial palpi. Similar groups, founded 

 upon analogous relations, are found in the families of the Carabodea, 

 Lamellicornia, Rhynchophora, Vespacea, Apiaria, Muscaria, &c. 



334. 



The chief group above the family is the order ; it does not so much 

 depend upon a similarity of individual parts, as upon the entire body, 

 for instance, whether the thorax be divided in its three segments, or 

 whether these are closely jointed together ; upon the form and structure 



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