250 NATURAL ARRANGEMENT OP INSECTS. 



them and the rapacious tribes of quadrupeds and birds. 

 As among the Lamellirornes there are none of a car- 

 nivorous nature, so in the tribe before us there are none 

 which do not either wholly, or in part, live upon animal 

 substances, whether in a living or a decayed state. This, 

 therefore, is their primary distinction, — difficult, indeed, 

 to be traced in the aberrant groups, from the great vari- 

 ation of their structure, but decidedly marked in the 

 great majority, whether we regard their natural economy, 

 or their peculiar organisation. 



(22-1.) That this is a natural group, will be further 

 apparent by the arrangement of MacLeay : this acute 

 entomologist, looking to the formation of their larvae 

 alone, designates the genera Carahus and Dytiscus as 

 examples of his chilopodiform type ; so that, without 

 founding our arrangement upon isolated principles, ap- 

 plicable only to the annulose animals, we yet see that, 

 in this instance, it is in perfect conformity with his 

 general views. 



(225.) In order to give intelligible characters of this 

 or any other natural group, it is necessary to look chiefly 

 at the typical examples, where the pre-eminent charac- 

 ters are most developed. This remark is particularly 

 applicable to the group before us, which, although pal- 

 pable in three of its minor divisions, has not been suf- 

 ficiently studied in regard to the two ©thers. Confining 

 our attention, therefore, to the typical predacious beetles 

 represented by the Cicindelidce and the Carabidce, they 

 may be known at once by the length of their legs, and 

 the perfect developement of their tarsi, both of which 

 are formed for running upon the ground ; they are, in 

 fact, eminently cursorial : the mouth is armed with 

 strong jaws, and the antennse are linear or setaceous. 

 On looking to the aberrant groups, however, nearly all 

 these external characteristics disappear. The Dytiscidee 

 or water beetles, have a large depressed body, and short 

 thick feet, — the hinder pair being somewhat oar-shaped, 

 and calculated for swimming; in their setaceous antennae. 



