AMERICAN COLEOPTERA. 103 



Facies. — Species of a genus and genera of a tribe have a greater 

 or less resemblance which affords to the practiced eye an easy guide to 

 position, but there are in many parts of the series such close repetitions 

 of form that this can not be relied on. Tetragonoderus and Bembi'dmm, 

 Patrohus and Nebria, Di/schirius and Apotomus, Cyclosomus and 

 Omophron, are instances of this mimicry. On the other hand allied 

 genera will be found presenting diversity of aspect and some may be 

 polymorphic as to their species, as Carabus and Ct/chrus. 



With this review of the separate parts of the body the preliminary 

 portion of this essay closes. I have purposely avoided citing many 

 instances of the occurrence of each character as the genera are unknown 

 to most of the students of our fauna and our native genera have been 

 cited when they answer the purpose. 



The Carabidie may be divided in the following manner into three 

 sub-families : 



Middle coxal cavities not entirely enclosed by the sterna, the epimcron 



of the mesosternum attaining the coxa. . . . CARABINE. 



Middle coxal cavities entirely enclosed by the sterna, the epimeron not 



attaining, the coxa. 



Head without antennal grooves beneath and with distinct supra-orbital 



setae. Ambulatorial setae of abdomen usually well developed. 



HAR PALING. 



Head with distinct usually long antennal grooves beneath and without 



distinct supra-orbital setae. Ambulatorial setae of abdomen feeble 



or wanting PSEUDOMORPHINJS. 



The only exceptions known' to me in the structure of the middle coxal 

 cavities is in MormoJjjve^ of which mention has already been made. The 

 z a3 n i n i and S i a g o n i n i have been considered exceptions but by care- 

 ful preparation of specimens I have found the coxal cavities as in the Harpa- 

 linae. In the proper place these matters will be found more fully discussed. 



Sub-Family CARABINjE. 

 . Middle coxal cavities partially closed by the sterna the intervening space 

 occupied by the mesosternal epimeron. Head with one or two supra- 

 orbital setigerous punctures. Sides of thorax usually with two setigerous 

 punctures. Anterior tibiae either entire, obliquely grooved or emarginate, 

 the spurs either both apical or with the inner more or less remote. 



The tribes of this sub-family contain a less number of genera than the 

 Harpalinae, but of such a specialized type as to make it necessary to separate 

 them to such an extent that many of the tribes contain but one genus. 



