AMERICAN COLEOPTERA. 89 



TACIIIXITS Grav. 

 From tlicir superficial similarity the species of this genus are in 

 great confusion in most if not all collections, owing to the fact that 

 the characters which should be relied on for their separation, have 

 been lost sight of by our collectors. 



The sculpture is remarkably uniform, differing a very little with 

 each species, not sufficiently to be described, yet enough to enable a 

 mixed series to be separated with a very great degree of accuracy by 

 an experienced eye. In this way the sexes must be approximated, if 

 by any accident collections are in confusion. Color is of extremely 

 little value and should never be depended on. 



The characters made use of in the following tables are drawn 

 entirely iVdUi the variations in form of the last two ventral and the 

 terminal dorsal segments of the two sexes, but befurc giving the table 

 it will be necessary to enter into some explanation of the characters 

 so that they may be properly understood. 

 Male>i. — Anterior tarsi always dilated. 



The last ventral segment in all the species is deeply divided form- 

 ing processes {/arinise),oi' varying shape, frequently long, slender and 

 decurved, resembling somewhat the forceps of Forficula, often broader 

 in the form of triangular plates. The sixth segment varies also in 

 form and sculpture. In most species the hind margin is notched or 

 emarginate and the surface concave or impressed, the impression in 

 several instances extending on the fourth and fifth segments also. 

 The surface of this concavity in the sixth ventral is sometimes en- 

 tirely filled with very short and stout spinules among which dirt be- 

 comes entangled, so that Krichson and others have erroneously called 

 this a spongy space. In other species this spinous space is of more 

 limited extent and may be confined entirely to the middle of the 

 posterior margin, or entirely absent. In a few species there is no 

 concavity of the sixth ventral. 



The hind margin of the sixth ventral may be truncate or variously 

 emarginate and with a secondary emargination near the side. In the 

 first eleven species the margin is fimbriate with stiff, closely set spinules 

 forming a comb-like structure, the middle of the edge for a short 

 distance being usually without them. Four moderately long, slender 

 setae belong to this segment, two arising from the surface in the usual 

 position of the ambulatorial setae, while two others more distant arise 

 from the margin. In those species without the pectinate margin, the 



TRANS. AM EH. E.NT. SOC. VI. (13) JUNE, 1877. 



