194 Trans. Acad. Sci. of St. Louis. 



the secondary sexual characters comparatively feeble but of the same 

 type as those of ferrugineus, the fifth ventral having a feeble, very 

 narrow longitudinal impression along the middle, gradually becoming 

 extinct before the middle of the length and not more than a tenth or 

 twelfth as wide as the segment, the posterior margin transversely trun- 

 cate, with a very minute feeble sinus at the posterior end of the impres- 

 sion; sixth segment having a very narrow deep and angular notch, 

 nearly three times as deep as wide. Length 2.9 mm.; width 0.68 mm. 

 Iowa rabens n. sp. 



A female from Iowa, apparently belongs to the male 

 described as rubens above, but shows that the sexual differ- 

 ences in general form of the body are very marked, the head 

 being much smaller in the female and only just visibly wider 

 than the prothorax, and the abdomen is parallel or nearly so 

 and distinctly more slender. Luridus and ochrinus are at 

 present represented by the female alone, but the divergencies 

 of these species from ferrugineus, which is represented only 

 by the male, do not lie altogether in the direction of the 

 sexual differences as observed in riibens, and there seems to 

 be but little doubt of their validity. 



Pycnorus n. gen. 



The species of this genus are few in number, widely dis- 

 tributed over nearly the entire country, except perhaps the 

 northern Pacific coast, and may be distinguished from Orus 

 by their stouter form, shorter and stouter tarsi, the anterior 

 more strongly dilated as a rule, more widely separated and 

 stronger gular sutures, by the short and broadly truncate 

 labrum, and, finally and more particularly, by the obliterated 

 anterior thoracic angles. From Leucorus they are still more 

 readily distinguished by this last character, as well as by the 

 larger, truncate and bidenticulate to virtually edentate labrum 

 of that genus. The male sexual characters are distinctive of 

 the genus, as may be seen below under the description of the 

 type species. The three forms known to me may be thus 

 outlined: — 



Form moderately stout, parallel, convex, shining, black throughout, the legs 

 piceous with the tarsi somewhat paler ; head minutely, not densely 



