194 Trans. Acad. Sct. 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. 
LOWS. coccccccecnavecsccescesisvecvescssscvscccscs cesscecE MOMS 1. SDe 
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 jferrugineus, which is represented only 
by the male, do not lie altogether in the direction of the 
sexual differences as observed in rubens, and there seems to 
be but little doubt of their validity. 
Pycnorus 0. 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 
