COI.EOPTERA. 155 



slender, tarsi slender, third joint of tlie posterior less than twice as long as 

 tlie two preceding together. 



M(tle. — Sixth ventral segment broadly and roundly emarginate in its 

 middle three-fifths at apex, edge of the emargination strongly reflexed and 

 densely fimbriate, paler in color ; the reflexed portion of the edge does not 

 occu^jy the entire emargination, but abruptly leaves a small portion of the 

 curve at the ends with the edge not modified. Seventh segment extremely 

 deeply impressed in the middle four-fifths, sides of the impression in the 

 form of very thin laminae projecting and acutely angulate posteriorly, where 

 they converge toward each other, arching far over the emargination. Eighth 

 segment acutely rounded behind, longitudinally and somewhat sliglitly im- 

 pressed along the middle of its under surface. 



Female. — Sixth segment very broadly and evenly rounded behind through- 

 out ; seventh very much narrower, acutely rounded behind. 



Length 3.2-3.5 mm. Male smaller than the female. 



Nebraska, 3. 



It is almost impossible to describe the wonderful sexual characters 

 of" the male so as to convey an entirely lucid idea to one who has 

 never seen the structure in nature. This species is distinct in its 

 very marked contrasts of color, the abdomen being very black, and 

 also by tlie peculiar structure of tlie antennae, in which the second 

 joint is as long as the third ; in addition to these differences there is 

 a complete absence of the long coarse setae which bristle upon the 

 pronotum and elytra of most of the others. 



2. A. spliaBricollis (Say). — Form ratlier more slender than in bicolor. 

 Color of head dark piceo-testaceous ; pronotum slightly paler ; elytra nearly 

 as dark as the head ; abdomen dark piceous above, piceo-testaceous beneath ; 

 metasternum much darker than the prosternuni ; legs uniform throughout, 

 very pale testaceous ; antennae pale testaceous at base, becoming deeply in- 

 fuscate toward the tip. Pubescence in the form of stiff erect coarse setae, 

 piceous-black in color and very sparse. Head moderate ; eyes very small, 

 slightly prominent, situated at more than twice their length in advance of 

 the posterior angles ; sides behind them slightly convergent and arcuate ; 

 interocular surface polished, impunctate ; supra-antennal tuberculations 

 long, strong, parallel, each having a foveate impressed puncture at its 

 posterior extremity; antennae much longer than the head and prothorax 

 together, rather slender, second joint much shorter than the third. Pro- 

 thorax widest at the apical angles where it is as wide as long ; sides thence 

 very feebly convergent posteriorly and very feebly arcuate ; base transverse 

 and very feebly sinuate in the middle, apex bioadly and strongly arcuate ; 

 surface very convex, impunctate and highly polished. Elytra at base 

 slightly wider than the prothorax ; sides slightly divergent and feebly 

 arcuate ; together broadly and extremely feebly emarginate behind, almost 

 transversely truncate ; suture and scutellum together distinctly longer than 

 the pronotum ; disk highly polished, impunctate except a row of very feeble 

 distant punctures near the exterior edges. First abdominal segment as wide 



