COI.EOPTERA. 85 



than the width of head, black, slender, club distinct ; joints three, four, and 

 five decreasing very uniformly in length, but with excessive slowness, sixth 

 and seventh abruptly shorter, equal in length, the latter much thicker, 

 eighth slightly broader than long, last joint as long as the ninth and tenth 

 together, much thicker ; maxillary palpi rather short and slender, dark red- 

 dish-black throughout, Prothorax widest at the middle, where it is three- 

 fourths as wide as the head, and very slightly narrower than long ; sides 

 thence moderately convergent posteriorly and nearly straight ; anterior mar- 

 gin slightly shorter and more arcuate than the posterior ; surface nearly 

 evenly convex, finely, deeply, very closely, evenly, but somewhat confusedly 

 punctate, interspaces distinctly granulate; carialiculation extremely narrow 

 and indistinct, beginning at the middle and extending nearly to the base. 

 Elytra at base as wide as the head ; sides very feebly divergent posteriorly, 

 very slightly longer than the width at base, very feebly arcuate ; broadly 

 and somewhat feebly emarginate behind; suture just perceptibly longer 

 than the pronotum ; surface evenly and moderately convex, rather coarsely, 

 very closely, and somewhat confusedly punctate, interspaces coarsely granu- 

 late. First three abdominal segments sub-equal in width, as wide as the 

 contiguous elytra ; surface not strongly convex, closely, evenly, and coarsely 

 punctulate ; transverse carinae unieuspid, cusp very long, strong, becoming 

 finely acuminate ; there are also slight traces of lateral, rudimentary cusps 

 on some of the segments. Legs moderate in length and rather slender, dark 

 rufous above, paler beneath, tarsi darker; first joint of the posterior tarsi 

 one-half as long again as the second, three-fifths as long as the last, joints 

 two to four uniformly and very gradually decreasing in length. 



Male. — Posterior edge of the fifth ventral segment very feebly emarginate 

 in its middle fourth, emargination evenly rounded and just perceptible, 

 contiguous surface feebly flattened ; sixth segment sinuate at apex, sinus as 

 broad as the apices and equal to them in curvature, evenly rounded, some- 

 what more than three times as wide as deep. 



Female. — Sixth segment evenly rounded behind. 



Length 1.7 mm. 



Detroit, Michigan, 1; Cambridge, Massachusetts, 13. 

 The slender graceful form of this species, the most minute of the 

 genus, will readily distinguish it from the two preceding ones. 



Subdivision y. 



Prothorax not canaliculated. Elytra! sculpture as in subdivision j3. 



In order to tell whether the prothorax is canaliculated or not, the 

 insect should be held in such a way that the light may pass very 

 obliquely or tangentially across the highest point of the pronotum, 

 and perpendicularly to the longitudinal axis. If there be a deeply 

 impressed or excavated channel, it will, of course, be evident without 

 this test, but if, when held in the position above described, there be 

 no sign of even a narrow longitudinal shade, the pronotum will be 



