132 NORTH AMERICAN 



rapidly in width ; border moderate ; surface rather closely and finely punc- 

 tate ; transverse carinae not cusped. Legs rather dark fusco-piceous, some- 

 what short and stout ; first joint of the posterior tarsi equal in length to twice 

 the second, joints two to four equal in length. Under surface black, shining. 

 Maxillary palpi having the first two joints pale testaceous, third joint darker. 



Male. — Unknown. 



Female. — Sixth ventral segment having the apex produced in th^ form of 

 an exceedingly broad triangle. 



Length 2.1-2.3 mm. 



Detroit, Michigan, 2 ; Ann Arbor, Michigan, 1. 



Division C. 



This, the concluding division of the genus Stenus proper, as here 

 considered, is composed of species very easily recognizable, "by the 

 absence of a distinct lateral border on the abdomen, when viewed 

 from above. 



The section was proposed by Erich son, and has been followed by 

 all authors who have treated the subject ; still discretion is necessary, 

 as the border is always present on the first segment to a greater or 

 less degree ; elsewhere, however, it is obsolete, being nothing more 

 than the fine suture along which the dorsal and ventral surfaces of 

 the segments are joined. There are rare cases where a slight border 

 is also apparent toward the bases of several segments after the first. 



The following scheme may assist in identifying our limited number 

 of species; they are all small and for the most part slender in outline, 

 with the abdomen cylindrical ; they generally have all the integu- 

 ments roughly and deeply sculptured. 



Punctures of elytra isolated and distinct, not coalescent. 



Robust, very convex, nearly cylindrical, densely pubescent, very coarsely 



punctate 112. gratiosus. 



Much more slender, depressed, very sparsely pubescent, finely punctate. 

 Elytral suture just perceptibly longer than the pronotum. New Hamp- 

 shire 113. monticola. 



Elytral suture nearly one-third longer than the pronotum. Lake Supe- 

 rior 114. curtus. 



Sculpture of elytra consisting of more or less coalescent punctures ; generally 

 very roughly, deeply, and tortuously channeled. 

 First joint of the posterior tarsi more than twice as long as the second. 



115. alacer. 

 First joint of the posterior tarsi distinctly less than twice as long as the 

 second. 



Transverse carinae of abdomen 4-cuspid 116. llirsiltllS. 



Transverse carinae tricuspid. 



