308 Journal New York Entomological Society. [Vol. xxvii. 



them readily. 1 In Donacia harrisi we would have a disturbing ele- 

 ment if placed in either of the two subgenera. However, this species 

 possesses a unique character not present in any other species and that 

 is the third antennal joint distinctly longer than the fourth in both 

 sexes. In all our other species the third antennal joint is mostly 

 shorter than or subequal to the third. The head is scarcely con- 

 stricted behind causing the less prominence of the eyes ; the posterior 

 femora of the male are armed with one large tooth and several small 

 teeth or denticles on the inner margin and the hind tibiae are feebly 

 angulated internally about one third from apex, which may also be 

 termed feebly emarginate with a few, feeble denticles or tubercles 

 within the emargination. The female has the posterior femora mutic 

 and the posterior tibiae are not emarginate or subangulate near apex 

 but have the inner side more or less distinctly tuberculate, the tubercles 

 at most small. The posterior femora of both sexes are robust but 

 rather feebly clavate. The first ventral segment is a little longer than 

 the metasternum in both sexes and about as long as the next three 

 ventral segments. 



The principal characters separating the three subgenera are : 



i. Sutural margin of elytra entire to apex Donacia 



Sutural margin of elytra distinctly sinuate near apex 2 



2. Third antennal joint longer than fourth; head feebly constricted behind the 

 eyes ; posterior femora of male with a moderately large, acute tooth and 

 a variable number of denticles along the inner margin, posterior tibiae 

 feebly emarginate one third from apex, feebly tuberculate within the 

 emargination ; posterior femora of female mutic, posterior tibiae not 

 emarginate near apex but feebly tuberculate near the inner margin. 

 Vaginal plates of the female equal, subtruncate or feebly emarginate at 

 apex, both plates of equal size, that is, the lower one not longer and not 



produced into a sharp point at middle Poecilocera 



Third antennal joint shorter than fourth ; head strongly constricted behind 

 the eyes ; posterior femora of male with a single distinct tooth and no 

 denticles; posterior tibiae not emarginate near apex and without denticles 

 in either sex. Vaginal plates of the female subequal ; the upper one 

 narrower and shorter than the lower one, the latter produced at middle 

 of apex into a more or less sharp point, the edges either very finely or 

 coarsely serrated Plateumaris 



1 Mr. Leng in his revision attributes this character to distincta also but I 

 am unable to see it in any of the numerous specimens which I have examined. 



