56 BROOKLYN MUSEUM SCIENCE BULLETIN 3. 3. 
Prothorax very variable in form; anterior angles distinct, rarely 
somewhat broadly rounded; basal margin straight or arcuate. 
Elytra variable in form, generally not covering entirely the last 
abdominal segment, depressed or convex; apices truncate or emarginate, 
the angles are not or very rarely feebly prolonged; serial punctures in 
single rows; lateral margin not explanate near apex. 
Body below very densely or sparsely pubescent; pubescent spot 
near anterior coxae present or absent; first abdominal segment variable in 
length, shorter or as long or longer than the following segments ; posterior 
femora very variable but generally distinctly clavate and either short 
or very long; tarsi more or less dilated, spongy below; third joint deeply 
bilobed, as long or longer and never much smaller than second; claw- 
joint short, rarely as long as the two preceding joints, claws slightly 
appendiculate at base. The males have the last ventral segment truncate 
and more or less deeply impressed at middle of apex. 
The genus Donacia is divisible into three subgenera which will be 
recognized by the following key: 
Key to Subgenera. 
1. Sutural margin of elytra sinuate near apex; ocular orbits 
absent; first ventral segment of abdomen generally about 
as long as the three following segments 2. 
Sutural margin of elytra straight to apex; ocular orbits dis- 
tinct; ^ first ventral segment of abdomen about as long or 
slightly longer than the four following segments; elytral 
apices truncate, emarginate or rounded; third antennal 
joint subequal or shorter than the fourth; vaginal plates of 
females variable but apparently never serrate at apex and 
generally equal in length subg. Donacia. 
2. Elytral apices truncate or more or less distinctly emarginate; 
head not constricted behind the eyes; tempora obsolete; 
posterior tibiae serrate or denticulate internally in both 
sexes; male posterior femora armed below with two teeth, 
the aaterior one small, and a number of more or less distinct 
denticles along the lower edge, female posterior femora 
unarmed; third antennal joint longer than fourth in both 
sexes; vaginal plates of female equal in size, truncate or 
more or less distinctly emarginate at apex and not serrate . subg. Poecilocera. 
Elytral apices more or less rounded; head more or less deeply 
constricted behind the eyes; tempora distinct; posterior 
tibiae not serrate internally; posterior femora of male and 
female armed with one tooth only, which is sometimes 
^ In ruja Say {tuberculata Lac.) the ocular orbits are rather indistinct and scarcely 
visible in some specimens. 
