NORTH AMERICAN COLEOPTERA. 
161 
with fewer and weaker spines than the male, and the last dorsal 
segment is rounded at ajiex and more or less elongate. The males 
besides being narrower and more strongly armed on the femora, have 
the pygidium shorter and either truncate, arcuately emarginate, or 
acutely triangularly emarginate, but never rounded. The males of 
palmata have the anterior tarsi dilated, and the same sex of piscatrix 
has the first ventral segment excavated. 
All the species of Donacia are subaquatic in habit, frequenting 
either the pond lilies, on the broad leaves of which they may be seen 
from A{)ril to Septendier, or the rushes and sedges that grow in danqi 
places. 
In the following synoptic table several new names will be noted ; 
these are : 
cmcticornis Newn., which was formerly called lucida Lac., or in 
the check lists rugifrons Newn. 
pusilla Say, which antedates and replaces cuprea Ky. 
rufa Say, which antedates and replaces Kirbyi Lac. 
The scheme proposed is as follows : 
Head and thorax evidently pubescent above Group A. 
Head occasionally, thorax never pubescent. 
Elytra truncate at tip, or subtruncate. 
Form decidedly flattened ; mesosternum about as broad as each coxa. 
Group B. 
Form more convex; mesosternum narrower than the coxa Group C. 
Elytra rounded at tip, the sutural marsin sinuate posteriorly; form convex; 
mesosternum narrow Group D. 
Group A. 
Three species fall into this group which are not otherwise at all 
similar. It will be noted puhes^cens is the only species with pu- 
bescent elytra, and puhicollis the only one with the femora destitute 
of teeth or spines in both sexes. A badly rubbed specimen of hir- 
ticollis might be placed in the next group, from all the species of 
which it may be distinguished by the very small tooth of the femora, 
which is often reduced to a mere lump. The species are separated 
thus : 
Elytra without pubescence; posterior femora with a small tooth. ..liirticolli;S. 
Elytra without pubescence; posterior femora simple ptibicollis. 
Elytra evidently pubescent; posterior femora toothed |>iibesceii$$. 
TRANS. AM. ENT. .SOC. XVIII. 
( 21 ) 
.JULY, 1891. 
