404 The American Naturalist. 
with metallic green. The length is about half an inch. The antenne — 
and legs are comparatively long, and the variation in the length of the 
joints of the one and in the spinous processes which adorn the other 
afford the most convenient characters, combined with the form of the 
elytral apices, for the separation of the species. They may be known 
as follows 
Prothorax not tuberculate, scarcely punctulate ; 
Third joint of antennz little, if any, larger than 
second ; 
Elytra squarely truncate, lucida. 
Third joint of antenne at least twice as long as í 
second ; 
Elytra squarely truncate, palmata. 
Elytra more convex, subtruncate, piscatnix. 
Prothorax not tuberculate, coarsely, densely punctate ; 
Third joint of antennz little longer than second ; z 
Elytra squarely truncate, subtilis. 
Prothorax evidently tuberculate, scarcely punctate ; 
Third joint of antennz little longer than second ; 
Elytra more convex, subtruncate, tuberculata. 
In addition to the above, the sexual characters assist in separating : 
the species. All the males have the last dorsal segment, called the 
pygidium or podex, short and truncate; the females have the sam” 
part longer and rounded at apex. The male of /ucéda has the posterior 
femora spinose, often armed with two or three spines; the female has A 
but one spine. The sexes of panata and piscatrix differ similarly 10 
the femora; the male pa/mata is further distinguished by 4 dilation 
of the first joint of the anterior tarsi, and the male of piscainix yy : 
excavation of the first ventral segment. The sexes of subtilis : 
but little ; both have the posterior femora unidentate. The male of 
tuberculata has but one spine, but the female is without any. x 
From the results of last season’s collecting I am satisfied that o 
above-described species affect different aquatic or subaquatic plants ; o 
the first three appertaining to the water-lilies, sud#lis to the pers 
growing at the pond margin, and ‘¢uderculata to the Sagittaria. = a 
evidence I have is as follows: Our collections were made principally 
at Britton’s ice pond, at the small pond on top of T A ee 
at Butler’s or Galloway’s pond near Garretson station. In Lee 
the yellow water-lily grows abundantly, mingled with the 
lily, but only at Butler’s pond do gradually shelving banks ator 
odt Hill, amd 
