On Aquatic Carnivorous Coleoptera or Dytiscide. 637 
Mas, nitidus, elytris apicem versus externe parce subtiliter punctatis. 
Fem., minus nitida, prothorace versus latera rugoso-punctato, elytris versus basin 
externe crebrius minute punctulatis, ad apicem fortiter parciusque punctatis. 
In the male the small palettes of the front tarsi are well developed while those on 
the middle feet are minute and of a spongy appearance. The sexual differences of 
sculpture are not striking, and there is apparently only one form of female. 
This species and Dytiscus hybridus have the outline of the thorax and elytra 
more completely continuous than in any of the other allies, and the elytra are less 
sinuate at the apex. In D. habilis the broad yellow margins of the short thorax 
reduce the middle patch of dark colour to a transverse band ; beneath the thorax is 
yellow with the prosternal process blackish, the metasternum in the middle and the 
coxal processes are blackish, the large coxz being ferruginous ; the ventral segments 
are pitchy ferruginous, with indistinct black fascize. 
I have observed very little variation in this species. 
Mexico. 937. 
987. Dytiscus hybridus, Aubé, M.C.—Subtus piceus, supra nigricans, prothorace 
ad latera late, ad marginem anteriorem obsolete, flavo-marginato, elytris margine 
flavo ad apicem parum dilatato et disintegrato, antennis pedibusque quatuor 
anterioribus rufis ; angustulus, eequaliter transversim convexus; pedibus posterioribus 
brevibus, robustis ; prosterni processu angusto, sat elongato, apice minute recurvo ; 
coxarum processubus parum divergentibus, rotundatis. Long. 27, lat. 14 m.m. 
Mas, nitidus, elytris ad apicem perparum punctatis. 
Fem., sat nitida, prothorace versus latera plus minusve punctato, elytris versus 
basin externe minute punctulatis, versus apicem externe sparsim punctatis. 
The male has the small palettes on the front tarsi largely developed and of equal 
size; those on the middle feet are also well developed and are placed so as to leave 
a narrow, bare, longitudinal space along the middle. The female departs but little 
from the male, but its sculpture is variable, when most developed the punctures of 
the thorax are connected (or rugose) and the minute punctures on the base of the 
elytra are numerous and distinct ; when most diminished, the thoracic punctures are 
but little connected mater se, and the basal elytral punctures are scarcely to be 
detected. 
This species has the superficial appearance ofa species of Cybister on account of its 
short thick hind legs, its continuous outline, and rather broad and distinct yellow 
lateral band. Except in the sculpture of the females I have observed extremely little 
variation. I consider it the most highly developed species of the genus, 
Eastern North America. (Massachusetts ; Pennsylvania, Kansas, Illinois, sec. Crotch). 938. 
4N2 
