On Aquatic Carmvorous Coleoptera or Dytiscida. 525 
elongate and slender, and sinuate beneath : the female agrees with the male in the 
smooth shining upper surface. I have seen but two individuals of the species, which 
appears to be extremely closely allied to Agabus obsoletus (No. 730), but has the 
thorax rather smaller, and rather less continuous in outline with the elytra, the 
colour paler, and the elytra in the female smooth. 
North America, (Kansas). 801. 
735. Colymbetes erythropterus, Say, Agabus erythropterus, M.C.—Minus 
regulariter ovalis, minus convexus, haud nitidus, niger, elytris fuscis, margine 
externo late rufescente, antennis et tibtis anterioribus rufis, pedibus posterioribus 
piceis ; supra undique crebrius reticulatus ; prothorace lateribus conspicue rotundatis. 
Long. 93, lat. 52 m.m. 
The structure of the male feet is very remarkable in this species, the anterior 
tarsi are much incrassate and compressed, both the fourth and fifth jomts being 
stout, the tirst jot underneath has its larger portion bare and its apical one 
densely clothed with glandular hairs, while the hairs on the two following joints 
bear rather large palettes, the front claws are largely developed and peculiar, the 
anterior one being greatly thickened beneath, and so with a rounded outline, while 
its upper edge is nearly straight, the slender hinder one when looked at frem 
behind appears grooved ; both bear a small angular tooth at their extreme base : 
the three basal joints of the middle tarsi are clothed beneath in a similar manner 
to the front ones, and the fourth joint on middle and front feet seems to be hollow 
beneath, but to have the cavity clothed with dense short cilize on each side, the 
fifth joint of the middle foot is very elongate and its claws large. There isa 
remarkable sexual difference in the sculpture of the elytra ; in the male their surface 
is covered with well marked reticulations which form (very irregularly) quadrate 
meshes ; while in the female the basal portion of the elytra is densely covered with 
longitudinal scratches, which form very elongate slender meshes, while the sculpture 
at the apex is similar to that of the male. The male seems to be rather larger 
than the female. 
North America, (Lake Superior, Pennsylvania), 804. 
Group 17. 
Prosternal process flat, very finely or indistinctly margined ; male front tarsi much 
incrassate, and furnished beneath with remarkably large paleties; wings of meta- 
sternum only moderately large ; swimming legs moderately long and stout ; surface 
conspicuously reticulate. 
Two European species. 
