On Aquatic Carnivorous Coleoptera or DytiscidcB. 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 erythro)>tervs, M.C. — Minus 

 regulariter ovalis, minus convexus, haud nitidus, niger, elytris fuscis, margine 

 externo late rufescente, antennis et tibiis anterioribus rufis, pedibus posterioribus 

 piceis ; supra undique crebrius reticulatus ; prothorace lateribus conspicue rotundatis. 

 Long. 92, lat. 5i m.m. 



The structure of the male feet is very remarkable in this species, the anterior 

 tarsi are much iacrassate and compressed, both the fourth and fifth joints being 

 stout, the first joint 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 from 

 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 cilise on each side, the 

 fifth joint of the middle foot is very elongate and its claws large. There is a 

 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 heneuth with remarkably large palettes ; wings of meta- 

 sternum only moderately large ; swimming legs moderately long and stout ; surface 

 conspicuously reticulate. 



Two European species. 



3 T 2 



