March, 1913-] ShERMAN : HaBITS OF THE DyTISCID.E. 43 



SOME HABITS OF THE DYTISCIDiE.* 



By John D. Sherman, Jr., 

 Brooklyn, N. Y. 



The animal fauna of the water is said to be largely controlled by 

 the character of the water bottom. 



The Dytiscidse, according to my experience, do not like very 

 muddy bottoms. A few of our commonest species do occur in such 

 bottoms, and in abundance, e. g., Hydrovatus cuspidafus Germ, and 

 Ccclambus incrqitalis Fabr. 



But the number of these species is small, and ponds and brooks of 

 the most promising appearance otherwise, but with very muddy 

 bottoms, are usually very disappointing when you are looking for 

 Dytiscidcc. These beetles prefer for their home bodies of compar- 

 atively clean live water, either spring-fed ponds or running brooks, 

 where the bottom is at least moderately clean or sandy. 



The presence of some vegetation, preferably small plants— espe- 

 cially those of a filamentous character, or submerged roots — is indis- 

 pensable. 



The almost absolutely clear mountain or forest lakes of the Lake 

 Superior region contain little plant life at their borders, a fact which 

 has been attributed, in the case of the larger lakes, to their greater 

 exposure to the ice. They apparently contain few if any beetles. 

 In the White Mountains of New Hampshire within a few miles of 

 each other are five small " lakes," of approximately the same size 

 at about the same elevation: the twin Carter Lakes, 3,150 feet high. 

 Hermit Lake and Glen Lake in Tuckerman's Ravine, 3,700 feet, and 

 Spaulding Lake in the Great Gulf, 4,150 feet. All of these except 

 Hermit Lake are very clear and practically without either vegetation 

 or beetles. Hermit Lake is rich in both, while Glen Lake, only a 

 quarter of a mile distant, contains neither. 



If the water is polluted, as for example by the presence of carrion, 

 the Hydrophilidae take precedence over the Dytiscidse. On the other 

 hand the presence of decomposing vegetable matter, such as dead and 



* The new names suggested in this paper for certain well known species 

 of Hydroporus will be more fully explained in a later paper, together with 

 other notes and descriptions of new species. 



