I.— INTRODUCTION 



In this county very little attention has been devoted to the biology 

 of the water beetles of the family Hydrophilidse, and there exists a woe- 

 ful lack of knowledge concerning the immature stages. A general sur- 

 vey of the aquatic members of the family was begun by the author in 

 the spring of 1914 and has been continued until the present time. 

 Primarily the New York State species, especially those occurring in the 

 vicinity of Ithaca, have been dealt with but the collection of the United 

 States National Museum (which consists mostly of European material) 

 has also been examined. All the genera here discussed have been reared 

 by the author. Some specimens of the genus Hydrous were furnished 

 through the courtesy of Dr. Robert Matheson of Cornell University. 

 Throughout this paper the classification as given by the European 

 authors has been maintained as far as advisable, the grouping in use 

 in this country not having been influenced by the recent work of foreign 

 authors. 



For help toward the completion of this paper, I am greatly indebted 

 to the following men: Dr. J. G. Needham, who personally directed this 

 work; Mr. F. E. Wintersteiner, who so willingly helped in the identifica- 

 tion of the adults; Dr. Adam Boving of the United States National 

 Museum, who gave valuable suggestions in regard to the larvae, descrip- 

 tions and drawings; and Dr. L. O. Howard, who kindly placed the 

 specimens of the United States National Museum at my disposal. 



A set of the material upon which this paper is based is deposited in 

 The American Museum of Natural History. 



Historical 



The Hydrophilidse as a distinct group was first recognized by Latreille 1 

 when, in 1804, he applied the name Sphseridiota to this family. The 

 earliest data found concerning the biology pertain to the genera Hydrous 

 and Hydrophilus. This was presented respectively by Frisch in 1721 

 and Roesel in 1749. Until the middle of the nineteenth century very 

 little was added; and it was not until Schiodte's Monograph in 1861 

 that any collected work of note appeared. 



The little work that has been done in this country upon the natural 

 history of this group of beetles consists only of scattered observations 

 on the larger species. Life histories of American forms have been con- 



iLatreille, 1804, Hist. Nat. Crust. Ins., X, Ann. XII, p. 48. 



3 



