206 FAMILY IV. llYTlSCIin/E. 



of her insects. Imt often upon small fishes, and are sometimes very 

 troublesome in artificial fish ponds, where they attack the young 

 and eat off their fins. They also feed upon dead animal matter of 

 any kind which finds its way into the water where they live. 



The larvge of the 

 Dytiscidae are also 

 aquatic and carnivo- 

 rous, and are known 



Fig. lOo. Larva of Dvtisnid. (After Cornstock.) , >? 



as water tigers. 



(Fig. 105.) In form they are elongate, cylindrical or fusiform, 

 with a large oval or rounded and. flattened head. The jaws or man- 

 dibles are sickle-shaped and hollow, so that they can easily hold 

 and suck the blood or juice from any prey which they may capture. 

 These grubs remain in the water until full grown, w r hen they seek 

 cut some convenient place beneath a board, stone or tuft of vegeta- 

 tion where, by the squirming motions of the body, a cell is formed 

 in which they undergo the pupal stage. The length of time neces- 

 sary for this transformation varies greatly with the species and the 

 season. 



Nearly 300 species of Dytiscidae are known from the United 

 States. Of these 70, representing 24 genera, have been taken in In- 

 diana. The family does not offer that diversity of color, form and 

 sculpture presented by the Carabida? and other families of terres- 

 trial beetles, hence the number of characters used for the separation 

 of genera and species is limited and the work, therefore, made more 

 difficult for the beginner. The classification is mainly that of Drs. 

 LeConte, Sharp and Horn and Mr. Crotch, in the following works: 



LeConte. "Analytical Table of the Species of Hydroporus 

 found in the United States, with Descriptions of New Spe- 

 cies." In Proc. Ac-ad. Nat. Sci. Phil.. VII, 1855, 290-299. 



LeConte. "Synopsis of the Species of Colynibetes Inhabiting 

 America North of Mexico," -in Proc. Acad. Nat. Sci. Phil.. 

 1862, 521-523. 



Crotch. "Revision of the Dytiscida 1 of the United States," in 

 Trans. Amer. Ent. Soc. IV. 1873. 383-424. 



Sharp. On Aquatic. Carnivorous Coleoptera or Dytiscida?. in 

 Trans. Royal Dublin Soc.. II. Ser. 2. 1882. 179-1003. 



Horn. Miscellaneous Notes and Short Studies of North Amer- 

 ican Coleoptera. in Tnins. Amer. Kut. Soc.. X, 1883, 276-284. 



For convenience the family is first divided into subfamilies and 

 tribes. 



