206 FAMILY TV. DYTISnn.l]. 



other insects. l)ut often u]nn] small inslies. and are sometimes very 

 troublesome in artitieial fish ponds, where they attack the young 

 and eat oflt' their fins. They also l"eed upoD dead animal matter of 

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



The larvae of the 

 DytiseidiP are also 

 aquatic and carnivo- 

 rous, and are known 



Fig. 105. Larva of l)y„s.-ui. , Af..-,- (•ums.o.k., ^^ "water tigerS. " 



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

 with a large o\al 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 fi'om any prey which they may capture. 

 These grubs remain in the water until full grown, when they seek 

 out some convenient place beiu^ath 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 ;^00 species of Dytiscida^ are known from the United 

 States. Of these 70, i-e])resenting 24 genera, ha\'e been taken in In- 

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

 srulptur-e presented l)y the Carabid;e 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 

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

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

 LeConte. — "An.alytical Table of the Species of Hydroporus 

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

 cies," m Proc. Acad. Nat. Sci. Phil., VII, 1855. 290-299. 

 JjtConle. — ''Synopsis of the Species of Colymbetes Inhabiting 

 America North of ?\lexico." iit Proc. Acad. Nat. Sci. Phil., 

 1862, 521-528. 

 Crotch. — "Revision of the Dytiscida^ of the ITnited States," in 



Trans. Amer. Kid. S.ic IV. 1878. 888-424. 

 Hharp'-Ou Acpiafic Carnivorons Coleoptera or DytiscidjB, i)i 



Trans. Royal Pnl)lin So:'.. 11. Ser. 2. 1882. 179-1003. 

 Horn. — ^Miscellaneous Notes and Shdrt Studies of North Amei-- 

 ican C'oleopteia. in Trans. Amer. Ku\. Soe., X, 1883, 276-284. 

 For convenience the family is lii'st divided into subfamilies aUd 

 tribes. 



