THE CKAWLINO WATEK BEETLES. 



203 



they may often be noted crawling slowly over the partially decayed 

 aquatic plants, especially algae. On account of their feeble swim- 

 ming powers they may be easily captured by raking the mass of 

 vegetable matter onto the bank, when the beetles, on crawling out 

 to regain the water, may be secured. The name of the family is 

 derived from the Greek and means "sailing the sea," or "covered 

 with water.'" 



The larvae of the Haliplida? live in the same places as the adults. 

 They are composed of slender segments, each, except the head, 

 being furnished on the back with fleshy lobes, bearing spiny tips, 

 while the last segment is extended into a long tapering appendage. 



The principal paper, including descriptions of the North Ameri- 

 can species of this family, is by 



Crotch.- — "Revision of the Dytiscidae of the United States," in 

 Trans. Amer. Ent. Soc. IV, 1873. 333-385. 



The North American species are divided among three genera, 

 two of which are represented in Indiana. 



KEY TO INDIANA GENERA OF HALLPLLDyE. 



a. Terminal joint of palpi small, awl-shaped; intervals of elytra punctate; 

 thorax without black spots at base. I. Haliplus. 



aa. Terminal joint of palpi conical, longer than the third; intervals of ely- 

 tra without punctures ; thorax with two small round impressed black 

 spots at base. II. Cnemjdotus. 



I. Haliplus Latr. 1806. (Gr., "the sea + sail.") 



Of the ten species of this genus known from the United States, 

 six have been taken in Indiana, while another may occur. 



KEY TO INDIANA SPECIES OF HALIPLUS. 



a. Thorax without a basal impression. 



b. Prosternum margined at sides ; elytral punctures deeper at base than 

 apex. 



c. A distinct black spot on middle of front margin of thorax. 



383. teiopsis. 



go. Thorax, without black spot, sometimes slightly darker at apex. 

 d. Elytra not sinuate near apex. 



c. Spots of elytra distinct ; size larger, 3.5-4 mm. fascia tus. 

 ee. Spots more or less confluent ; size smaller. 2.5 mm. 



384. LEwisn. 



<M. Elytra distinctly sinuate near apex ; spots often slightly con- 

 nected but not confluent. 3S5. borealis. 

 hh. Prosternum flat, not margined at sides ; elytral punctures not deeper 

 at base than apex; elytra dull brownish-yellow with elongate black 

 spots. 38G. CRIBARIUS. 



