THE PREDACEOUS DIVING BEETLES. 



235 



rows of disks on under side. The elytra of female are either smooth 

 or rough, with miouce tubercles. Two species are known from In- 

 diana. 



460 (1498). Geaphoderes liberus Say, Journ. Phil. Acad. Nat. ScL, V, 



1825, 160; ibid. II, 271. 

 Slightly obovate, subdepressed. Head and thorax dull reddish-yellow, 

 the latter sometimes piceous at base ; elytra blackish-brown, with numerous 

 fine yellow vermiculate marks, these sometimes forming a yellowish mar- 

 gin; under surface reddish-brown, the legs paler. Elytra each with two 

 rows of indistinct dorsal punctures. Length 11.5-12 mm. 



Putnam and Lawrence counties; frequent in woodland ponds. 

 August 7- Aug ust 12. 



461 (1499). Graphoderes fascicollis Harr., N. Eng. Far., VII, 1828, 156. 

 Broadly ovate, subconvex. Head with occiput and an M-like mark 



black ; thorax dull yellow with a rather broad black bar on front and hind 

 margins; elytra blackish, thickly marked with dull yellow dots, the mar- 

 gins and a very narrow sutural line yellow ; under surface dull brownish- 

 yellow. Length 13.5-14.5 mm. 



Lake and Marion counties; scarce. March 23-May 27. This 

 species is said by Sharp to be distinguished from the European G. 

 cinereus Linn, by the male having fewer disks on the front and 

 middle tarsi. In one male from Pine, Indiana, the middle tarsi are 

 not at all dilated. 



Tribe IV. CYBISTRINI. 



This tribe is represented in the United States by a small number 

 of large species belonging to the single genus Cybister. They have 

 the spiracles very small ; hind legs broad and powerful ; their tibia? 

 short and broad, with the lower one of the two apical spurs dilated ; 

 hind claws very unequal, the inner being obsolete or wanting in our 

 species. The front tarsi of the males have joints 1-3 dilated into a 

 large circular disk bearing four rows of equal-sized cupules. In the 

 hollows behind the hind coxa? of the males are four or five deep 

 ridges which, when rubbed by a ridge on the under side of the fe- 

 mur, form a stridulating organ. 



XXIY. Cybister Esch. 1833. (Gr., ' ' a tumbler or diver. ") 



This genus is considered as representing the highest and most 

 completely developed form of Dytiscidre. One of the five species 

 known from the United States occurs in Indiana. 



