THE GROUND BEETLES. 



39 



bh. Hind coxae not separated; labrum not forked. 



c. Mandibles without a bristle-bearing puncture on the outer side; 



size large, 18 or more mm. Tribe III. Carabini, p. 44. 



cc. Mandibles each with a bristle-bearing puncture on the outer side; 

 smaller, not over 12 mm. Tribe V. Nebritni, p. 50. 



aa. Front coxal cavities closed behind. 



<l. Presternum prolonged and dilated, entirely concealing the mesu- 

 sternum ; seutellum invisible. Tribe I. Omophronini, p. 39. 



<1<L Prosternum not concealing the mesosternuni. 



e. Antennae free at base; body not pedunculate, the bases of* thorax 

 and elytra in contact; seutellum visible. 



Tribe IV. Elaphkini, p. 48. 

 ee. Antennae arising under a frontal plate; body pedunculate, the 

 bases of thorax and elytra remote; seutellum not visible; hind 

 coxae contiguous. Tribe VI. Scaritini, p. 53. 



Tribe I. OMOPHRONINI. 

 Antennas slender, inserted under a slight frontal margin, four 

 basal joints glabrous; mandibles with a bristle-bearing puncture on 

 outer side ; second joint of labial palpi with several seta* or bristle- 

 like hairs; body not pedunculate; mesosternuni covered by the 

 prolonged prosternum. The tribe is represented by the single 

 genus : 



I. Omophron Latr. 1802 (Gr., "savage-like.") 



Form oval, convex; seutellum invisible. The species occupy 

 holes in wet sand along the margins of streams, ponds and lakes. 

 They are also often 

 found under stones or 

 in holes between the 

 roots of plants along the 

 water's edge, and are 

 frequently caught in 

 minnow seines. By 

 throwing water over the 

 sand banks they can be 

 forced out and are then 

 easily captured, as they 

 do not fly. For detailed 

 papers on the genus see : 



Horn. — ' ' Synopsis of 

 m o phron," in 

 Trans, Amer. 

 Ent. Soc, III, 



1870, 71. Fig. 27. Omophron labiatum Fab. X 9. (After Forbes.) 



