1G6 COLEOPTERA OF NORTH AMERICA. 



Presternum moderate, sutures double, straight or concave ; 



Tarsi not lobed beneath. Elateres. 



Third joint of tarsi lobed. Physoehini. 



Fourth joint of tarsi lobed. Monocrepidii. 



Second and third joints of tarsi with long lobes. Dicrepidii. 



Margin of the front not elevated. Ludii. 



Group I.— Cardiophori. 



The species are usually small, and convex in form, remarkably 

 distinguished by the prosternal spine being truncate behind, and 

 fitting like a wedge into the mesosternum ; the scutellum is cordi- 

 form ; the front is margined, but not concave ; the coxal plates 

 are suddenly dilated inwards. 



Several species of Cardiophorus represent this group in every 

 part of our country. 



Group II.— Cryptohypni. 



This group contains only small species, and is easily known by 

 the margined front, the suddenly dilated coxal plates, and the 

 broad prosternum, with the sutures single, and convex outwards ; 

 the coxal plates are scarcely toothed at the insertion of the 

 thighs; the tarsi are filiform. 



Cryptohypnus is generally diffused ; (Edostethus contains but 

 one species from the Atlantic district. 



Claws simple ; tarsi moderate, clothed with stiff hairs. Cryptohypnus. 

 Claws with a tooth at the middle ; tarsi long, pubescent. GSdostethus. 



Group III.— Elateres. 



In this group are species having the front convex and mar- 

 gined ; the thorax always narrowed in front ; the prosternum 

 not very wide, with the sutures distinctly double, and sometimes 

 excavated in front, straight or concave outwards; the posterior 

 coxal plates narrow externally, suddenly dilated internally, and 

 toothed at the origin of the thighs ; the tarsi not dilated or lobed 

 (the anterior ones in Blauta very slightly so), and the claws entire. 



Our genera are : — 



Prosternal sutures excavated in front ; 



Tarsi spongy beneath, the anterior ones slightly lobed. Blauta. 



Tarsi ciliate beneath, entirely simple. Elater. 

 Prosternal sutures not excavated in front ; 



Third joint of antennae longer than the second. Drasterics. 



Second and third joints of antennae small, equal. Megapexthes. 



