180 COLEOPTERA OF NORTH AMERICA. 



Sub-Family II.— ELATERIN^. 



The anteniife in this sub-family are widely separated, inserted 

 in small fovete under the margin of the front, before the eyes. 

 The mouth is usually anterior; the mandibles are small and re- 

 tracted, except in the last tribe, in which, too, are found the only 

 genera having the labrum connate with the front. The middle 

 coxae are always angulated externally, with a small, but distinct, 

 trochantin, so that the episterna are not cut off from the coxal 

 cavity. In a few genera of the last tribe the anterior and middle 

 coxae are conical. The tibiae are slender in all the genera. 



The tribes appear to be naturally arranged as follows : — 



Antennae received in deep pro.sternal grooves. Agrypnini. 



Antennae not received in prosternal grooves ; 



Meso- and metasterna connate. Chalcolepidiini. 



Mesosternal suture distinct (side pieces of metathorax narrow in our 

 tribes) ; 

 First joint of antennae very long. Hemikiiipini. 



First joint of antennae moderate ; 



Apex of mandibles obtuse or emarginate. Elaterini. 



Mandibles with the tip slender, prolonged, acute. Plastocerini. 



Tribe I.— AGR¥PiVI]Vl. 



These insects are easily recognized by the antenna received in 

 grooves excavated along the prosternal sutures; the mandibles 

 are emarginate at. tip, or toothed; the front flat or concave; the 

 mesosternum not, or but slightly, protuberant; the coxal plates 

 are gradually, but slightly, dilated internally; the tarsi in our 

 genera have the joints slightly inflated beneath, not furnished 

 with membranous lobes; the prosternal lobe is large; the an- 

 tennoe are serrate in our genera. The species are found under 

 bark of dead trees. 



Antennal grooves occupying the whole, or nearly the whole, of the pro- 

 sternal suture ; 



Third joint of the antennae smaller than the fourth. Agrypnus. 



Third joint of the antennae equal to the fourth. Adelocera. 



Antennal grooves much abbreviated behind ; 



Front tarsi received in grooves. Lacon. 



Front tarsal grooves wanting. Meristhus. 



Of Agrypnus two species are found in Texas; Adelocera is 

 found in our whole territory, and Lacon in the Southern States 

 and Kansas. 



