THE CLICK BEETLES. 713 



Subfamily II. ELATERINAE. 



The click beetles belonging to this subfamily have the antennas 

 widely separated and inserted in small pits before the eyes and 

 under the margin of the front; head usually horizontal, with the 

 mouth in front; mandibles small and retracted; middle coxa? with a 

 small but distinct trochantin ; tibia? slender in all the genera. The 

 subfamily is divided into five tribes, three of which are represented 

 in Indiana, while a single species of another probably occurs. 



KEY TO INDIANA TRIBES OF ELATERIN.E. 



. Antenna? in repose received in deep grooves on the under side of thorax. 

 (Fig. 272, 6.) Tribe I. AGKYPNINI, p. 713. 



aa. Antemuo not received in grooves on prosternum. 



6. Meso- and metasterna firmly united without visible suture ; size very 

 large. Tribe II. CHALCOLEPIDIINI, p. 716. 



66. Mesosternal suture distinct. 



c. First joint of antenna? very long. 



Tribe III. HEMIRHIPINI, p. 718. 



cc. First joint of antenna? moderate ; apex of mandibles obtuse or 

 einarginate. Tribe IV. ELATERINI, p. 718. 



Tribe I. AGRYPNINI. 



Medium sized elongate-oblong, subdepressed beetles, usually oc- 

 curring beneath the bark of dead trees. They are easily recog- 

 nized by the distinct antennal grooves lying alongside the prosternal 

 sutures. The base of under side of thorax is also deeply grooved 

 for the reception of the front femora. In front of these is often an 

 additional groove for the tarsi. When the three sets of grooves are 

 present the prosternum presents a very remarkable sculptured ap- 

 pearance. (Fig. 272, b and r.) The mandibles are emarginate or 

 toothed at tip ; antenna? serrate ; tarsal joints slightly dilated be- 

 neath but not lobed. Two of the four genera are represented in 

 Indiana. 



KEY TO INDIANA GENERA OF AGRYPNINI. 



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

 sternal suture (Fig. 272, 1>) ; third joint of antenna? equal to the 

 fourth. XIII. ADELOCERA. 



aa. Antennal grooves much abbreviated behind; front tarsi received in 

 grooves ; third joint of antenna? smaller than fourth. XIV. LACON. 



XIII. ADELOCERA Latr. 1829. (Gr., "invisible + horn.") 



The principal characters of this genus have been set forth under 

 the tribe heading and in the above key. Our species are coarsely 

 punctured above and beneath and have a portion or all of the upper 



