116 COLEOPTERA OF NORTH AMERICA. 



the palpi are short. The other characters are still variable, and 

 will furnish occasion for the division into tribes. 



Head not entirely retractile ; presternum not lobed in front ; antennse ser- 

 rate, with the first and second joints not enlarged. Lakini. 



Head retractile, protected by a prosternal lobe ; antennse short, first and 

 second joints enlarged. Paknini. 



Tribe I.— LARINI. 



The only representative known to rne is Lara avara Lee, from 

 California, an elongate, blackish insect, finely pubescent, with the 

 elytra punctured in rows, impressed behind the base, and the 

 thorax strongly narrowed in front, somewhat uneven; the antennas 

 are distant from each other, and what remains of them indicates 

 them to be serrate, and not irregular or short; the clypeal suture 

 is distinct ; the head is not protected beneath by a lobe of the 

 prosternurn ; the anterior coxae are somewhat prominent, the tro- 

 chantin large, free, and very distinct; the prosternal process is 

 narrow ; the mesosternum is prominent, deeply excavated ; the 

 middle coxa? are widely separated, and have distinct trochantin ; 

 the side pieces of the metathorax are narrow, the epimera slightly 

 visible behind; the epipleurae are narrow, and continue to the 

 apex. 



Tribe II.— PARNINI. 



The head is capable of being retracted, and is then protected 

 beneath by the prosternurn, which is lobed in front; the antennas 

 are inserted on the front, distant and free at the margin of the 

 eyes in Lutrochus, approximate and at the inner extremity of 

 transverse grooves, and remote from the eyes, in the other two 

 genera; they are short, 11-jointed, and more or less irregular in 

 form. The anterior coxae are not prominent, the trochantin small, 

 connate with sternum ; the prosternal process is wide ; the meso- 

 sternum broad, emarginate, the middle coxae with trochantin ; the 

 side pieces of the metathorax wide, with the epimera not visible, 

 except in Lutrochus, where they are narrow, with small epimera. 

 The epipleurae are narrow, and variable in form ; they are sud- 

 denly lobed in front, and extend to the apex in Lutrochus ; they 

 are not suddenly lobed, but extend to the apex, in Pelonomus ; 

 while in Helichus they are not lobed, and extend much less dis- 

 tinctly to the apex. 



