THROSCIDAE. 157 



hind coxte is but slightly concave, and the prolongation of the 

 abdomen extends a short distance along the side pieces of the me- 

 tathorax ; the sides of the prothorax beneath are deeply grooved 

 near the margin, for the reception of the antennae ; the legs are 

 very contractile, the tibiae usually sulcate for the reception of the 

 tarsi, which are very short; the scutellum is triangular. Three 

 of the four forms, which, following the example of Lacordaire, I 

 considered as groups of species, have been regarded by others as 

 genera, and may be distinguished as follows : — 



Body elongate ; scutellum small ; presternum pointed behind. 



Taphrocerps. 

 Body ovate ; scutellum small ; presternum obtuse behind ; tibise linear. 



Bkachys. 

 Body triangular ; scutellum large ; presternum very broad, almost truncate 

 behind ; tibia? dilated. Metomus. 



Fam. XXXIV.— THROSCIDAE. 



Mentum small, narrowed in front; ligula membranous, not 

 prominent; palpi short, 3 jointed. 



Maxillae exposed at the base, with two lobes, inner one 

 very small; palpi 4-jointed. 



Antennas inserted on the front, received in grooves extend- 

 ing along the inferior margin of the prothorax, 11-jointed; 

 sometimes serrate, sometimes with a loose serrate 3-jointed 

 club. 



Head immersed in the thorax to the eyes, which are ellip- 

 tical; mouth inferior, applied to the prosternum; mandibles 

 small; labrum prominent. 



Prothorax with the side pieces not separate, deeply sulcate 

 along the sternal suture, for the reception of the antennae ; 

 coxal cavities small, open behind, being completed by the 

 mesosternum; prosternum with an anterior rounded lobe 

 protecting the mouth, prolonged behind into a flat process 

 received in the mesosternum. 



Mesosternum short, excavated in the middle for the pro- 

 sternum, completing on each side the anterior coxal cavities; 

 side pieces very transverse, attaining the coxae. 



Metasternum with the side pieces very narrow. 



Elytra entirely covering the abdomen; epipleurse distinct. 



Abdomen with five ventral segments, not connate, though 

 closely connected. 



