312 COLEOPTERA OF NORTH AMERICA. 



by the acutely triangular scutellum, and finely granulated eyes. 

 The last joint of the palpi never has the triangular form which it 

 afl*ects in most Ceraiubycini, but is usually oval, squarely truncate 

 at tip, with a deep elliptical impression on the side.* The tibiae 

 are not carinate, and the tibial spurs are rather long. 



The following groups may be recognized in our fauna: — 



Mandibles acute, or simple at tip; 



Prouotum broadly lobed at base ; poriferous system of antennae very 



distinct ; 



Metasternal pores absent, side pieces very wide. Megadeei 



Metasternal pores distinct. Trachydekes. 



Prouotum not lobed, sometimes subsinuate at base, poriferous system 



often obsolete, and palpi in some genera scaroely impressed. 



Stenaspes. 

 Mandibles emarginate at tip. Tyloses. 



Group I. — Megaderl. 



This group contains but one genus Megaderus, of which one 

 species, 31. bifasciatus Dupont (corallifer Newm.), extends from 

 Mexico into Texas. It is a broad, flat insect, with roughly 

 punctured prothorax, angulated on the sides behind the middle; 

 elytra finely punctured, with a basal and medial transverse band, 

 which are more or less confluent, separate, or even obliterated. 



The antennae are shorter than the body, with the 1st joint as 

 long as the 3d, and a little thicker; 3d and following with pori- 

 ferous spaces; outer joints velvety, 11th appendiculate, acute at 

 tip ; front rather flat, oblique ; gense long; mandibles stout, acute, 

 palpi short, last joint not elongated, oval truncate, deeply im- 

 pressed. Prothorax broad, strongly and broadly lobed at the 

 base, deeply excavated behind the middle, especially at the sides, 

 which are angulated ; scutellum very large, acutely triangular, 

 mesonotum sparsely punctured, with narrow medial stridulating 

 surface ; elytra finely densely punctured, rounded behind, sutural 

 angle not rounded, nor prominent. Pro- and mesosternnm very 

 broad, the former overlapping the latter, both broadly emarginate, 

 behind ; side pieces of metathorax very wide, epimera extending 



* Among tbe Cerambycini with coarsely granulated eyes I have observed 

 this form of palpi and the lateral fovea in Chion, which is an annectent form ; 

 and the same in a much less degree in some other genera. The maxillary 

 palpi are never short as in Callichromini, nor has the % an-additional 

 ventral segment. The front coxal cavities are open behind, and not 

 angulated externally. 



