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THE SCOLYTID BEETLES. 



Epistoma. The epistoma is quite clearly defined as a thickened 

 transverse area between the clypeus and the frontal area. It does 

 not extend laterally to the frontal sutures, but the ends, where they 

 join the pleural ridge or pleurostorna, bear the condyles for the dorsal 

 articulation of the mandibles. As in the adults, this area is quite vari- 



able within the genus. It is elevated to flat, with the anterior margin 

 ranging from curved to nearly straight and the lateral angles elevated 

 or slightly produced so as to form the rigid support for the dorsal 

 condyles. 



Hypostoma. The hypostoma is not represented by an exposed 

 piece, but by the apodeme which forms the thickened lateral and sub- 



