14 



THE SCOLYTID BEETLES. 



articulatoiy accessories of the labium and niaxillse, and at the lateral 

 angles supports the ventral articulations for the mandibles. It 

 seems to the writer that this part or area, whenever sufFicientl}^ dis- 

 tinct to be recognized, should be designated as the hypostoma, not 



^ Epistoma ^^ 



Dorsal ftrticiiJollon 



A " 



Epi.sloinal process 



-■ Lateral section 



Gutar suture 



Fig. 6. — Dendroctonus valens: Head, oral aspect, epistoma, etc. A, Ventral aspect of epistomal region; 

 -B, dorsal aspect of epistomal region; C, oral aspect of head; a, median impression and longitudinal ele- 

 vations; 6, median condyle; c, lateral fossa; d, posterior fossa; dd, projection over median condyle; e, 

 base of epistomal bristles;/, median section of epistomal process; ff, lateral angles of epistoma; g, ante- 

 rior fossa; A, anterior condyle of ventral articulation; «', posterior condyle of ventral articulation ;j, median 

 fossa of ventral articulation; k, hypopharyngeal bracon; I, maxillary condyle; m, submental processes; 

 m, ventral view of hypopharynx; o, oral foramen; p, dorsal articulation of mandible; q, ventral articu- 

 lation of mandible; r, apex of hypopharynx. (Original.) 



on account of any theory of origin from a primitive segment, but 



because its location and function are similar to those of the epistoma. 



Front (figs. 3, 4). — The front is not defined by sutures or lines, but 



is fused anteriorly with the epistoma and laterally and posteriorly with 



