THE GENUS DENDROCTONUS. 



13 



Epistomal process. In Dendroctonus the epistomal process serves 

 to clearly distinguish the genus from other genera of the suborder to 

 which it belongs. This process is usually composed of a median and 



FIG. 5. Dendroctonus valens: Head, ventral aspect, and mouthparts. A, Labimn; B, maxilla, interno- 

 lateral aspect; C, same, externo-lateral aspect; D, hypostomal region, dorsal aspect; E, head, ventral 

 aspect; a, basal fossa of mentum; 6, joints; c, basal membrane; d, palpiferal area; e.stipal area;/,sub- 

 galeal area; g, fossa; h, muscle processes; k, median condyle; I, lateral fossa; TO, anterior condyle; n, 

 median fossa; o, posterior condyle; p, hypopharyngeal bracon; q, submental process; r, maxillary con- 

 dyle; s, gular apodeme; u, oral foramen; v. occipital apodeme; w, postgular piece. (Original.) 



two lateral sections and is fringed anteriorly with thickly set, long 

 bristles which completely cover the anterior median epistomal area. 

 Hypostoma (fig. 5). This, as here interpreted, is a ventral piece 

 or area which corresponds in general function to the epistoma in 

 forming a rigid ventral rim of the oral foramen for the support of the 



