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. a.— Dendroctonus valens: Head, ventral aspect, and mouthparts. A, Labium; B, maxilla, intemo- 

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

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

 galeal area; g, fossa; h, muscle processes; fc, median condyle; I, lateral fossa; m, anterior condyle; n, 

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

 dyle; s, gular apodeme; m, oral foramen; z;. occipital apodeme; ?«, 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 



