Till': CKNTS DENDROCTONUS. 



59 



Whatever their origin may have been, the present function is to sup- 

 port the epipharynx and also serve as chitinous attachments for the 

 depressor muscles of the labrum. They are covered by the epipharynx 

 and extend down and back to the oesophagus and to a point beneath 

 the base of the clypeal area. 



Epimmial nturt' 



Occiput-' 



4Q.Dendroctonusvalens: Head of larva. A, Trans verse section; B, oral aspect; C, ventral aspect; D, \j 

 lotiKitu Jiiial section; E, dorsal aspect; a, muscles; b, submental lobe; c, maxilla; d, condyle of dorsal articu- 

 lation of mandible ; c, pleuix>stQma^Jiypopharvngeal bracon:g. fossa of ventral articulation of mandifcls^ i j 

 h, maxillary condyle; iJKular plate;77iaxillary foramen ; jj, oral foramen; k, attachment of epipharyngeal ^Tl/'t 

 bracons(labralhooks)f^pregenalarea; m, g**ie*area; ra/,g**toapodeme; n, attachment of labial muscle; 



0, frontal apodeme; p, integumental attachmeirfcsjj' occipital ipodeme; r, frontal apex; *, frontal suture; 



1, j)rcscutal lol>e of mesothoracic segment; u, scutelhH^pbe ofprothoracic segment: v, prescutal lobe; w, 

 hypopharyngeal bracon; x, sternal section of prothorachss^gm^nt; y, sternellar section of mesothoracic 

 segment, both distorted; z, apical papilli. (Original.) 



Clypeus. The so-called clypeus evidently does not represent an 

 entirely distinct element, but a produced dilated preepistomal area 

 or extension of the epistoma proper. In Dendroctonus larvae it is 

 twice as broad as long and narrowed toward the apical margin, 

 which is usually slightly emarginate. The basal connection with the 

 epistoma is continuous and rigid, and bears two widely separated 

 bristles near the base. The sides are rounded to a rather acute im- 

 pressed basal angle at the mandibular condyle. 



