THE GENUS DENDROCTONUS. 



33 



riorly by the oblique sinuated line of the median suture and the 

 ■lateral section of the posterior ridge. 



Scutellum.— The scutellum is represented externally by the area 

 posterior to the oblique line of the median suture and by the sublat- 

 eral and lateral ridge which terminates in the scutellar process, as is 

 indicated by the character of the entotergum and by comparison 

 with the less modified scutellar division in other insects. The 

 median longitudinal groove appears to represent the median produced 

 section of the scutellum rather than a part of the scutum or prescu- 

 tum, as indicated by the character of the entotergum and the widely- 

 separated apodemes of the median suture which extend to and join 



Anterior apodeme 



/ V 

 / \ 5 Prcphragma. 



Membranous area 

 a / ^Anterior lohej 



Presculvm- 



i Proscutal diac 



. Vrrscuial lobe 



~)..Prcscutal process 



alcral emargmation 

 'y'iculi'.Uar process 



•Sciifal lobe 



Median apodeme 



'tistsculellar process 



'iQiclapleural hook 



Sculcll 



Piislplirogma 



Fig. 21. — Dendroctonus valens: Metatergum, inner aspect, a, Lateral arm of prephragma; 6, dorsal 

 band; c, scapular articulation; d, posterior angle of prescutum; e, posterior arm of postphragma; /, pos- 

 terior apodeme; g, anterior disk; li, posterior margin of scutellum; x, ventral wall of postscutellum. 

 (Original.) 



with the anterior apodeme (fig. 21), thus defining a large median 

 triangular area which is evidently scutellar. 



Postscutellum. — The postscutellum is the exposed dorsal and lateral 

 area between the clearly defined posterior suture and the line of 

 attachment of the first abdominal tergite. It is firmly connected 

 with the scutellum toward each side at a point near the base of the 

 oblique apodeme of the middle suture, otherwise the connection is 

 membranous. The anterior angles support the metapleural hooks 

 (fig. 20, £',u), which fit into a fold in the dorsal margin of the postepi- 

 merum (fig. 20, p). 



Postphragma. — The postphragma is an invagination of the pos- 

 terior section of the postscutellum and, with the produced posterior 

 disks and arms, serves as important posterior attachments for the 

 longitudinal, tergal, and oblique scutal muscles. 



