THE GENUS DENDROCTONUS. 



35 



ventral angle or ventral section of the postepimerum, which might 

 be mistaken for a postepisternum, is indicated by the pleural apodeme 

 and pleural suture w r hich here join the dorsal angle of the coxa. It 

 is not impossible, however, that this plate may represent a combined 

 postepisternum and postepimerum. 



METASTERNA. 



.e metasterna (figs. 2, 3) form a broad rectangular plate separated 

 to two lateral sections by a median longitudinal line. The pre- 

 sternum and poststernellum are not represented by external parts. 



,-Spiracle I 

 -Epipleuritel 



~ Epipleurite 2 

 - -SpiracleS 

 - Epipleurite 3 



-Epipleurite 4 



-J~*Spirack 5 

 Epipleurite 5 



-/-- Spiracle Q 

 ~ 'Epipleurite 6 



''^Spiracle 7 

 ^Epipleurite 7 



Pygidium 



'Stridulating scraper 



FIG. 22.Dendroctonus valens: Abdominal tergites. a, Anterior arm of epipleurite 7; 6, posterior arm of 

 epipleurite 7; c, membranous lobes. (Original.) 



Sternum. The sternum is evidently represented by the large con- 

 tinuous area between the mesocoxse and the small median plate and 

 the slightly acclivous area anterior to the metacoxa. 



Sternellum. The sternellum is evidently represented by the pos- 

 terior median plate and the posterior acclivous areas (fig. 2, a). The 

 relation of the latter to the sterneilar area is indicated by the attach- 

 ment of the posterior pair of clavicular muscles. 



THE ABDOMEN. 



The abdominal terga, pleura, and sterna, and their relative pro- 

 portions, are shown in figures 1-3 and 22-25. 



7998009 4 



