38 



THE SCOLYTID BEETLES. 



ABDOMINAL PLEURITES. 



At the lateral ends of the abdominal tergites and sternites there 

 are well-defined areas (figs. 3, 22, 25), which may be designated as 

 pleurites. Those situated immediately above the pleural suture and 

 bearing the spiracles may be referred to as epipleurites, while those 

 of the sternites which are immediately below the pleural suture may 

 be designated as hypopleurites; both series are well defined in 

 Dendroctonus. 



In a lateral view (fig. 3) seven epipleurites and five hypopleurites 

 are clearly defined, with the eighth epipleurite and the second hypo- 

 pleurite indicated, and when the abdomen is removed both the first 

 and second of the latter series are quite distinct. 



Ilypopleurites . ^ 



Coxal cavitu 



Inlercoxal process 



FIG. 25. Dendroctonus valens: Abdominal sternites, ventral and lateral aspects. A , Lateral; B, ventral; 

 a, sternite 1 , faintly indicated; 6, sternite g, faintly indicated. (Original.) 



ABDOMINAL STERNITES. 



The characters of the abdominal sternites are shown in figures 2, 

 3, and 25. There are eight, corresponding to the eight tergites, but 

 only five are exposed, viz, 3 to 7, which are densely chitinized and 

 clearly defined by four sutures. 



Sternites 1 and 2 and the anterior portion of 3 are covered and 

 obscured by the large metacoxa and form the posterior wall of the 

 coxal cavity. They are fused, but the sutures are indicated by faint 

 lines. Sternite 3 (first ventral segment of some writers) has the 

 median area produced anteriorly, and with faintly indicated median 

 portions of sternites 2 and 1 it forms the intercoxal process, the apex 

 of which forms a junction with the metasternellar piece. The 

 anterior exposed margin forms the posterior margin of the coxal 

 cavity, but the junction with the preceding segment is but faintly 



