THE GENUS DENDEOCTONUS. 



31 



tellum. We also find that these transverse sutures are subject to 

 great variation in position, contour, character of surface, manifesta- 



FiG. 20.— Dendroctonus valens: Metatergum and metapleurum. B, Anterior aspect of prephragma and 

 prescutum; D, metatergum and metapleurum; E, posterior aspect of postpliragma and postscutel' 

 lum; a, lateral arm of prephragma; 6, dorsal band; c, scapular plate; d, subscapular plate; e, flexor 

 plate; /, radial plate; g, medial plate; /(, lateral arm of postphragma; i-i, metatergal costse; j, anterior 

 disk; fc, scutellar groove; I, posterior ridge; o, exposed triangular plate of postepimeron; p, pleural 

 hinge; pc, pleural clavicula; q, posterior ventral angle of episternum; r, anterior ventral angle of 

 epistemum; s, pleural suture; t, postscutellar process; u, clavicle condyle; v, coracoidal condyle; 

 w, attachment and articulation of scapular plate; x, dorsal area of postscutellum; y, pleural disk; 

 2, elevated acute margin; zl, membranous arsa; z2, villous area. Wing veins: C, costa; ^CjSub- 

 costa; R, radius; M, media; Cu 1, cubitus 1; Cu 2, cubitus 2; A, anal. (Original.) 



tions, etc., to correspond with the enormous range of modification to 

 which one or ah four of the transverse divisions are subject. Tliese 

 external evidences of separation of parts are here referred to as sutures, 



