THE GENUS DENDKOCTOISrUS. 



41 



Primary elements of the Dendroctonus wing. — The primary wing 

 elements and their relations to each other as represented in Den- 

 droctonus may be summarized as follows: The structure consists of a 

 dorsal and ventral membrane or chitinous integument. The primary 

 trachese are costal, subcostal, radial, cubital, and anal. The primary 

 veins are costa, subcosta, radius, media, cubitus, and anal. The 

 wing plates are scapular, subscapular, flexor, subflexor, radial, and 

 medial. The wings are attached by membrane to the tergum and 



VENTRAL 

 Fig. 27. — Dendroctonus: Left tibiae, dorsal and ventral aspects. 1 , brevicomis; 2, barberi; 3, convexifrons, 

 i, frontalis; 5, arizonicus; 6, mexicanus; 7, paraUclocolUs; 8, approximatus; 9, monticolse; 10, ponderosse. 

 (Original.) 



pleurum, and by Kgaments and tendons to tergal and pleural proc- 

 esses and muscle disks. The pleural processes are the clavicle and 

 coracoid processes, which together form the pleural clavicula. The 

 tergal processes are the prescutal, scutellar, and postscutellar. 



Elements of wing motion. — The elements of wing motion are the 

 clavicular disk and clavicular muscle, pleural disk and pleural muscle, 

 flexor and flexor muscles, prescutal disk and muscles, anterior pres- 

 cutal lobe and anterior sternotergal muscles, posterior prescutal lobe 

 and posterior sternotergal muscles, scutal lobe and scutal muscles, 



