THE GENUS DENDEOCTONUS. 



43 



general position to that of the primary veins in the latter, thus con- 

 forming to the prevailing system in fully developed wings of all 

 msects. The primary tracheae are costal, subcostal, radial, medial, 

 cubital, and anal. In the elytron these occupy the marginal and 

 alternating interspaces between the longitudinal striae or rows of 



VENTRAL 



Fig. 29. — Dendroctonus: Left tibiae, dorsal and ventral aspects. ^0, punctatus; 21, micans; 22a, 22b, 



terebrans; 23, valens. (Original.) 



punctures, while in the hind wing they follow approximately the 

 primary veins. 



Metathoracic or Hind Wings. 



The hind or metathoracic wings (figs. 1, 20, and 30) are a third 

 longer than the elytra or mesothoracic wings, under which they are 

 folded when at rest. Li consequence the veins toward the middle 

 of the wings are flexible and adapted to the requirements of foldmg 

 and unfolding. 



