CHAPTER XIII 

 THE WINGS OF THE CORRODENTIA 



The winged members of this order have four membranous wings; the 

 fore wings are larger than the hind wings ; and both pairs when not in use 

 are placed rooflike over the body, being almost vertical, and not folded in 

 plaits. The wing-veins are prominent, but the venation of the wings is 

 reduced. 



The determination of the homologies of the wing- veins in this order was 

 a problem that sorely puzzled all who worked upon it until it was approached 

 by the ontogenetic method by Comstock and Needham. As soon as we 



4+5 



Fig. 255. — The wings of Psocus (After C. & N.). 



Studied the tracheation of the wings of nymphs the difficulties vanished. 

 These difficulties are due to the fact that what appear to be cross-veins are 

 sections of longitudinal veins. 



The type of venation of the wings characteristic of the Corrodentia is 

 well-illustrated by the wings of Psocus (Fig. 255). In the fore wings the 

 branching of the longitudinal veins corresponds quite closely with the 

 hypothetical type except that there is a reduction in the number of the 

 branches, subcosta being unbranched, and radius and media being each 

 only three-branched. In the hind wings, the venation is much more 

 reduced. 



A study of Figures 256 and 257, which represent two stages in the 

 development of the fore wing of Psocus will convince one of the correctness 

 of the homologies of the veins indicated in Figure 255. These figures were 



(258) 



