THE WINGS OF ODONATA 



227 



The degree of perfection of the alternation of convex and concave veins 

 that has been evolved in the wings of these insects is shown in the following 

 table by the use of two kinds of type, one indicating convex veins and the 

 other concave veins. 



As a branch of a convex vein may be concave, or a branch of a concave 

 vein be convex, it is necessary, in order to indicate the relation of the corru- 



C/ii Ciii 



Fig. 229. — Wings of Gomphus descriptus. In the front wing cells or areas 

 are labeled; in the hind wing, veins. 



gations to the venation, to indicate the nature of each vein in different parts 

 of the wing. For this purpose four transverse lines have been selected and 

 the nature of the veins crossed by each is indicated in a separate column. 



'2 "I Cur ^"^ 



Fig. 230. — Base of wing of Cordulegasler sayi. 



