228 



THE WINGS OF ODONATA 



TABLE OF THE WING-VEINS OF THE ODONATA 



The convex veins are indicated by boldface type 



BASE OF WING 



Costa 



Subcosta 



BEYOND ARCULUS 



Costa 



Subcosta 

 R 



BEFORE NODUS 



Costa 



Subcosta 

 R 



Mi+2 



BEYOND NODUS 



Costal margin 



R + M \ Mi+2+3 



Cu + A 

 A' 



M4 



Cu 



br 



M3 

 M4 



Cui 



CU2 



Beyond the nodus, there are present, in addition to the veins listed in 

 the last column, a variable niimber of intercalary veins. As a rule these are 

 alternately convex and concave where more than one are present between 

 two primary longitudinal veins. 



The alternation of convex and concave veins, as shown in the table, is 

 perfect in each of the four selected regions of the wing. In the attainment 



Cu+A 



Fig. 231. — Wing of Diastatomma Hasina. (Westwood's figure enlarged.) 



of this result some remarkable changes in the nature of veins have taken 

 place. When the convex vein M separates into two stems beyond the 

 arculus, vein Mi+2+3 becomes concave while vein M4 remains convex. 

 The concave vein Cu separates into the concave Cui and the convex Cu2. 

 It is impracticable to introduce the intercalary veins into this table on 

 account of their variability in nimiber and extent of development in differ- 

 ent members of the order. An exception has been made in the case of vein 

 IMi, in the last column. This has not been done merely to make perfect 

 the alternation of convex and concave veins listed in this column ; although 



