70 



AN INTRODUCTION TO ENTOMOLOGY 



Fig. 83. Wings of a May-fly (After Morgan). 



mon in the Ephemerida, where most of the intercalary veins remain 

 distinct from the veins between which they were developed, being 



connected with 

 -C- 



them only by 

 cross-veins, the 

 proximal end of 

 the intercalary 

 vein being free 

 (Fig. 83). 



When it is 

 desirable to re- 

 fer to a parti- 

 cular interca- 

 lary vein it can 



be done by combining the initial 7, indicating intercalary, with the 

 designation of the area of the wing in which the intercalary vein occurs. 

 For example, in the wings of most May-flies there is an intercalary 

 vein between veins Cui and Cu2, i e. in the area Cui; this intercalary 

 vein iis desig- 

 nated as ICui. 

 The adven- 

 titious veins 

 In certain in- 

 sects there are 

 secondary 

 veins that are 

 neither acces- 

 sory veins nor 

 intercalary 

 veins as de- 

 fined above ; 

 these are 

 termed adven- 

 titious veins. 

 Examples of 

 these are the 

 supplements of. 

 the wings of 



Fig. 84. Wings of Prionoxystus. 



certain Odonata and the spurious vein of the Syrphidas. 



The anastomosis of veins. The typical arrangement of wing-veins 

 is often modified by an anastomosis of adjacent veins; that is, two 



