70 



AN INTRODUCTION TO ENTOMOLOGY 



Fig. 83. — Wing 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 

 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 /, 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 is desig- 

 nated as ICui. 

 The adven- 

 titious veins. — 

 In certain in- 

 sects there are 

 secon d ary 

 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 



St A 



3dA 2d A '^ 



Fig. 84. — Wings of Prionoxystus. 



certain Odonata and the spurious vein of the Syrphidae. 



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

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



