20 



THE TRACHEATION OF WINGS 



metamorphosis the development of the tracheation of the wings presents 

 some of the more remarkable features of this highly specialized mode of 

 development. 



As an understanding of the more general features of the internal develop- 

 ment of wings is essential to an understanding of the development of the 



RJrM^ 



Fig. II. — Diagram of an arculus of a dragon-fly. 



tracheation of the wings of larvse and pupae a discussion of this subject is 

 omitted here, and will be taken up in Chapter V. 



Variations in the extent of the tracheation of the wings of nymphs and 

 of pupae. — While the study of the tracheation of the wings of njTiiphs and 

 of pupag has yielded most valuable data for determining the homologies of 

 the wing-veins of adult insects, an extended investigation in this field has 

 revealed remarkable differences in the extent of the tracheation of the 



Fig. 12. — The wings of a nymph of Nemonra (After C. & N.). 



wings of immature forms and in the degree of its correspondence with the 

 venation of the wings of adults. In some of the orders of insects, the 

 tracheation of the developing wings is of the greatest importance in deter- 



