THE WINGS OF HYMENOPTERA 



369 



Again, in the Hymcnoptera, we found that the courses of the tracheae 

 cannot be depended upon for determining the homologies of the wing-veins, 

 notwithstanding the fact that in the more generahzed members of the order 

 a very complete system of wing-tracheae exist. The wings of a pupa of 



Fig. 389. — Wings of a pupa of Tremex (From C. & X.). 



Tremex (Fig. 389) illustrate the extent to which the tracheae are retained in 

 the more generalized members of the order; and the wings of Apis (Fig. 

 390) illustrate the tracheation of the wings in a more specialized form. • 



The most striking feature of the courses of the main tracheae in the wings 

 of Tremex is that each extends in a nearly direct line from the base of the 

 wing to near its outer margin ; and that while in most cases the basal part 

 of each lies in the cavity of the vein with which it corresponds, this corres- 

 pondence does not extend to the branches of the principal veins. 



Fig. 390. — Wings of a young pupa of Apis (From C. & N.). 



Even in the case of the principal veins, this correspondence is not com- 

 plete; for the basal part of the radial trachea of the fore wing lies in what is 

 without doubt the cavity of subcosta; and in both wings the medial 

 trachea does not extend into the branches of the media. 



In the course of a study of the development of the wings of the honey- 

 bee, Dr. Needham and I discovered the cause of the lack of con-espondence 



