THE WINGS OF INSECTS. 
J. H. COMSTOCK anD J. G. NEEDHAM. 
CHAPTER ‘III (continued). 
VIII. THE VENATION OF THE WINGS OF DIPTERA. 
In the order Diptera, as in the Trichoptera, a great reduc- 
tion of wing trachez has taken place. Owing to this fact we 
have not found that any light is thrown on the question of the 
homology of the wing-veins by a study of the tracheation of 
the wings of dipterous pupz. We will, therefore, confine our 
attention in this place to a study of the wings of the adult. 
In this order the tendency towards a cephalization of the 
flight function, which occurs in nearly all of the orders of 
Fic. 29. — Wing of Rhyphus. 
winged insects, reaches its maximum development, and has re- 
sulted in the complete suppression of the hind wings as organs 
of flight. 
Notwithstanding this great modification of the organs of 
flight, the remaining pair of wings retain, in the more general- 
ized members of the order, the primitive type of wing vena- 
tion but slightly modified. So unimportant are the changes 
that the determination of the homologies of the wing-veins in 
these forms presents no difficulties. 
If a wing of Rhyphus (Fig. 29) be compared with our 
hypothetical type (Fig. 5)!, it will be found to correspond very 
1 American Naturalist, April, 1898, No. 376, p. 251. 
