THE TRA CREATION OF WINGS 



39 



absent. However the reduced cubito-anal trachea (cu-a) is present in the 

 thorax with its typical connections except that it fails to reach the wing. 

 The leg tracheae have the typical connections. 



The basal connections of the wing trachece of Stenophylax, Order Trichop- 

 iera.— The cubito-anal tracheae (Fig. 29) do not reach the wing in either 

 case in this form altho their vestiges are present in the thorax (cu-a) and 

 both have their typical connections with the posterior stems of the leg 

 tracheae (ps) . In both cases the costo-radial tracheae {c-r) have their typical 

 connections except that the transverse basal tracheae are entirely absent. 



The basal connections of the wing trachece of a nymph of Epeorus. Order 

 Ephemerida. — The wing tracheas of Ma\^ies are highly specialized and 



Fig. 29. — Tlie basal connections of the trachcse of the wings of 

 Stenophylax. Side view. 



there is a marked cephalization of the flight function in this order. Morgan 

 in a paper on the wings of May-flies (Morgan, Anna H. Homologies of the 

 wing veins of the May-flies, Annals, Ent. Soc. Amer. 191 2, v. 5, p. 89-105), 

 concluded that the wing tracheae of Epeorus represented one of the more 

 generalized conditions. For this reason Epeorus has been used for the 

 study of the basal connections of these tracheae. 



The anterior tracheae to each leg and wing have retained their primitive 

 conditions (Fig. 30); the anterior stem of the leg tracheae {as) and the 

 costo-radial trachea (c-r) to the wing have a common origin in each case. 

 However the posterior connections to the wings and legs have been greatly 

 reduced. The portion of the cubito-anal trachea (cu-a) proximal to its 

 union with the transverse basal trachea (tb) is absent except for a short 

 vestige in the front wing. This short vestige extends proximally from the 



