THE TRACHEATION OF WINGS 51 



regard to the general subject of the basal connections of the wing tracheae 

 which are clearly brought out by the study of the material presented. 



It has been shown that the basal connections of the tracheas of the wings 

 of insects may be referred to a typical condition which is found in the more 

 generalized forms and which may be traced thru various modifications to 

 the more specialized groups. 



Very generalized conditions of the connections have been found in the 

 Blattidag, among the Orthoptera, the Plecoptera, Neuroptera, and the 

 Lepidoptera. The Hemiptera, Coleoptera, and Diptera show the begin- 

 nings of specialization but have been grouped with those having generalized 

 conditions. 



The typical conditions of the connections of the wing tracheae have been 

 specialized by reduction in the Trichoptera, Ephemerida, and the Hymen- 

 optera and this modification accompanies the specialized condition of the 

 thorax. 



In other groups, the jumping Orthoptera and the Odonata, the tracheal 

 connections of the wings have been modified by the addition of accessory 

 tracheas and this condition is correlated with the position of the wing pads 

 which are dorsally flexed in the nymphs of these two groups. 



Peculiarities of thoracic structure seem to be the most important factor 

 in governing the course and relationships of the tracheas. Processes and 

 apodomes have been found to lie in the typical paths of the tracheae so 

 obstructing them that the trachea could not do otherwise than go around 

 them even tho their course was lengthened by so doing. 



The directness of the air supply does not seem to be an important factor 

 in controlling the course and relationships of the tracheae. Both the 

 migration of the medial trachea toward the cubito-anal group, along the 

 transverse basal trachea, and the invasion of the area of the radial sector by 

 the medial trachea in the wing have been found to take place without regard 

 to the directness of the source of the air supply. 



