28 THE TRACHEATION OF WINGS 



the medial trachea when it is formed. Concerning this they made the 

 following statement: "It is probable that these changes have to do with 

 improving the air supply of the wing; but we have not sufficient data, as 

 yet, to warrant a definite statement on this point." 



A desire on the part of Professor Comstock to have ascertained the exact 

 nature of the basal connections of the trachea of the wings in different 

 orders of insects, in the hope that this knowledge would throw light on this 

 problem, led him to suggest the making of the investigation the results of 

 which are given here. 



Another condition that suggested the same question is the fact that in 

 the Odonata the branches of the medial trachea invade the region of the 

 tracheae of the radial sector, which becomes greatly reduced. If the medial 

 trachea has a better air supply than has the radial trachea, this invasion 

 can be understood. 



The references to the basal connections of the wing tracheae which have 

 been found in literature are few and fragmentary. So far as can be deter- 

 mined no general study of the subject has been made previously. How- 

 ever, various authors, while working on closely related subjects, have noted 

 and described the conditions in certain forms. These descriptions may 

 be best referred to in the parts of the paper relating to these various 

 forms. 



However the work of Karel Sulc [Uber Respiration, Tracheensystem 

 und Schaumproduction der Schaumcikadenlarven (Aphrophorinae- 

 Homoptera) Zeitschrift fiir wissenschafliche Zoologie. 1911:99, p. 147-188] 

 deserves special mention. This author described and figured the tracheal 

 system of Philaenns lineatus L. with detailed drawings of the leg and wing 

 tracheae in the various nymphal stages. The basal connections of the wing 

 trachete are more generalized than those of the Hemiptera described and 

 figured in this paper (Figs. 22, 23, and 24) and agree with the typical 

 condition of the wing tracheae (Figs. 1 7a and 1 7b) except that the transverse 

 basal trachea has been developed. The basal connections of the fore wing 

 pad of a first stage nymph of Aphrophora salicis are described and figured in 

 which the transverse basal trachea is not developed and the costo-radial 

 and cubito-anal groups of tracheae are shown arising respectively from the 

 anterior and posterior stems of the leg tracheae. 



Careful dissection was found to be the best means of studying the 

 tracheae. The use of transmitted light to distinguish the opaque tracheae 

 in the more or less transparent bodies, without dissection, was not satisfac- 

 tory because it was not possible, in this way, to accurately determine the 

 relationships of the tracheae which lie one above the other. Nymphs and 

 pupae were dissected under water and care was taken not to break large 

 trachejc and allow the air to escape. In this way the trachere were kept 

 filled with air and were easilv studied. Several dissections were made of 



