THE TRACHEATION OF WINGS 



29 



each species and the results were carefully checked over to make sure that 

 no tracheae had been broken or overlooked. 



The dissections were drawn with a camera-lucida before the air had 

 escaped from the tracheae and while the trunks retained their normal size. 

 It is to be noted that no pretense has been made to include all of the muscle 

 tracheae; only the larger muscle tracheae connected with the wing or leg 

 tracheae have been shown. 



rt'.//-^ 



THE TYPICAL ARRANGEMENT OF THE BASAL CONNECTIONS OF THE 

 TRACHEA OF THE WINGS 



Two diagrams of what seems to be the typical condition of the basal 

 connections of the wing 

 tracheae have been con- 

 structed (Fig. 17). The 

 condition of the tracheal 

 branches to the wings and 

 legs, as figured in these 

 diagrams, does not differ 

 in any of its essentials from 

 the condition found in the 

 more generalized insects. 

 It will also be noticed that 

 none of the insects studied 

 present conditions which 

 cannot be looked upon as 

 modifications of this typi- 

 cal condition. The con- 

 struction of these diagrams 

 is, therefore, necessary only 

 to simplify the discussion 

 of the modifications of 

 the typical condition and 

 not to represent an imagin- 

 ary step in the develop- 

 ment of any of the condi- 

 tions found in any of the 

 more specialized insects 

 studied. 



One of the diagrams 

 (A) is a side view of the 

 thoracic tracheae in which 

 the wing tracheae are represented as extending vertically above the thorax 

 and those of the legs extending downward. The other diagram (B) is|a 



Fig. 17. — The typical condition of the basal con- 

 nections of the tracheae of the wings of insects. 

 A. Side view. B. Dorsal view. 



