THE TRACHEATION OF WINGS 



37 



toward the reduction of the cubito-anal tracheae which are ver>' small and 

 are followed with difficulty in dissection. The tracheae to the legs are 

 unmodified except for the shortening of the anterior stem {as) to the hind 

 leg. 



EXAMPLES OF SPECIALIZATION BY REDUCTION 



The basal connections of the wing trachecB of Ryacophila, Order Trichop- 

 tera. — The wing trachea) of Ryacophila are greatly reduced and the basal 

 connections are correspondingly specialized. The thorax is specialized in 

 that there are marked intersegmental depressions on the sides, within which 

 the rudimentary spiracles are found. However, the connections to the legs 

 have retained their primitive condition. 



Fig. 26. — The basal connections of the trachea; of the 

 wings of Bittacomorpha. Side view. 



The wing tracheae of each wing appear to arise as two trunks which 

 connect indirectly with the mesothoracic spiracular trunk (Fig. 27, s/?i) 

 in the case of the front wing, and the metathoracic spiracular trunk {sp2) 

 in the case of the hind wing. The anterior trunk to each wing arises in 

 common with the anterior stem of the leg trachea and is undoubtedly the 

 costo-radial trachea (c-r). 



The cubito-anal trachea of each wing {cu-a) arises in its t\T)ical position 

 near the spiracle which nonnally supplies it with air. But owing to a 

 cephalization of its air supply which results in this trachea receiving the 

 greater part of its air by the way of the transverse basal trachea {tb) its 

 course becomes greatly modified and the proximal portion of it greatly 

 reduced. This results in that part of it beyond the point of union with the 

 transverse basal trachea appearing to be a continuation of that trachea. 



There has been developed a small accessory longitudinal trachea {a-dt) 

 which arises with the transverse basal trachea near the spiracular trunk 



