36 



THE TRACHEATION OF WINGS 



condition of the tracheas of the metathorax is similar to that of the meso- 

 thorax except that the costal trachea (c) has retained its typical position 

 and the cvibito-anal trachea {cu-a) has moved slightly forward and might 

 almost be said to arise from the anterior stem of the leg trachea {as) in the 

 absence of the posterior stem from which it typically arises. 



The basal connections of the wing trachea of Monohanimus, Order Coleop- 

 tera. — The wing tracheae of the Coleoptera have retained their original 

 relationships to the spiracular trunks but there is a modification of the leg 

 trachccc. Both of the posterior stems of the leg tracheag (Fig. 25, ps.) are 

 split nearly to their basal connections and they are entirely independent of 



Fig. 25. — The basal connections of the tracheae of the wings 

 of Monohamus. Side view. 



the cubito-anal tracheae {cu-a). The anterior stem of the leg tracheae {as.) 

 of the metathorax is very slender but it has retained its original connection 

 with the costo-radial trachea {c-r). In the mesothorax the anterior stem 

 of the leg trachea is entirely absent. 



The longitudinal trachea is well developed and the position of the meta- 

 thoracic spiracle, which is absent, is indicated by the spiracular trunk 

 {v. sp2). None of these conditions seem to have modified the original 

 relationship of the wing tracheae to the spiracular tnmks. 



The basal connections of the wing trachece of Bittaconiorpha, Order Diptera. 

 — The connections in this form are rather generalized and even tho the hind 

 wing is absent the halter receives tracheae which have all the relationships 

 that the tracheae to the wing would have (Fig. 26). There is a tendency 



