42 



THE TRACHEATION OF WINGS 



EXAMPLES OF SPECIALIZATION BY ADDITION 



The basal connections of the wing trachece of a nymph of Melanoplns sp., 

 Order Orthoptera. — The dissection of an acridid nymph is rather difficult 

 because of the many tracheal branches and air sacs in the thoracic region. 

 The minor branches and the air sacs were removed in the course of the 

 dissection and the figure is a camera-lucida drawing of the tracheas with 

 which this paper is concerned together with the more important minor 

 branches. 



The tracheal connections are modified to a certain extent but the condi- 

 tions are easily explained (Fig. 33). The point of union of the costo-radial 



Fig- 33- — The basal connections of the trachefe of the wings 

 of Melanoplus. Side view. 



trachea (c-r) and the anterior stem of the leg trachea (as) has moved dorsad 

 in both cases. In the mesothorax the anterior stem to the leg arises from 

 the spiracular tnuik (5^1) and goes dorsad to the point where the costo- 

 radial trunk (c-r) is given off and then it passes ventrad to meet the posterior 

 stem (^.s-) thus forming the usual Y-shaped trachea to the leg. It will be 

 noticed that the posterior stem is the larger of the two. 



From the costo-radial trachea (c-r) of the front wing there is an acces- 

 sory trachea (a. c-r) which connects with the saclike dilated dorsal longitu- 

 dinal trachea ((i./O- The base of the cubito-anal trachea (cu-a) has fused 

 with the anterior stem (as) to the metathoracic leg to fonn a common 

 trunk extending dorsad for a short distance from the metathoracic spiracle. 

 The cubito-anal trunk {cti-a) to the front wing has an accessory tracheal 



