26 clai'dh: fullek. 



which precede the forming veins," and accorded well with the 

 venation of the most generalised wings the}' presented. All 

 the principal veins are traced to two tracheae which enter the 

 wing-sac^ one on its anterior and one on its posterior border. 

 The anterior is described as " a branch of the dorsal longi- 

 tudinal trachea," the posterior, "of the ventral longitudinal 

 trachea." Unfortunately, these two tracheae are not further 

 defined. Such trachea? are present in our more generalised 

 termites (H o d o t e r m e s , C a 1 o t e r m e s , C r y p t o t e r m e s , and 

 Rhinotermes), but the basal connections of the wing 

 trachese are far removed fi'om them. According to the type, 

 each of the two wing tracheie, on entering the wing-sac, sub- 

 divided into four principal stems so as to form an anterior 

 and a posterior group. The anterior shows the costal, the 

 sub-costal, and the radial as outer branches of the medial 

 trachea ; the posterior shows three anals as inner branches of 

 the cubital trachea. To each principal trachea was given a 

 typical development, some being simple and others variously 

 branched (fig. 1, PI. III). 



As reflected in the figure, the type was enlarged as follows : 

 "' In most insects there has been developed a transverse 

 trachea connecting these two groups of tracheas. 

 Frequently the transverse basal trachea is indistinguishable 

 from the two main trunks which it connects, the three forming 

 a single, continuous transverse trachea from which arise all 

 the wing trachea?. . . . When a basal trachea is formed 

 the medial trachea tends to mio'rate alonu' it towards the 

 cubito-auftl group and often becomes united with that group. 

 In some cases the base of the radial trachea tends to follow 

 the base of the medial in its migration along the basal trachea 

 towards the cubito-anal group." This linking up of the two 

 groups of tracheie (as shown Ijy the dotted lines in the figure) 

 is regarded by the authors as a more s])ecialised condition. 

 Inasmuch as the i)rincipiil tracheal stems within the wing-sacs 

 oi' all the termites I have examined arc post-(!ml)ryonic 

 developments from the spiracular trunks' ;iiid not from the 

 ' See Section V for definition of " spiracular trunk," etc. 



