SOUTH AFRICAN TERMITES. 59 



The unfolding and spreading of the wing takes place ironi 

 'the stump outwards, as seen in the nine diagrams, figs. 65a 

 to K, prepared from wings of T. iiatalensis. During this 

 period the insect walks about holding out its wings in the 

 attitude depicted by fig. ()G. The process may well be 

 likened to the billowing out of a crumpled and wet cloth by 

 di'iving a blast of air below it, compare figs. 67a, b, c, d, 

 which represent wings of T. natal en sis in four degrees of 

 unfolding. In this insect the tracheas maybe found, practically 

 intact, in the wing stumps ; but there are no air-passages 

 through the ribs, fig. 67d. The radius, pseudo-media, and 

 cubitus appear, however, perforated by a minute capillary, 

 which is probably ill -defined because filled with a fluid. 

 What seems to happen to the trachege is that they are 

 stretched until the spiral is unwound, and are then 

 absorbed ; this conclusion is based upon the occasional 

 presence of frayed-out tracheae in the more apical part that 

 has just unfolded ; such were present in the wing shown as 

 fig. 67d. It is very obvious that the minor trachea) are 

 absorbed, and there is some reason to believe that this takes 

 place before the final ecdysis. 



VIII. THE VAEIATION IN THE VENATION. 



Some reasons have already been stated which will account 

 in part for the variation in the venation and for the extreme 

 variableness of the reticulation. 



Final wings differ so much in detail that it is impossible to 

 put aside as quite alike any two, even of one insect. It may, 

 however, be said that the more specialised the species, the 

 more is the venation of one wing agreeable to that of its 

 companioai, and, the more generalised, the greater the irregu- 

 larities. This is largely because the more generalised species 

 have more reticulate wings. 



In the preceding section the statement is made that 

 thickenings form about the tracheae. To this it may be 

 added that the ribs of the final wing are transformed thicken- 



