45 



fact mentioned earlier in this paper, that, like the other nervures, it 

 carries sensory hairs or bristles. 



Poulton's line is therefore the pupal indication of the marginal 

 nervure or trachea. The space between it and the pupal wing 

 margin represents the portion of wing outside this trachea, a normal 

 and constant portion of the wing, present in all cases, and therefore 

 always present in the pupa also. 



We may call this the ciliary margin, although the actual base or 

 origin of the cilia is not always accurately marked off by the marginal 

 trachea. 



