634 THE PAKORPOID COMPLEX, ii,, 



these veinlets cany loacrotricliia, it will be obvious that, as they 

 disappear, the iiiacrotrichia will become seated upon the mem- 

 brane. 





Text-tig. 20. 

 Pteiostigmatic area of forewing of Micromua tasiiuini(x Walk,, showing 

 aphantoneuric condition of the veinlets; { x 15). C, costa; R, radius; 

 Sc, subcosta. 



Thus we see that the evidence both of the fossil Order Proto- 

 mecoptera and of the recent Planipennia agrees in pointing to 

 the same conclusion: — Macrotrichia icere oriyinaUy carried only 

 upon the main veins and their branches^ and upon the archedictyon; 

 they ajypear upon the membrane by absorption of the veinlets or 

 venules^ carrying thein^ into the membrane of the iviny. 



From this we come to the further conclusion that: — The 

 2)resence of macrotrichia upon the inembrane of ivings of oai open- 

 veined type (i.e., one ichich has no close meshivork of numerous 

 veins) is to be regarded as evidence of the descent of sack forms 

 from more deitsely veined forms. 



The process by which the archedictyon, or any series of vein- 

 lets, becomes merged into the membrane, may be termed aphan- 

 toneurisnt, and veins which are in process of disappearing in 

 this manner may be called aphantoneuric. It is often possible 

 to reconstruct the aphantoneuric meshwork, merely by plotting 

 the positions of the macrotrichia upon the membrane, and join- 

 ing them up into a polygonal meshwork. Text-fig. 21 shows a 

 reconstruction of a small portion of the aphantoneuric meshwork 

 of the Hawk-moth Cceqnosa triangularis Don. 



Having now explained how the Wing-trichiation is connected 

 with the venation in general, we may proceed to trace out the 

 various lines of evolution within the Orders of the Panorpoid 

 Complex. 



