652 THE PANORPOID COMPLEX, ii., 



After the elimination of tlie arcliedictyon, the hases of inser- 

 tion of the macrotrichia left upon the membrane of tlie wing still 

 show, fairly plainly, the original pattern of the lost meshwork. 

 A study of the meshwork in the figures of Prototheora ali-eady 

 referred to will soon convince us that it is possible to reconstruct 

 the course of the meshwork with fair accuracy, by joining up 

 the bases of the macrotrichia along the lines which they still 

 indicate. The resulting figure will not be correct in all parti- 

 culars, since some of the cross- venules of the mesh do not carry 

 any macrotrichia at all, and would therefore be onntted in the 

 reconstruction; while, in a few cases, the positions of the macro- 

 trichia are more or less misleading. 



In specialised cases where the macrotrichia proliferate freely 

 on the veins and membrane, as in the case of the higher Hetero- 

 neurous Lepidoptera, there are always more than sufficient macro- 

 trichia to ensure an accurate tracing of the original pattern of 

 the archedictyon. This is well shown in the figures of the Hawk- 

 Moth Cmqiiosa triangularis Don., (Text- fig. 21). Here it will be 

 seen that the meshwork, probably while it was still aphantoneuric, 

 tended to become arranged into almost parallel lines connected 

 by irregular cross-pieces. It is this tendency, carried to its 

 highest development, that gives the very regular arrangement of 

 the scales seen in the Butterflies. But in all cases, by careful 

 study, it can be seen that the arrangement is a modification of 

 an original meshwork, and not a series of unconnected straight 

 lines. 



The evidence afforded by the archaic Bhi/phas in the Diptera, 

 and by both the Homoneura and the older types of the Hetero- 

 neura in the Lepidoptera, points definitely to the conclusion that 

 these two Orders, like the less highly specialised Orders of the 

 Panorpoid Complex, had their macrotrichia arranged upon the 

 membrane in the original positions which they occupied upon 

 the aphantoneuric archedictyon. 



The M i c r o t r i c h i a : — Though absent in the higher types 

 of some Orders, ^.y., Megaloptera, Planipennia, Diptera (a few), 

 and Lepidoptera (the great majority), yet they are found to be 



