640 



THK PANORPOID COMPLEX, 11. 



l)e accoiiuiiodated in the somewhat narrow spaces between the 

 main veins, the original pattern of the archedictyon tends to 

 bc'cumc lost, and the maci'otriehia of the membrane tend to 

 become arranged in regular sets occupying the central part of 

 any closed area of the wing. 



The line of evolution in this Order is towards a gradual 

 elimination of the macrotrichia from the membrane of the wing, 

 and a reduction in their size elsewhere. In the most archaic 

 families, such as .Ueropidce (Text-fig. 25) and ChoristidfP. (Plate 

 Ixix., fig. 13), these hairs are still to be found upon the membrane, 

 in almost every part of the wing. In the Panorjndce, we may 

 see the stages of gradual elimination from the basal areas of the 



Text-fig. 25. 

 A single areole from the wing of M<rope tiilx r Newni., to show the Irichi- 

 ation; ( x 100). Note the absence of luacrotrichia from the two 

 cross- veins bounding the aieole. 



wiiK^ while those left in the more distal areas become, for the 

 most part, very regularly arranged in rows parallel to the main 

 veins. In the Naivnochoristida'^ we see a further stage of reduc- 

 tion reached, the macrotrichia being here entirely absent from 

 the membrane of the hindwing: while, in the forewing, they only 

 remain upon the anterior portion of the pterostigma. Finally, 

 in the highly specialised Bittacidce, all the macrotrichia have 



