BY R. J. TILLVARD. 



645 



for tliis Ordei", on account of the existence of the arcliaic Rhi/- 

 phidit', an Archetype similar to tliat of the Mecoptera, but with 

 the microtrichia somewhat smaller than in that Order. 



Older TRICHOPTEHA. (Text-fios.:^(), :',1). 

 In this Order, the most archaic tj^pes, such as tlie Rhyacophil- 

 id(f, alread}' show considerable specialisation in their wing--ti'i- 

 chiation. The archedictyon is always absent, but its macrotrichia 

 are present upon the wing-membrane, and remain there, on the 

 whole with ever increasing abunrlance, as we pass to the highest 

 types within tiie Order. Microtrichia are present throughout 

 the Order, but are always small, averaging about 5//. in length. 

 Macrotricliia are present upon the main veins and their branches, 

 but never upon the few and weakly developed cross-^'eins, except 

 in the cases where the proliferation of these hairs upon the mem- 

 brane leads to a secondary invasion of all parts of the wing. 



Text-fig. 80. 

 Portion of two main veins and the included menibiane from the win^ of 

 Rhyacopltila f/o/-s«//.9 Curtis, to show the tHehiation;( x 10")). (Micro- 

 trichia are slio;litly exaggerated in this figure). 



Tn describing the macrotrichia of the Protomecoptera, we have 

 already mentioned that those found upon the archedictyon were 



50 



