562 



THE PANORPOID COMPLEX, 111., 



As in the Mecoptera, this last stage has become, for recent 

 Trichoptera, the dominant condition throughout the Order. 

 (Text-fig. 42, c, d.) 



Text-Fig. 42. 

 Evolution of the cubito-median Y-vein in Trichoptera'. a, b, c, d, 

 successive stages in its reduction, leading to strong fusion of Cui 

 with Mj—4, as in d; e ,/, stages in its lengthening; g, the same stage 

 as in b, from Rhyacophila dor sails Curtis, enlarged to show the dis- 

 tribution of the macrotrichial sockets. Lettering as on p. 535. 



[Not enough is known of the condition of the Y-vein in the 

 Triassic Paratriehoptera to furnish evidence of appreciable value 

 in this discussion. The only genus in which it is partially 

 preserved is Aristopsyche (28), in which it would appear that 

 M 1—4 was already partially fused with Cuj.] 



(3) The Lepidoptera. 



In this Order, the original condition of the Y-vein may be 

 seen complete in many of the Micropterygidae, as already de- 



