THE WINGS OF NEUROPTERA 



149 



then has migrated along this cross- vein till vein R2+3 is reached. The 

 fourth diagram (Fig. 138, 4) represents an intermediate stage in this 



Fig. 139. — Wings of Sisyra flavicornis. 



switching of the basal connection of vein R4. Here the base of vein R4 

 appears to be forked, one arm of the fork arising from vein R5, and the 

 other from vein R2+3. The former is the true base of vein R4, the latter is 

 a cross-vein which is assuming the function of a base of this vein. An 



/si A Ciii 

 Fig. 140. — Fore wing of a pupa of Chanliodes pecticornis (After C. & N.). 



example of this condition of the base of vein R4 exists in the wings of 

 Uhilodes hyalina (Fig. 142). 



The fact that the base of a vein can be switched from one support to 

 another is shown by the fore wing of a specimen of Neuroptynx appendicula- 



