THE WINGS OF CORRODENTIA 261 



The media. — The media coalesces with radius for a short distance at the 

 base of the wing; it then bends backward and joins cubitus with which it 

 coalesces for a considerable distance; it is usually three-branched in the 

 fore wings, but in Ptiloneura hidorsalis, described by Enderlein ('oo) from 

 Peru, it is eight-branched. This is a remarkable departure from the 

 almost universal method of specialization in this order; and even in this 

 genus, where accessory veins have been developed upon media, the radial 

 sector is reduced to a two-branched condition. 



In the hind wings, media is usually reduced to an unbranched condition ; 

 but in some forms it is forked. 



The cubitus. — The cubitus is quite widely separated from media at the 

 base of the wing; this is well shown in the wing of a nymph of Psocus 

 (Fig. 257); but it soon joins media, with which it coalesces for a considerable 

 distance. In the fore wing, vein Cui anastomoses with media in some 

 forms (Fig. 255), in others the two veins are connected by the medio- 

 cubital cross-vein (Fig. 258), and in other forms there is no connection 

 between veins M and Cui. Vein Cu2 is short when present; it is wanting 

 in some forms. In the hind wings cubitus is reduced to an unbranched 

 condition. 



The anal veins. — As a rule the first and second anal veins are present in 

 both fore and hind wings ; in a few genera a short third anal vein is present 

 in the fore wings. All of the anal veins are unbranched. In the fore wings, 

 the first and second anal veins usually end at the same point in the margin 

 of the wing. 



