THE WINGS OF DIPTERA 



357 



atrophied and cells M and ist Mo arc united into a single cell, cell M + 

 ist M2. 



The anal veins. — In all Diptera known to me there is a greater or less 

 reduction of the anal area; for in none that I have seen are there present 

 three well developed anal \'eins that extend to the margin of the wing. 



Fig. 375. — Wing of Erax. 



In most Diptera the first anal vein is wanting as a distinct vein but in 

 many there is a suture-like line, the anal furrow, immediately back of 

 cubitus and closely parallel with this vein ; this is a vestige of the first anal 



Fig. 376. — A wing Eristalis. 



vein ; this furrow is represented in several of the figures in this chapter by a 

 dotted line. The first anal vein is retained, however, in certain Asilidae; 

 where, although somewhat shortened, it is a distinct vein extending from 

 the base of the wing to near the point where vein Cu forks (Fig. 375). 



id A id A 



Fig. 377. — Wing of Tipnia. 



