THE ADULT DRAGONFLY 15 
C. Costa M. Media 
Se. Subcosta Cu. Cubitus 
R. Radius A. Anal vein 
The costa (C) is marginal, and coincides with the front border of 
the wing. It is notched in the middle at the nodus (n). 
The subcosta (Sc) ends at the nodus, and is a concave vein. 
The Radius (R) is a strong vein that parallels the two preceding, 
and appears simple; but at its base it is fused with the media as far 
as the arculus (ar), and at the nodus it gives off a strong branch to 
rearward called the radial sector (Rs).* This branch descends by way 
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Cu, 
Fig. 3. Wings of Cordulegaster sayi. 
of subnodus (sn) and oblique vein (0) to its definitive position behind 
the first two branches of the median vein, and at the point where it 
bends outward it is connected proximally by a brace, called the bridge 
(br), that appears like its true base, and that joins it again to the 
median vein. 
The media (M) is a four-branched vein. At its base it is fused with 
the Radius as just stated. The fusion is not quite complete. It has 
been compared to the union of the barrels of a double barreled gun. 
At the arculus (ar) the media descends to meet a crossvein, and then 
bends sharply outward again toward the wing margin. It gives off to 
rearward a strong branch (M;) at its departure from the arculus, and 
another (M3) just beyond, and these two branches run parallel to the 
wing margin. At the subnodus (sm) it forks, one branch (M2) running 
* Called median sector (Ms) by Tillyard: later, labelled 1R3. 
