904 THE AMERICAN NATURALIST. (Vor: XXXII. 
way, and a single anal vein with three branches, which may 
represent the three anal veins, fused at the base. 
At B (Fig. 60) is represented the tracheation of a somewhat 
older wing, one measuring 3 mm. in length. Here the radial 
sector has shifted its position and lies across the end of the 
media, the terminal portion of it lying between Mı and M2. 
The media is now four-branched. The costal and anal trachee 
Fic. 61.— Fore and hind ppe of a nearly grown nymph of Cordulegaster Se showing 
trachez 
l, 
n”, nodus; sź, stigma; ə, hea vein; i bri west ar, , arcu cuins ria a: a 
xcept 
TR 1 
i 
anal loop. er 
here i d by dotted fan at the bridge, arculus, int shoy 
are outrun by the others in the occupation of the new territory 
formed by the growth of the wing, and remain relatively short. 
In the wings of a grown nymph (Fig. 61) is seen the culmi- 
nation of these tendencies. The radial sector has completed 
its migration and lies in its final position, the terminal portion 
traversing the area between Mz and M3. The costa is greatly 
reduced or, rather, outstripped by its competitors ; the same is 
true in a less degree of the subcosta and the anal vein. At 
this stage the veins, which are not represented in the figure, 
appear as pale, brownish thickenings ; surrounding all of the 
