234 THE WINGS OF ODONATA 



of veins in this order (see table at the end of this chapter) . But for the sake 

 of uniformity with descriptions of the intercalary veins of other orders, and 

 because the intercalary veins are not primarily branches of principal veins, 

 I have not used the term sector in this connection. 



The supplements. — In many of the Odonata there exists in the broader 

 areas of the wings secondary longitudinal veins of an adventitious nature ; 



Fig. 236. — Wings of Anax Junius. 



these were termed supplements by Needham ('03). The supplements are 

 developed independently of tracheae and may extend in a direction more or 

 less transverse to that of the intercalary veins. 



Five supplements have been named; two of these are shown in the 

 wings of Anax Junius. One, which is situated behind the radial sector, is 

 the radial supplement (Fig. 236, rspl); the other, which is situated behind 

 vein M4, is the median supplement (Fig. 236, mspl). 



The third supplement is well-shown in the wings of Orlhemis; this 

 occurs in the area Mi and resembles the two supplements just described; 

 it is termed the apical supplement, Fig. 240, aspl. The fourth is the 

 trigonal supplement; this starts from the outer side of the triangle and 

 extends outward; it is, as a rule, less definite than the radial and median 

 supplements, being more obviously the result of a straightening out of the 

 zigzag line between two rows of cells. Sometimes it joins the median 

 supplement; in other cases, there is one row of cells between its distal part 

 and the median supjDlement; both conditions exist in the wings of Boyeria 

 irene (Fig. 237, x, x)\ the fomicr in the hind wings; the latter in the fore 

 wings. 



