ODONA TA 



319 



By comparing the figure of the wing of an adult (Fig. 364) with 

 that of the full-grown naiad (Fig. 363), it will be seen that the 

 oblique vein marked o is not a cross-vein but a section of vein Rs ; 

 so too, what appears to be another cross-vein, labeled 5 n, is also a 

 section of vein Rs; this section of vein Rs is known as the subnodus. 

 It will also be seen that what appears to be the base of the radial 

 sector, labeled 6 r, is a secondarily developed vein which connects the 

 radial sector with a branch of media ; this secondary vein is known 

 as the bridge. The beginning of the formation of the bridge is shown 

 in Figure 363.* 



The more important of the other special terms used in descriptions 

 of the wings of dragon-flies are the following : Much use is made in 

 taxonomic work of the two series of cross-veins that are nearest the 

 costal margin of the wing ; those of these cross-veins that are situated 

 between the base of the wing and the nodus are termed the antenodal 

 cross-veins; the first of these two series of antenodal cross-veins ex- 

 tend from the costa to the subcosta; the second from the subcosta 

 to the radius; the antenodal cross- veins are termed the antecubital 

 cross-veins by some writers. The two series of cross-veins nearest to 

 the costal margin of the wing and between the nodus and the apex 



of the wing are termed 

 the postnodal cross- 

 veins; the first of the 

 two series of postnodal 

 cross-veins extend 

 from the costa to vein 

 Rr, the second, from 

 vein Ri to vein Mr, 

 the postnodal cross- 

 veins are ternied the 

 postcubital cross-veins 

 by some writers. Near 

 the base of the wing 

 there is in dragon-flies 

 a well-marked area of 

 the wing, which is usu- 

 ally triangular in out- 

 line (Fig. 364, t); this 

 is the triangle; ire-^'f 366.-Exuvi^ 

 ^1 ,1 , ^. ' . . of a naiad of a drag- 

 quently the triangle is on-fly, Tetr ago- 

 divided by one or netiria. 

 Fig. 365. -Hind-intestine and part more cross-veins into 

 of the tracheal system of a naiad two or more cells. The area lying imme- 

 oi^schnacyanea: R, R, R, R,vec- diatcly in front of the triangle (Fig. 364, 



s) is termed the supertriangle; like the 

 triangle this area may consist of a single 

 cell or may be divided by one or more 



turn; A, anus; id, dorsal tracheal 

 tubes; /z', ventral tracheal tubes; 

 M, Malpighian tubes. (From 

 Sharp, after Oustalet.) 



*The conclusions regarding the homologies of the wing- veins given here are 

 based on investigations by Dr. Needham the results of which were published by 



