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 

 chlique vein marked o is not a cross-vein but a section of vein R?; 

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

 section of vein Rg; 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 b r, isa 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 b}^ 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 

 R] ; the second, from , 

 vein Ri to vein Mr, 

 the postnodal cross- 

 veins are teimed the 

 postciibital cross-veins 

 by some writers. Near 

 tlie 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; fre- . ■ ^ t a 



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

 quently the triangle is ^j^.f iy_ Tetrago- 

 divided by one or neuHa. 

 Fig.365.-Hind-intestineand part more cross-veins into 

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

 ot /EscJmacyanea: R, R, R, R,vec- diatelv in f ront of the triangle (Fig. 364, 

 rif,;.T„\vS^tctaUubS! f.'' terrnedthe ™f.rt™„gfe; like the 

 M, Malpighian tubes. (From triangle this area may consist of a single 

 Sharp, after Oustalet.) cell or may be divided by one or more 



Fig. 366. — • Exuviae 



*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 



