DRAGON-FLIES 



419 



never have the body so elongate as the perfect Insect, the differ- 

 ence in this respect being frequently great, and the nymphs of 

 the subfamily Libellulinae being very broad (Fig. 266, nymph of 

 Ictinus sp.) ; consequently the creature on emergence from the 

 nymph -skin is very much shorter than it will soon become. 



FIG. 265. Larva of Diplax just hatched, n, 

 a ganglion of the ventral chain ; d, dorsal 

 vessel ; x, tracheal network round rectum. 

 (After Packard, P. Boston Soc. xi. 1868, 

 p. 365.) 



FIG. 266. Ictinus sp., nymph, Hima- 

 laya. A, Dorsal, B, lateral view. 

 (After Cabot.) 



Extension begins to take place almost immediately ; it has been 

 thought by some that this is accomplished by swallowing air ; 

 this is, however, uncertain. At first the wings have only the 

 length of the wing-pads of the nymph, and their apical portion 

 is an unformed mass. The colour of the perfect Insect is not 

 present when the emergence takes place. The wing grows 

 quickly until the full length is attained. In the genus Agrion 



