22 



mentioned. In the Cordulecjaster'Khr and LiheUulidce the labium 

 is spoon-shaped, covering the face, the lobes broad and sub- 

 triangnlar, fitting closely against the median lobe and to each 

 other. The teeth of the opposed terminal margins are, in the 

 former family, large, acute, and interlocking, but in the latter 

 they are rounded crenations, at most not higher than broad. 

 These are tipped with short hairs, however, which when wet 

 make them appear pointed. On the inner surface of each lat- 

 eral lobe may be a row of several conspicuous setse, the lateral 

 seta', and a similar row on each side of the middle of the median 

 lobe — the mental seta\ The antennae are usually small and 

 cylindrical, 6- or 7-jointed, but are broad and flattened in the 

 Petal arifhe and Gomph ichf', Sind only 4-jointed in the latter family. 



The thorax and its appendages are not extensively used in 

 the classification of the nymph. On each side of the prothorax, 

 in the yEsr/uu(l(e, are a pair of small tubercles, the sapraeo.val 

 processes, best viewed in profile from above. They are fairly 

 constant in form for each species. The t((rsal jo'nits are usually 

 three in number, but in the GonipJii(l(e there are only two joints 

 in the anterior and middle tarsi. The suture between the first 

 two tarsal joints is oblique, making the basal joint much 

 shorter above than below. The comparative length of these 

 two joints, measured on the dorsal line, is a useful distinction in 

 the Lihellul}(l(('. As the suture between them is usually marked 

 in darker color above, it is easily located. The winfj-pads vary 

 in size with the age of the nymph, being at first entirely want- 

 ing. In the adult nymph four or five abdominal segments usu- 

 ally remain exposed behind them. 



The two main groups of dragon-flies are quite unlike in the 

 terminal appendages of the nymphal abdomen. In Zijgoptera 

 it ends in three large leaf-like gills, while in the Anisoptera the 

 last segment — the tenth abdominal — l)ears five small tapering- 

 appendages, which converge and form a valve closing the rectal 

 opening. The middle one above is the superior appendage, the 

 lower pair are the Inferior appendages, and on each side of the 

 superior appendage, above the inferiors, are the lateral append- 



