Dragon-flies and Damsel-flies 



cast nymphal skins or exuviae, clinging here and there to stones and plant- 

 stems. Attached to these exuviae there may be often noted two or three short, 

 white, thread-like processes. These 

 are the dry chitinous inner linings 

 of the main tracheal trunks of the 

 dragon-fly which were moulted with 

 the outer body-wall. As the main 

 tracheal tubes are really invagina- 

 tions of the outer skin, it is obvious 

 that the inner lining of the trachea 

 is continuous with the outer coat 

 (chitinized cuticle) of the body-wall 

 and so is naturally cast off with it. 

 Although the habits of the adult 

 dragon-flies must be studied out of 

 doors, the nymphs can be brought 

 indoors and kept alive so that their 



walking and swimming and hiding FIG. 118. Adult and last exuvia of the damsel- 



i r j e * fly, Lestes uncata. (Natural size.) 



and capturing of prey, and often 



their transformation into winged imagoes, can be readily observed. In 

 their natural habitat some of these observations are nearly impossible, 



and for school-room or private-study aquaria 

 hardly any other animals can be found of 

 more interest to the observer, whether child or 

 grown-up, than the dragon-fly nymphs. 



Professor Needham, who has done more 

 and better work in the study of the immature 

 life of dragon-flies than anybody else, gives 

 the following directions for collecting and 

 rearing the nymphs: 



"If one wishes to collect the nymphs which 

 lie sprawling amid fallen trash, a garden-rake 

 with which to draw the trash aside, fingers not 

 too dainty to pick them up when they make 

 themselves conspicuous by their active efforts 

 to get back into the water, and a pail of 

 water in which to carry them home, are all 

 FIG. 119. A home-made water- th e apparatus required, 

 net for collecting dragon-fly "A rake will bring ashore those other 



nymphs which burrow shallowly under the 



sediment that lies on the bottom, and also a few of those that cling to vegeta- 

 tion near the surface; but for getting these latter a net is better. Fig. 119 



