210 



FIELD ZOOLOGY. 



while the female is on the wing. The female poises just 

 above the surface of the water, occasionally dipping down 

 as an egg is discharged; or from her flight she swoops 

 down at the instant of depositing the egg. The eggs are, 

 by some species, deposited free in the water, while others 

 deposit them in the stems of water plants, the slit in the 

 stem being made by the sharp ovipositor. The time of 

 hatching of the egg varies with the species and with the 



FIG. 87. Stages in development of a dragon fly, Libellula pulchella. 

 nymphal skin; B, imago. (Slightly reduced. Folsom.) 



A, last 



season of deposit. The eggs of some of the dragon flies, 

 laid in midsummer, hatch in a few days, six to ten, while 

 eggs laid in autumn do not hatch until the following 

 spring. 



From the eggs hatch tiny nymphs with slender legs, 

 thin bodies, and ho wings, of course. These nymphs are 

 aquatic throughout their long life ; hence their respiratory 

 system is adapted for breathing under water, being a 

 curious internal modification of the alimentary canal 

 at the anal end of the body. Their food consists of other 

 forms of aquatic life, mosquito eggs, larvae, pupae, and 



