ANISOPTERA. 



91 



and their great compound eyes shining like gold or pre- 

 cious stones. But for all their terrible names, dragon-flies 

 are entirely innocent of any harm to mankind. They 

 neither sew up people's ears, as northern children think; 

 nor bring dead snakes to life, as colored people in the 

 South believe; but they are very fierce enemies to their 

 insect kindred. Their long, narrow, closely netted wings 

 are strong, carrying them swiftly ; and their jaws are 

 powerful, and their appetites good ; so it is an unfortunate 

 insect that falls in their way. The fact that they destroy 

 mosquitoes has attracted much attention 

 of late ; but they feed upon a great variety 

 of insects ; and the larger species habitu- 

 ally eat the smaller ones. 



The eggs of dragon-flies are laid in 

 water or fastened to aquatic plants. The 

 nymphs present a striking peculiarity of 

 the respiratory system ; very large tra- 

 cheal extend to the rectum, and their 

 branches penetrate its wall and end in 

 a complicated series of tracheal gills in 

 the cavity of the rectum. The insect 

 alternately draws water into this cavity 

 and expels it; and thus the air in these 

 tracheas is purified. This process also 

 helps the insect in swimming, for the 

 water may be expelled with such force that the whole body 

 is sent forward. The full-grown nymph leaves the water 

 to undergo its last molt ; and the exuviae are often found 

 clinging to objects near the water (Fig. 98). 



Suborder Zygoptera (Zy-gop'te-ra). 



The D anise l-fiics. 



The damsel-flies differ from the dragon-flies in that the 

 two pairs of wings are similar in form and are either folded 



Fig. 98. — Exuviae of 

 nymph of dragon-fly. 



