100 



ELEMENTARY ENTOMOLOGY 



nymph has five converging, spinelike appendages at the tip of 

 the abdomen. The dragon-flies are among the swiftest fliers, dart- 

 ing here and there after small flies, and are important enemies of 

 mosquitoes. They have received many local names, such as darning 

 needles, snake doctors, etc., with which are connected many curious 



superstitions of sewing up people's 

 ears, bringing snakes to life, etc., of 

 which they are of course entirely in- 

 nocent. They are usually dark colored, 

 though often brilliantly marked with 

 metallic blue, green, and red. The 

 damsel-flies are more slender-bodied 

 and fly lazily about. The eggs are 

 laid in the water or fastened to aquatic 

 plants. From them hatch the little 

 long-legged nymphs which may be 

 found browsing in the ooze and mud 

 of any pond. Dark-colored, flat, and 

 spiny, they are hardly distinguishable 

 from the debris of the bottom. They 

 have a peculiar underlip, remarkably 

 extensile, with two powerful hooks 

 at the tip, which, when thrown for- 

 ward from the head, grasps the un- 

 suspecting prey. When drawn in, 

 the labium covers the front of the 

 face and gives the nymph an exceed- 

 ingly comical appearance, with its 

 large, shrewd eyes on either side. 

 The nymphs of the damsel-flies 

 breathe through the tracheal gills at 

 the tip of the abdomen, but the 

 dragon-fly nymphs have a peculiar way of drawing water into the 

 rectum, whose walls are very thin and lined with numerous tra- 

 chea, so that the air in the trachea is purified through the wall of 

 the rectum as if it were a tracheal gill. The water from the rectum 

 may be ejected forcibly, so as to drive the nymph suddenly for- 

 ward. When full grown the nymph crawls up on a reed or plant 



FIG. 130. A, part of two rows of 

 respiratory folds from cuticular 

 lining of rectum of dragon-fly 

 nymph (sEschna). The shaded 

 parts are abundantly supplied with 

 tracheal tubes, as shown at B, a 

 small part of one leaflet highly 

 magnified, showing many fine tra- 

 cheal branches 



(Redrawn from Miall) 



