IOO 



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 colore.d, 

 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 

 B 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- 



FIG. i ^o. A, part of two rows of , IIT-U i 



.. i suspecting prey. When drawn in, 



respiratory folds from cuticular 



lining of rectum of dragon-fly the labium covers the front of the 

 nymph (sEschna}. The shaded f ace anc [ gi ves the nymph an exceed- 



parts are abundantly supplied with . . , . , . 



tracheal tubes, as shown at B, a ^gly COmiCal Appearance, With its 



small part of one leaflet highly large, shrewd eyes on either side. 



magnified, showing many fine tra- The nym ph s o f the damsel-flies 

 cheal branches . . 11-11 



breathe through the tracheal gills at 



(Redrawn from Miall) . r . , i_ -i 



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 



