. Elementary entomology. Insects. 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 , though often brilliantly marked with metallic blue, green
. Elementary entomology. Insects. 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 , 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 face anc[ gives 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 nymphs of 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 a
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