MOSQUITOES, SILKIVORMS, AND DRAGON-FLIES 25 



intestine. Water, carrying air dissolved in it, enters 

 through the anal opening at the posterior tip of the body, 

 and, after giving up its air to the gills inside, is ejected 

 again. The opening is guarded by some flaps which may 

 be seen to open and close occasionally. If a nymph be 

 taken out it may eject water with considerable force from 

 this opening. 



Kill a nymph in a killing-bottle and examine it care- 

 fully. Note the wing-pads ; note the long, strong legs ; 

 also the large head with conspicuous compound eyes and 

 short delicate antennae. Examine especially the mouth- 

 parts, and note how the long under lip is folded over the 

 niouth-opening, but can be unfolded and extended from a 

 third to half an inch ; note the two grasping parts at its tip 

 (fig. 13). This long, grasping under lip is the prey-catch- 

 ing organ of the nymph, while the pair of strong jaws 

 which open and shut laterally are the organs which crush 

 the body of its prey and force its blood into the hungry 



Fig. 13. — Young (nymph) dragon-fly, showing lower lip folded and 

 extended. (From Jenkins and Kellogg.) 



mouth of the destroyer. Make a drawing of a nymph 

 from dorsal view, with its under lip extended and pinned 

 out. Make a drawing of the front of the head, with the 

 under lip folded like a mask over the face. 



The transformation to winged stage. — During the 

 life of the nymph it grows and develops from a very 

 small creature without wing-pads to a much larger one 

 with conspicuous pads. During this growth it moults 

 several times, iust as the crrowins^ silkworm does. Imme- 



