THE DRAGON FLY'S MASK. 



109 



This mask (Fig. 127) is peculiar to the young, or larva and pupa 

 of the Dragon fly. It is the labium, or under lip greatly 

 enlarged, and armed at the broad spoon-shaped extremity (Fig. 

 127, x} with two sharp hooks, adapted for seizing and retaining 

 its prey. At rest,' the terminal half is so bent up as to conceal 

 the face, and thus the crea- 

 ture crawls about, to all 

 appearance, the most inno- 

 cent and lamb-like of in- 

 sects. 



Not only does the imma- 

 ture Dragon fly walk over 

 the bottom of the pool or 



128. Abdominal valves ; a, side view. 



stream it inhabits, but it 

 can also leap for a consid- 

 erable distance, and by a most curious contrivance. By a 

 syringe-like apparatus lodged in the end of the body, it dis- 

 charges a stream of water for a distance of two or three inches 

 behind it, thus propelling the insect forwards. This apparatus 

 b combines the functions of 



locomotion and respiration. 

 There are, as usual, two breath- 

 ing pores (stigmata) on each 

 side of the thorax. But the 

 process of breathing seems to 

 be mostly carried on in the tail. 

 The tracheae are here collected 

 in a large mass, sending their 

 branches into folds of mem- 

 brane lining the end of the ali- 

 mentary canal, and which act 

 like a piston to force out the 

 water. The entrance to the 

 canal is protected by three to 

 fi v e triangular horny valves 

 (Fig. 128,9, 10,- 128 a, side 

 129. Agrion; 6, False Gill of Larva, view), which open and shut at 

 will. When open, the water flows in, bathing the internal gill- 

 like organs, which extract the air from the water, which is then 

 suddenly expelled by a strong muscular effort. 

 In the smaller forms, such as Agrion (A. saucium, Fig. 129 -, 

 10 



