THE DRAGON FLY'S MASK. 



109 



128. Abdominal valves; a, side view. 



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

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

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

 127, x) with two sharp hoolcs, adapted for seizing and retaining 

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

 the face, and thus the crea- 

 ture crawls about, to all 

 appeai'ance, the most inno- 

 cent and lamb-like of in- 

 sects. 



Not only does the imma- 

 ture Dragon fly wallc over 

 the bottom of the pool or 

 stream it inhabits, but it 

 can also leap for a consid- 

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

 syriuge-Iike apparatus lodged in the end of the body, it dis- 

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

 behind it, thus propelling the insect forwards. This apparatus 

 h combines the functions of 



\[ \ locomotion and respiration. 



There are, as usual, tyvo breath- 

 ing pores (stigmata) on each 

 side of the thorax. But the 

 , -^^ process of breathing seems to 

 ,; ^ be mostly carried on in the tail. 

 C'^^^^^'S^^*^ The trachea} are here collected 

 iu 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 

 five triangular horny valves 

 (Fig. 128, 9, 10, 128 «, side 

 12!). '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. sauciura, Fig. 129 -, 

 10 



