ODONATA 



53 



The abdomen is wide 

 includes a large gill 



for capturing prey, and that is altogether unique and 

 peculiar to this order. All are aquatic and breathe by 

 means of gills. 



The nymphs of dragonflies are stout-bodied, rather un- 

 attractive, stiff-legged creatures, that usually lie among the 

 water weeds or in the bottom 

 silt, 

 and 



chamber in which the ali- 

 mentary canal terminates. 

 There are no external gills. 

 These nymphs can swim 

 rather jerkily by successive 

 expulsions of water to rear- 

 ward out of the gill chamber. 



The nymphs of damselflies 

 are slender, long-bodied, 

 lank-legged creatures that 

 cling to water weeds. The 

 abdomen is narrow and bears 

 on its tip three flat gill plates 

 placed side by side with 

 edges vertical. They swim by 



sculling with these gill plates, swinging the tip of the ab 

 domen slowly from side to side. 



Fig. 19. — Three selected instars in the 

 nymphal life of the "Big Green Darner" 

 dragonfly, Anax Junius', A, new hatched; 

 B, one-fourth grown; C, half grown. Such 

 color changes are uncommon in this order. 



