190 



THE STUDY OF FRESH-WATER ANIMALS. 



than others, flattened and fringed with hairs, acting as 

 paddles (Fig. 75). 



The water bugs, Corixa and Notonecta, have the hind pair 

 of legs greatly enlarged, flattened, and fringed with hairs, 

 forming very effective swimming organs. These are the 

 chief locomotor organs in each. In Notonecta the middle 

 pair is not used in swimming, but in mooring the insect or 

 in clambering amongst weed. In Corixa all the legs are 



Fig. 77. Cyclops, a common water flea. 

 The example is a female, carrying egg 

 sacs. The antennae are^used in swim- 

 ming. 



Fig. 78. Daphnia, a com- 

 mon water flea. The 

 antennae on head are 

 locomotor. 



furnished with swimming hairs, although the last pair is 

 undoubtedly the chief rowing organ. The legs of Nepa 

 are used for walking, not for swimming, Note the active 

 "doubling " movements of the legless larval gnats. Note 

 also the swimming feet of Gammarus and swimming 

 antennae of water fleas (Figs. 76, 77, 78). 



