AKU'I \ I IONS "I \'.M \ I I' 





. ul the water, while tin- hair- fall l>a< n the 



tance >f the water, as the I.-/ la being dniwi, I. The hind 



^o. Transverse sections of (A) Hydrophilus and (B) Notonecta. e, elytron; h, 

 hemelytron; /, metathoracic leg. 



legs, being nearest the center of gravity, are of most use in swimming, 

 though the second pair also are used for this purpose; indeed, a terrestrial 

 insert, finding itself in the 

 water, instinctively relies 

 upon the third pair of legs 

 for 1 ocomotion. Hydro- 

 philns uses its oar-like legs 

 alternately, in much the 

 same sequence as land 

 ts,*but Cybister and 

 other Dytiscidae, which 

 are even better adapted 

 than Hydrophilus for 

 aquatic locomotion, move 

 the hind legs simultane- 

 ou sly, and therefore can 

 swim in a straight line, 

 without the wobbling and 

 less economical move- 

 ments that characterize 

 Hydrophilus. 



Larvae of mosquitoes PlG . 23I . -Left hind legs of aquatic beetles. A. 



propel themselves by Hydrophilus triangularis; B, Cybister fimbriolatus; c, 



e , , . coxa; /, femur; s, spur; t, tarsus; ti, tibia; tr, tro- 



means of lashing, or undu- chanter. 



la t.ry, movements of the 



abdomen. A peculiar mode of locomotion is found in dragon fly 



nymphs, which project themselves by forcibly ejecting a stream of 



- from the anus. 



