A FROZEN WORLD 



221 



This rapid skimming in curves or circles on the 

 surface of the water is produced in a most interest- 

 ing way by the co-operation of the various pairs 

 of legs, which I can best explain by the analogy of 

 the bicycle. The two shorter and active hind-legs 

 produce the quick forward dart, just as the main 



NO. 7. THE WHIRLIGIG BEETLE IN SUMMER, DANCING. 



motion of the cycle is given it by the back wheel ; 

 the longer front legs act like the front wheel of the 

 cycle in altering the direction ; one of them is 

 jerked out to right or left, rudderwise, and gives 

 the desired amount of curve to the resulting motion 

 according to the will and necessities of the insect. 



