128 MOVEMENT 



In insects the vibrations of the wings are untiring, and they 

 maintain a uniform and amazing rapidity. A fly's wing 

 vibrates 330 times a second, that of a bee 190 and that of a 

 wasp 110. The strength of insects is also astounding. A bee 

 can and does hft and carry 25-3 times its own body- weight, 

 whereas a man can only lift and carry about the weight of his 

 own body. 



One of the best known jumping animals is the common flea. 

 It has extremely powerful legs borne on projections sticking 

 out from the sides of the body. Fleas do not jump anything 

 like the height or length that you think they do when you are 

 trying to catch them. The present record is held, like so many 

 records, in California, by a Californian flea whose high jump 

 amounted to 7| inches and long jump to 13 inches. I have 

 recently had nine fleas weighed in a chemical balance by 

 an expert. The average of the nine came to 0-38 mgm. An 

 average man weighs some 70 kgm. Hence if a man had the 

 same leaping power as a flea he could cover 36,800 miles in 

 a horizontal jump, Ij times round the world. Vertically he 

 could leap 21,900 miles. He could leap to the moon in about 

 ten jumps. But of course this could never really happen, 

 for the velocity of the athlete would be so terrific that he 

 would burst into flame and disappear like a meteor in a cloud 

 of glory. Kangaroos and jerboas are further instances of 

 animals that progress by leaps and bounds. 



Flight 



When we come to the air we find two dominant groups 

 which have captured that realm of Nature, the insects and 

 birds. But by no means all insects fly. Neither the flea nor 

 the louse nor the bed-bug has wings ; yet all of them have an 

 uncanny power of getting where they want. 



Many other insects are devoid of wings, and either run about 

 on their legs or, as in the case of the spring-tails, proceed by 

 jumping. But the great majority of insects have gauzy wings 

 which enable them to make considerable flights. Owing to 

 its importance as a disease carrier the flight of the common 

 house-fly has been carefully studied. Marked flies have been 



