CHAP. IV. 



LEAPING OF INSECTS. 



119 



while others, again, as the common fly, are enabled, by 

 the peculiar formation of their tarsi, or claws, to effect, 

 in an instant, what philosophers accomplish with vast 

 comparative care and labour they produce a vacuum, 

 which will allow the pressure of the atmosphere to re- 

 tain them on the plane of position.* 



(140.) Some insects run with amazing velocity. Any 

 one who has watched the proceedings of a colony of 

 ants will be aware of this. " M. Delisle observed a 

 fly, so minute as to be almost invisible, which ran 

 nearly three inches in a demi-second, and in that space 

 made 540 steps ; consequently it could take 1000 steps 

 during one pulsation of the blood of a man in health ; 

 which," adds Mr. Kirby, " is as if a man whose steps 

 measured two feet should run at the incredible rate of 



more than twenty 

 miles in a minute!" 

 Some of the swiftest 

 runners are the Ci- 

 cindelidfB (fig. 36. 

 ), and other pre- 

 dacious beetles ; 

 the former, espe- 

 cially, makes its way 

 with great rapidity, 

 from occasionally 

 using its wings; while the slowest are the Cassidts (6), 

 or tortoise beetles, apt representatives in this, as well 

 as in form, of their namesakes, the chelonian reptiles. 



(141.) The power of leaping is possessed by some 

 insects in a much higher degree than is to be met with 

 in any other class of animals, that is, if we estimate 

 the distance they leap in relation to their size. Thus*, it 

 is commonly supposed that a flea (fig. 37-) will clear, at 

 a single jump, a space equal to 200 times its own length. 

 It has been thought that a grasshopper will do nearly 

 the same, even without the assistance of its wings ; but 

 we do not believe this probable, since these insects, 



* Int. to Ent. voL ii. p. 32. 



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