MUSCULAR STRENGTH OF INSECTS. 179 



though the house-fly can walk thus by causing a 

 vacuum between its feet and the glass, as we shall 

 subsequently describe at length. But the spider and 

 all caterpillars can only climb in such cases by con- 

 structing a ladder of ropes, as is represented by 

 Rosel in the instance of the goat- moth caterpillar. 



One of these caterpillars, which we possessed*. 

 made its escape in a manner much more unexpected, 

 if not so ingenious, by means of its great muscular 

 power, in which it is not a little singular that 

 insects, as Baron Hallcr remarks, appear to excel in 

 proportion to their diminutiveness. Of this we have 

 a remarkable example in the common flea, which 

 can draw seventy or eighty times its own weight f. 

 The muscular strength of this agile creature enables 

 it not only to resist the ordinary pressure of the 

 fingers in our endeavours to crush it, but to take 

 leaps to the distance of two hundred times its own 

 length; which will appear more surprising when we 

 consider that a man, to equal the agility of a flea, 

 should be able to leap between three and four hun- 

 dred yards. The flea, however, is excelled in leap- 

 ing by the cuckoo-spit frog-hopper {Tetiigonia spn- 

 maria, Olivier), which will sometimes leap two or 

 three yards, that is, more than 250 times its own 

 length J ; as if (to continue the comparison) a man 

 of ordinary stature should vault through the air 

 to the distance of a quarter of a mile. The minute 

 observation by which such unexpected facts are dis- 

 covered has in all ages been a fertile source of ridi- 

 cule for the wits, from the time when Aristophanes, 

 in his Clouds, introduced Socrates measuring the 

 leap of a flea §, up to Peter Pindar's lampoon on 



* See Insect Architecture, p. 189. 



f Haller, Physiul., vol. ix. p. 'J. 

 % De Geer, Mem., vol. iii. p. 178. 



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