PECULIAR MOTIOx^S OF INSECTS. 393 



others. Mr Stephens enumerates no less than twelve 

 species, from whicli it appears that those found on 

 the dog, the pigeon, and other animals, are quite 

 different from the common flea, and it is probable 

 these will not readily pass from their natural habit to 

 infest us, as is commonly believed. 



The extraordinary power of leaping in grasshoppers 

 and their congeners is matter of common observa- 

 tion. The motion is eftected by means of very 

 strong muscles with which the hind thighs are fur- 

 nished; and it is a similar structure which enables the 

 frog-hoppers (Cercopidce Leach), so common on 

 plants during summer, to perform leaps of extraor- 

 dinary extent, in which, however, they have likewise 

 the assistance of their wings. Some species make 

 use of their faculty of leaping to escape from their 

 enemies, as well as for the purpose of changing 

 place, while others use it to spring upon their prey. 

 Among the former we may mention a family 

 of small insects (Podnridm, Leach), some of them 

 inhabiting water or damp places, though most of the 

 species are found under decaying bark or vegetable re- 

 fuse. The one that is most likely to attract attention 

 is a very small gregarious one, the water spring-tail 

 {Podura aqucdica), which may often be seen, during 

 the summer, crowded upon the rain-water collected 

 in the footsteps of cattle, the ruts of cart-wheels, or 

 by the edges of small ponds, and looking precisely 

 as if one had strewed about a handful of coal-ashes 

 or gunpowder ; but, though at first glance they seem 

 inanimated, closer inspection will show that they are 

 in active motion, and particularly if they be alarmed 

 — leaping about and upon one another, f nd on the 

 water, like so many minute fire-works. Those which 

 are solitary are much larger, among which we may 

 mention the velvet spring-tail {Podura holosericca), 

 of which we here give a magnified figure, to show 



