120 HABITS AND INSTINCTS OF ANIMALS. GHAP. IV. 



when adult, according to .our own observations, in 



37 



variably fly at the same time. There is, however, a 

 whole family of little beetles (HalticicUe, 

 fig. 38.) which make as prodigious leaps 

 as the flea, which they resemble so much 

 in size and colour, that the species in- 

 digenous to this country are known to 

 the farmers of some districts by the same 

 name as their prototypes: their hinder 

 thighs (a), in conformity with this habit, 

 are of a most disproportionate strength 

 and thickness, appearing as if swollen. 



Among the apterous class, we have also several genera 

 39 of leapers, such as the 

 Podura, or spring-tail 



(fiff- 39-X and a wh <>le 

 division of crustaceous 

 insects, which abound 

 under sea-weed on almost every shore, and are fami- 

 liarly known by the name of sand fleas. 



(142.) The different flights of insects would fill a 

 volume with a subject we can here but slightly glance 

 at. In point of celerity, many insects fly much quicker 

 than any birds, when we take into account their very 

 inferior size. It has been calculated that the common 

 house fly, in its ordinary flight, makes with its wings 

 about 600 strokes, which convey it five feet, every 

 second. But, if alarmed, their velocity can be increased 

 six or sevenfold, or to thirty or thirty-five feet in the 

 same period. * 



* Int. to Ent. voL ii. p. 362. 



