12 ANIMALS OF NORTH AMERICA. 



membrane which forms the wings, only a little hook, called 

 the thumb-nail, is left free. With this the animal suspends 

 itself on any rough or uneven surface where it happens to 

 alight ; while the hind feet are also provided with claws, by 

 which it hangs head downwards on the sides of chimneys, 

 hollow trees, and roofs of caverns, a favorite resort, still and 

 silent, sleeping, or perhaps nursing its young by day, till the 

 approach of evening, when it begins its excursions in search 

 of food. 



Having neither the disposition nor the power to exercise 

 themselves by day, bats are strictly nocturnal animals, com- 

 mencing their search after insects soon after the swallow has 

 quitted his operations for the day. Its motions, as it flits 

 about in the dim twilight, seldom moving more than a few 

 yards in a straight line, darting up or down, this way or that, 

 instead of being for its mere pleasure, as many would 

 suppose, are really its only means of procuring its living, 

 since at every turn it seizes, or attempts to seize, some one of 

 the insect tribe, which swarm under cover of darkness in the 

 air. While on the wing it continually utters a low shrill cry, 

 not unlike the squeaking of a mouse. 



Naturalists have long since discovered by experiments, 

 that bats deprived of sight, still avoided obstacles as perfectly 

 as those with their sight entire, flying through small aper- 

 tures only just large enough to admit them without touching ; 

 numerous small threads also were drawn across the room 

 where the experiment was made at different angles, and still 

 the blind bat would fly about in every possible direction without 

 ever touching them. The vibration of the air striking against 

 the impediment, was supposed to return a sound by which 

 the animal was warned of its direction. But it has since 

 been found that the destruction of hearing as well, made no 

 difference in the fact, and the only theory that has been pro- 

 posed to account for this curious circumstance is, that some 

 peculiar sense is lodged in the expanded nerves of the nose. 



