Chap. L] 



NYCTERIBIA. 



21 



known insect, and as its joints are so flexible as to yield 

 in every direction (like what mechanics call a " ball and 

 socket "), its motions are ex- 

 ceedingly grotesque as it tum- 

 bles through the fur of the 

 bat. 



To enable it to attain its 

 marvellous velocity, each foot 

 is armed with two sharp hooks, 

 with elastic opposable pads, so 

 that the hair can not only be 

 rapidly seized and firmly held, 

 but as quickly disengaged, as 

 the creature whirls away in its headlong career. 



The insects to which it bears the nearest affinity, are 

 the Hippoboscidce, or " spider flies," that infest birds and 

 horses ; but, unlike them, the Nycteribia is unable to fly. 



Its strangest peculiarity, and that which gave rise to 

 the belief that it was headless, is its faculty when at rest 

 of throwing back its head and pressing it close between 

 its shoulders till the under side becomes uppermost, not 

 a vestige of head being discernible where we would 

 naturally look for it, and the whole seeming but a 

 casual inequality on its back. 



On closer examination this apparent tubercle is 

 found to have a leathery attachment like a flexible neck, 

 and by a sudden jerk the little creature is enabled to 

 project it forward into its normal position, when it is 

 discovered to be furnished with a mouth, antennae, and 

 four eyes, two on each side. 



The organisation of such an insect is a marvellous 

 adaptation of physical form to special circumstances. 

 As the nycteribia has to make its way through fur and 



c 3 



