162 ZOOLOGY. [PAET II. 



armed with two sharp hooks, with elastic pads opposed to them, 

 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, it is unable to fly. 



Its strangest peculiarity, and that which gave rise to the 

 belief that it is 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 dis- 

 cernible 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 sud- 

 den jerk the Httle*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 hairs, its feet are furnished 

 with prehensile hooks that almost convert them into hands; and 

 being obliged to conform to the sudden flights of its patron, 

 and accommodate itself to inverted positions, all attitudes are 

 rendered alike to it by the arrangement of its limbs, which 

 enables it, after every possible gyration, to find itself always on 

 its feet. 



