242 NATURAL HISTORY. [CH. XVI. 



upon almost every elephant and rhinoceros which he 

 saw, and which he attributed to this cause. 



We have already alluded to the remarkable mode 

 of production which takes place in the Linna^an 

 genus hippobosca, the most common species of 

 whicli is known by the name of the forestfly 

 {Hipp, equina). This insect is generally found upon 

 the horse, whose blood it sucks, adhering so firmly 

 to the skin of this animal, by means of its very 

 powerful hooked claws, that it is with the greatest 

 difficulty that it can be removed. In the New 

 Forest, Hants, they are found in such profusion, 

 that upwards of a hundred individuals have been 

 taken from the flanks of a single horse. It would 

 seem that white or light-coloured horses are more 

 subject to their attacks than dark-coloured ones; a 

 remark confirmed by the stable-keepers in the 

 neighbourhood of the forest. The body of this in- 

 sect is covered with a skin of so hard a texture as 

 to resist the greatest pressure that can be applied to 

 it by the hand. This species is occasionally found 

 upon cows and dogs (indeed, GeofiTroy has termed it 

 " La Mouche-a-chien"), and, it is said, even upon 

 man himself. It has the instinct to place itself in 

 those parts of the body of the horse which are 

 most denuded of hairs ; and where it cannot be 

 reached by the mouth of the horse, as beneath the 

 belly, between the head, legs, and tail, &c. Al- 

 though incapable of causing njuch mischief, it is the 

 cause of great irritation to the animal attacked, 

 especially when it occurs in considerable numbers. 

 To the ass they are the objects of the greatest 

 dread. Their legs are elevated at the sides of the 

 body, whence they have considerable resemblance 

 to spiders : — indeed, they have been occasionally 

 termed spiderflies. They run with great agility, 

 and have the faculty of moving sidewise, or even 

 backwards, like crabs. 



It is to Reaumur and Degeer that we are indebted 



