202 NATURAL HISTORY. [CH. XI 



their tribe, have a sort of vesicular enlargement on 

 their feet : this bladder seems to be moved in various 

 directions, and assumes various shapes ; and as the 

 animal can fix itself or walk upon the most polished 

 mirror, it is not improbable that they effect their ob- 

 ject, after the manner of the fly, by exhausting the air. 

 The woods of the southern provinces of both the 

 Americas are infested by a species of acarus, which 

 proves a terrible pest to man and beast. They who 

 sit down on the stumps of trees, or heaps of dried 

 leaves ; they who happen to walk barefoot, are soon 

 covered with little slow-moving creatures, which, 

 fixing on the naked skin, suck the live blood, and 

 become distended to the size of half an inch in length, 

 and a quarter of an inch in height and breadth. They 

 swarm in such multitudes on cattle, and inflict such 

 wounds, that these often perish. At first the sensa- 

 tion is scarcely perceptible, afterward a pleasant 

 itching comes on ; which is succeeded by acute pain. 

 If the part be examined, the insect will be found half 

 buried in the flesh, and its place marked by a swell- 

 ing of the size of a pea. In endeavouring to ex- 

 tract this pest, the utmost care must be used ; for it 

 will sooner be pulled asunder than loose its hold ; and 

 should this accident happen, the portion of the insect 

 which is left in the skin will cause a deep and ill- 

 conditioned sore, accompanied with intolerable itch- 

 ing, which, it is said, has sometimes rendered it in- 

 dispensable to amputate the limb. Kalm says he has 

 seen them fixed to the bellies of horses, in such num- 

 bers, that the point of a knife could not be insinu- 

 ated between any two tumours, and the wretched 

 animals, after being drained and weakened, died in 

 the greatest tortures. He adds, that, like leeches, 

 when they have sucked their fill, they will drop off; 

 having taken two of these, and enclosed them in a 

 box, he found that they began to lay, and he counted 

 upwards of a thousand eggs, which each had depo- 

 sited, and still they had not finished. 



