CH. XI.] ACARI MITES AND TICKS. 203 



Sparrman asserts, that he found several acari, of 

 the largest dimensions, on three rhinoceroses re- 

 cently killed ; and that when these were gorged with 

 blood, they became distended to an enormous size. 



Birds are infested with acari : the domestic fowl, 

 the sparrow, the peacock, are worlds for minuter 

 creatures, which attack them as parasites, like the 

 species already mentioned. Some others of this fa- 

 mily, besides having their extremities terminating in 

 bladders, capable of being inflated and contracted at 

 will, are furnished with a crotchet or hook, on the 

 under part of each bladder. This mechanism ren- 

 ders it extremely difficult to dislodge them when they 

 have once settled. Not only man, and the giants of 

 the creation, whether vegetable or animal, are sub- 

 jected to the attacks of these tiny depredators, but 

 insects themselves must furnish nourishment to still 

 smaller insects; and even the smallest of those 

 which are visible to the naked eye, present a wide 

 range for some puny parasite. The bee, the beetle, 

 and the dragon-fly may be seen covered by these 

 creatures. The spider, at all times offensive, be- 

 comes loathsome when its body is eaten up with 

 acari. The common fly must yield up its juices to 

 its parasites, and the gnat which steals a minute drop 

 from man, provides an ocean of nourishment for the 

 little hexapodes, which lodge under the ample folds 

 of its body. The minute plant-lice, which drain the 

 vegetable world, are themselves drained in their turn. 

 But there are some species of insects, which are in- 

 fested by acari whose habits are perfectly unique. 

 De Geer observed a heap of small acari piled on the 

 body of a species of beetle (leptura), which prevented 

 it from walking, and appeared to inflict upon it the 

 greatest torment. On examining this heap with a 

 lens, what was his astonishment in discovering that 

 the acari composing it formed a chain of suckers ! 

 The first sucked the leptura, the second sucked the 

 sucker, and the third drained the second. Each of 



