CH. XI.] ACARI MITES AND TICKS. 201 



produces a little vesicle from whence it never moves. 

 An experienced eye will readily detect its lurking 

 place, and an experienced hand as readily remove it 

 with the point of a pin. If it be placed on the nail 

 it remains immoveable until wanned by the breath, 

 when it runs with great agility. 



Almost all the vegetable and animal matter used 

 by man is infested by some species of this insect: 

 dried meat, old bread, flour, sweetmeats, cheese, 

 Boon swarm with an extremely minute and active 

 ra^e of mites, any of which, when viewed with the 

 microscope, appear covered with hair ; and, Avhat is 

 curious, each hair is as moveable as the quills of the 

 porcupine : consequently in an animal invisible to 

 the naked eye, it is probable that each hair has a 

 muscle attached to it. These insects multiply both 

 in winter and summer, and as they arrive at perfec ■ 

 tion in a week, it may be imagined what myriads 

 must be generated. In fact, to these little creatures 

 is intrusted the task of clearing away much of the 

 dead matter which would otherwise annoy us. As 

 hey are imperceptible, says Latreille, an infinite 

 number must enter into the bread we eat, especially 

 if it be made of old flour. 



Our domestic quadrupeds furnish a lodging for 

 acari. They appear, in the first instance, to be ge- 

 nerated in the woods, and whenever the dog, the ox, 

 or even man, comes into contact with them, they 

 bury their trunk in the skin, and suck the blood with 

 avidity. 



Their body is smooth, and their shape a little oval 

 sac or cup, — a reservoir for the vital fluid. The 

 trunk or pump is furnished on each side with a set of 

 teeth like those of a saw, and it is by means of the 

 hold these afford that the acarus is enabled to 

 fix itself so firmly. The mite known to the older 

 naturalists by the name of reduvius fixes itself to 

 cattle and sheep, by a similar trunk, the teeth of 

 which are turned backwards. These, 1 ike several of 



