ORDER Il. OF TRACHEARLE. 269 
parasites upon the skin and in the flesh of different animals, often greatly 
weakening them by their excessive multiplication. The origin of certain 
diseases is attributed to them. Other sorts of mites are also found upon 
insects; and many beetles, which subsist upon cadaverous substances, are 
often entirely covered with them. They have even been observed in the 
brain and eyes of man. ‘The mites are oviparous, and exceedingly prolific. 
Many of them are born with only six feet, and the two others are devel- 
oped a short time afterwards. It has been asserted that they produce 
the disease called ¢tch, by insinuating themselves beneath the skin. This, 
however, is an erroneous opinion. ‘They are found, it is true, in the pus- 
tules of the itch, as a resu/é of the disease, and not its cause. They are 
created, and make their appearance, only after the pustules are formed. 
A, Domesticus. —The most of these animals are very small, or almost | 
microscopic. They occur everywhere, some being of a wandering character, 
and to be found under stones, leaves, the bark of trees, or in provisions, as 
meal, cheese, pepper, &c. ; others are stationary and parasitic, on the skin of 
various animals, sometimes proving of serious injury to them. The mites in- 
habiting cheese are so minute, that, to the naked eye, they appear like moving 
particles of dust. They are very quick-sighted, and when once they have been 
touched with a pin, it is curious to observe the cunning which they display to 
avoid a second touch. They are extremely voracious, and will even prey on 
each other, and are so tenacious of life that they have been kept alive for many 
months between the object-glasses of a microscope. The species which is 
found in meal occasions considerable injury. Leuwenhock states that they 
may be expelled by placing a few nutmegs in the vessel or sack containing 
the meal. A German writer, named Funke, advises a cheaper remedy, 
which consists of the decorticated, thick branches of the lilac, or elder, 
which are to be put in the flour, and will, it is said, completely prevent 
their depredations. 
Ixopres. — This genus comprises the Ticks. They have no perceptible 
eyes; the palpi are in the shape of valves, dilated at the tip, serving as a 
sheath’ to the sucker, of which the parts are horny and toothed; the body is 
clothed with a corneous skin, or at least with a scaly plate in front. These 
ticks are parasites, sucking the blood of various vertebrated animals; and, 
although at first very much flattened, they acquire, by suction, a very large 
size, and become swollen out like a bladder. They are round or oval. 
They are found in thick woods, abounding in brushwood, briers, &c., at- 
taching themselves to low plants by the two fore legs, extending the other 
feet. They fasten upon dogs, cows, horses, and other quadrupeds, and even 
upon the tortoise, burying their suckers so completely in their flesh that they 
can hardly be detached by force, and by tearing away the portion of skin 
NO. XVIII. 87 
