THE MITES. 341 
pairs of short-clawed feet. Pentastoma (Fig. 309) occurs in 
the lungs and liver of man, and in horses and sheep. 
Order 4. Acarina.—The mites are degenerate Arach- 
nida, the body being oval in form, 
the head usually small, more or 
less merged with the thorax, while 
the latter is not differentiated 
from the abdomen. There is a 
slight metamorphosis, the mite 
when first hatched having but» 
three pairs of legs, the fourth 
Fig. 312.—Sugar-mite. Much Fig. 318.—Carolina scorpion (Buthus 
enlarged. Carolinianus). Natural size. 
(and last) pair being added after a moult. A typical mite, 
though above the average size of the members of the group, 
is the tick (Fig. 310, Lzodes aibi- 
pictus Pack). Closely allied to this is 
Ixodes bovis Riley, the cattle-tick 
(Fig. 311), which buries its head in 
the skin, anchoring itself firmly by 
means of the backward-pointing teeth 
of its jaws. Other examples of mites 
are the cheese and sugar mites (Fig. 
312, Tyroglyphus sacchari). The lat- 
ter appear as white specks in sugar, 
and to them is due the disease known 
as grocers’ itch. Certain mites live ie pid Cieiiter canoror- 
under the epidermis of the leaves of —~ ; 
trees, often forming galls. 
