lt Hydrachna
concharum living parasitically on the gills of the fresh-water mussel,
Anodon. The species are of minute size. Collectors of beetles often meet
with a species of Uropoda attached firmly to their specimens of
dung-inhabiting or carrion beetles. It is a smoothly polished, round,
flattened mite, with short, thick legs, scarcely reaching beyond the
body.

[Illustration: 147. Cattle Tick.]

We now come to the Ticks, which comprise the largest mites. The genus
Argas closely resembles Ixodes. Gerstaecker states that the Argas
Persicus is very annoying to travellers in Persia. The habits of the
wood ticks (Ixodes) are well known. Travellers in the tropics speak of
the intolerable torment occasioned by these pests which, occurring
ordinarily on shrubs and trees, attach themselves to all sorts of
reptiles, beasts and cattle, and even man himself as he passes by within
their reach. Sometimes cases fall within the practice of the physician,
who is called to remove the tick, which is found sometimes literally
buried beneath the skin. Mr. J. Stauffer writes me, that "on June 23d
the daughter of Abraham Jackson (colored), playing among the leaves in a
wood, near Springville, Lancaster County, Penn., on her return home
complained of pain in the arm. No attention was paid to it till the next
day, when a raised tumor was noticed, a small portion protruding through
the skin, apparently like a splinter of wood. The child was taken to Dr.
Morency, who applied the forceps, and after considerable pain to the
child, and labor to himself, extracted a species of Ixodes, nearly
one-quarter of an inch long, and of an oval form and brown mahogany
color, with a metallic spot, like silver bronze, centrally on the dorsal
region." This tick proved, from Mr. Stauffer's figures, to be, without
doubt, Ixodes unipunctata. It has also been found in Massachusetts by
Mr. F. G. Sanborn.

Another species is the Ixodes bovis (Fig. 147), the common cattle tick
of the Western States and Central America. It is very annoying to horned
cattle, gorging itself with their blood, but is by no means confined to
them alone, as it lives indifferently upon the rattlesnake, the iguana,
small mammals and undoubtedly any other animal that brushes by its
lurking-place in the forest. It is a reddish, coriaceous, flattened,
seed-like creature, with the body oblong oval, and contracted just
behind the middle. When fully grown it measures from a quarter to half
an i