nch in length. We have received it from Missouri, at the hands of
Mr. Riley, and Mr. J. A. McNiel has found it very abundantly on horned
cattle on the western coast of Nicaragua.

We now come to the genus Acarus (Tyroglyphus), of which the cheese and
sugar mites are examples. Some species of Acarian mites have been found
in the lungs and blood-vessels, and even the intestinal canal of certain
vertebrates, while the too familiar itch insect lurks under the skin of
the hand and other parts of the body of certain uncleanly human bipeds.

[Illustration: 148. Sugar Mite.]

Many people have been startled by statements in newspapers and more
authoritative sources, as to the immense numbers of mites (Acarus
sacchari, Fig. 148) found in unrefined or raw sugar. According to Prof.
Cameron, of Dublin, as quoted in the "Journal of the Franklin
Institute," for November, 1868, "Dr. Hassel (who was the first to notice
their general occurrence in the raw sugar sold at London) found them in
a living state in no fewer than sixty-nine out of seventy-two samples.
He did not detect them in a single specimen of refined sugar. In an
inferior sample of raw sugar, examined in Dublin by Mr. Cameron, he
reports finding five hundred mites in ten grains of sugar, so that in a
pound's weight occurred one hundred thousand of these little creatures,
which seem to have devoted themselves with a martyr-like zeal to the
adulteration of sugar. They appear as white specks in the sugar. The
disease known as grocer's itch is, undoubtedly, due to the presence of
this mite, which, like its ally the Sarcoptes, works its way under the
skin of the hand, in this case, however, of cleanly persons. Mr. Cameron
states that "the kind of sugar which is both healthful and economical,
is the dry, large-grained and light-colored variety."

Closely allied to the preceding, is the Cheese mite (Acarus siro Linn.),
which often abounds in newly made cheese. Lyonet states that during
summer this mite is viviparous. Acarus farinae DeGeer, as its name
indicates, is found in flour. Other species have been known to occur in
ulcers.

[Illustration: 149. Mange Mite.]

We should also mention the Mange insect of the horse (Psoroptes equi,
Fig. 149, much enlarged; _a_, head more magnified). According to Prof.
Verrill it is readily visible to the naked eye and swarms on horses
afflicted with the mange, which is a disease analogous to the itch in
man. It has a soft, depressed body, s