piny beneath at the base of the
legs and on the thorax. One or both of the two posterior pairs of feet
bear suckers, and all are more or less covered with long, slender hairs.
This insect may be destroyed by the same remedies as are used for lice
and for the human itch. The best remedy is probably a solution of
sulphuret of potassium.

[Illustration: 150. Itch Mite.]

[Illustration: 151. Nose Mite.]

The itch insect (Sarcoptes scabiei, Fig. 150) was first recognized by an
Arabian author of the twelfth century, as the cause of the disease which
results from its attacks. The body of the insect is rounded, with the
two hind pair of feet rudimentary and bearing long hairs. It buries
itself in the skin on the more protected parts of the body, and by its
punctures maintains a constant irritation. Other species are known to
infest the sheep and dog. Another singular mite is the Demodex
folliculorum (Fig. 151), which was discovered by Dr. Simon, of Berlin,
buried in the diseased follicles of the wings of the nose in man. It is
a long, slender, worm-like form, with eight short legs, and in the
larva state has six legs. This singular form is one of the lowest and
most degraded of the order of Arachnids. A most singular mite was
discovered by Newport on the body of a larva of a wild bee, and
described by him under the name of Heteropus ventricosus. The body of
the fully formed female is long and slender. After attaining this form,
its small abdomen begins to enlarge until it assumes a globular form,
and the mass of mites look like little beads. Mr. Newport was unable to
discover the male, and thought that this mite was parthenogenous. It
will be seen that the adult Demodex retains the elongated, worm-like
appearance of the larva of the higher mites, such as Typhlodromus. This
is an indication of its low rank, and hints of a relationship to the
Tardigrades and the Pentastoma, the latter being a degraded mite, and
the lowest of its order, living parasitically within the bodies of other
animals.

[Illustration: Harvestman.]

FOOTNOTES:

[Footnote 8: The figure at the bottom on the left represents the adult,
fully-gorged tick.]

CHAPTER XII.

BRISTLE-TAILS AND SPRING-TAILS.

The Thysanura, as the Poduras and their allies, the Lepismas, are
called, have been generally neglected by entomologists, and but few
naturalists have paid special attention to them.[9] Of all those
microscopists who have examined Podura scale