Centipedes and Millipedes are collected in the same manner as spiders.
They live in damp places, under sticks and stones, and in decaying
vegetation. They should be preserved in alcohol, and on account of their
usually strong chitinous covering, precautions as to the strength of the
alcohol are less necessary here than with softer-bodied specimens.
[Illustration: FIG. 139.--A Milliped (_Cambula annulata_).]
The members of this subclass comprise a number of well-marked groups.
The Iulidae are cylindrical insects and occur in moist places, as do most
of the representatives of this subclass. A common form is represented in
the accompanying figure. The Chiliopodae comprise the flattened forms
having many-jointed antennae and but a single pair of limbs to each
segment of the body, and are the forms to which the name centipede may
properly be applied. They are predaceous in habit, live largely on
living animal matter, and are very quick in their movements. Some forms
are poisonous, having poison glands at the base of the first pair of
legs, but the majority of the species are entirely harmless. A number
of common species belong to the genus Geophilus and occur under stones
and logs. The genus Scolopendra includes some of the larger species of
the order. The largest known species, _S. gigantea_, occurs in the East
Indies and attains a length of from 9 inches to more than a foot.
Several species found within the limits of the United States attain a
length of 5 inches or more. The family Cermatiidae includes the very
common species _Cermatia forceps_, which, while abundant in the South
and West, occurs somewhat more rarely in the North. It is commonly found
in moist situations, in houses or conservatories, and on account of its
long legs and agile movements frequently creates considerable
consternation. It is, however, an entirely harmless and very beneficial
species, since it feeds on various household pests, including flies,
roaches, etc.