ulgence is
sought for whatever imperfections or deficiencies may appear. Our
systems of classification may at least be tested by the application of
the theory of evolution. The natural system, if we mistake not, is the
genealogy of organized forms; when we can trace the latter, we establish
the former. Considering how much naturalists differ in their views as to
what is a natural classification, it is not strange that a genealogy of
animals or plants seems absurd to many. To another generation of
naturalists it must, perhaps, be left to decide whether to attempt the
one is more unphilosophical than to attempt the other.

Most of the cuts have already appeared in the "Guide to the Study of
Insects" and the "American Naturalist," where their original sources are
given, while a few have been kindly contributed by Prof. A. E. Verrill,
the Boston Society of Natural History, and Prof. C. V. Riley, and three
are original.

SALEM, June, 1873.

OUR COMMON INSECTS.

INTRODUCTORY.

_What is an Insect?_ When we remember that the insects alone comprise
four-fifths of the animal kingdom, and that there are upwards of 200,000
living species, it would seem a hopeless task to define what an insect
is. But a common plan pervades the structure of them all. The bodies of
all insects consist of a succession of rings, or segments, more or less
hardened by the deposition of a chemical substance called chitine; these
rings are arranged in three groups: the head, the thorax, or middle
body, and the abdomen or hind body. In the six-footed insects, such as
the bee, moth, beetle or dragon fly, four of these rings unite early in
embryonic life to form the head; the thorax consists of three, as may be
readily seen on slight examination, and the abdomen is composed either
of ten or eleven rings. The body, then, seems divided or _insected_ into
three regions, whence the name _insect_.

The head is furnished with a pair of antennae, a pair of jaws
(mandibles), and two pairs of maxillae, the second and basal pair being
united at their base to form the so-called labium, or under lip. These
four pairs of appendages represent the four rings of the head, to which
they are appended in the order stated above.

A pair of legs is appended to each of the three rings of the thorax;
while the first and second rings each usually carry a pair of wings.

The abdomen contains the ovipositor; sometimes, as in the bees and
wasps, forming a sting. In th