The insects constituting this group are distinguished by having their
hind legs adapted for walking or running. They are subdivided into
three families.
_Family 1, Blattidæ._--This family includes the numerous species of
cockroaches, or "black bats" as they are often called by uneducated
persons. They are represented in all parts of the world, but are most
abundant within the tropics, and especially in central and southern
America, where also the largest and finest species are to be found.
Many curious forms are also to be met with in India and different parts
of Africa.
They are very active creatures, and run with considerable rapidity, but
their activity is chiefly nocturnal, and during the day they generally
remain quietly concealed in some obscure retreat. Their diet consists
of both vegetable and animal matter, and offal of every description.
They are most useful in hot climates, acting the part of scavengers,
and by these means preventing the outbreak of malaria and other
pestilential diseases.
The best-known species in this country is the common Cockroach (_Blatta
orientalis_), which, by-the-bye, is not a native of Europe, having been
introduced from the East several centuries ago, and to have made its
home here.
[Illustration: Fig. 66.--Blatta Orientalis.]
Other species besides this are met with occasionally in different parts
of the country, having been introduced in like manner at different
times from foreign parts. The Giant Cockroach (_Blaberus giganteus_)
is one of these. Its native home is South America and the West
Indies, and in the latter place it is commonly called the "drummer."
It measures nearly three inches in length. The Zoological Gardens in
London is a favourite resort of this species.
[Illustration: Fig. 67.--Blaberus Giganteus.]
[Illustration: Fig. 68.--Corydia Petiveriana.]
_Family 2, Mantidæ._--The _Mantidæ_ may be at once distinguished from
the insects comprising the other two families of the _Cursoria_ by the
structure of the forelegs, which are converted into powerful raptoral
organs.
The body of these insects is more or less elongated, and the head,
which is triangular or heart-shaped, is attached to the thorax by a
distinct neck.
[Illustration: Fig. 69.--Blepharis Mendica.]
The _Mantidæ_, or Praying Insects, are celebrated for their habit of
resting on their four hind legs, and with their front legs raised in
the air, in what was formerly supposed to be an attitude of devotion,
but really in an observant attitude, and on the alert for their prey.
None of these insects are met with in the British Isles, but several
species are rather abundant in the south of France. Two species,
_Mantis pauperata_ and _Mantis religosa_, measure about two or two and
a half inches in length. A third species, _Mantis oratoria_, is also
common but somewhat smaller in size.
_Family 3, Phasmidæ._--These insects very much resemble the _Mantidæ_
in general appearance, to which also they are very closely allied.
They are among the most peculiar insects in existence. Their appearance
is comical in the extreme. Many of them resemble sticks, either green
growing trees or brown and withered branches, and hence the name of
stick insects commonly applied to them is very appropriate. On account
of their skeleton-like forms they have also been likened to ghosts and
spectres.
Some few species mimic leaves of trees and various plants, and these
are often called "leaf insects."
The number of species of this family is not very large, and by far the
greater part of these are inhabitants of the warmer regions of the
earth, and they seem to increase in size, especially the nearer their
home lies to the Equator.
Among the more interesting species we may mention _Cyphocrania
semirubra_ from Brazil, with short greenish elytra and pink wings.
_Bacillus rosii_ is a brown, wingless form found in Italy and the south
of France.
Some of the tropical species are among the largest insects known. A
winged Australian species attains the length of ten inches.
_Lopaphus cocophagus_ is a common species in the South Sea Islands, and
sometimes commits great ravages in the plantations of cocoa-nut trees.
When this insect is alarmed it squirts out a highly acrid fluid, which
causes great pain, and sometimes blindness if it reaches the eye.
We may remark that no species of _Phasmidæ_ are known to inhabit the
British Isles.