INSECTS
We now come to the second of the two great divisions of the animal
kingdom, namely, the invertebrates, which includes all those creatures
which have no bones. This division in its turn consists of a good many
classes, just as that of the vertebrates does; and among these is that
of the insects, the peculiarity of which is that they must pass through
three stages of development before they reach their perfect form,
namely: first the egg; then the grub, or caterpillar; and then the
chrysalis, or pupa.
You can easily tell an insect when you see it by remembering one or two
simple rules.
In the first place, its body is always divided into three principal
parts, which are known as the head; the thorax, or chest; and the hind
body.
In the second place, it always has six legs. Spiders have eight legs.
Centipedes and millepedes have many legs. But an insect never has more
nor less than six. And each of these limbs is made up of a thigh, a
lower leg, and a foot; while the foot itself has from two to five little
joints, the last of which usually has a pair of tiny claws at the tip.
Besides these, there are several other ways in which insects differ from
the rest of the vertebrates. We need only tell you about one of them,
however, and that is that in some form or other they always have four
wings. Sometimes, it is true, you cannot see these wings. That is
because they are not developed and cannot be used for flying. But still
they are there, and by means of the microscope it is almost always easy
to detect them.
These wings, however, take all sorts of forms. The wings of a butterfly,
for example, are very different from those of a beetle or a bee; and
because of these differences in the wings, insects are divisible into
several smaller groups, which we call orders.
BEETLES
First comes the order of the beetles. These are called
_Coleoptera_, or sheath-winged insects, because their front wings,
instead of being formed for flight, are turned into horny or leathery
sheaths, or elytra, which cover up and protect the lower pair while not
in use.
At least 150,000 different kinds of beetles have already been discovered
in various parts of the world, of which America possesses tens of
thousands; and probably quite as many more remain to be distinguished.
Of these we can only mention a few of the most interesting.
The tiger-beetles are so called because they are such fierce and
voracious insects, spending most of their time in chasing and devouring
other insects. The commonest of them is about half an inch long, and is
bright green above and coppery below. You may often see it darting about
in the hot sunshine, and if you try to catch it you will generally find
that it flies away as quickly as a bluebottle.
Ground-beetles are common in gardens. One often seen is about an inch
long, and is deep black in color, with a narrow band of violet running
round the outer edge of its wing-cases. This, too, is a creature of
prey. It cannot hurt you; but if you pick it up it will make your
fingers smell very nasty. For it can pour out from its mouth a drop or
two of a dark-brown liquid which has a horrible odor.
Then there are a good many beetles which live in streams and ponds, and
are called water-beetles in consequence. They can swim and dive very
well, and are also able to fly. Almost every night they go for long
journeys through the air. And when they want to go back into the pond
they hover above it for a moment, fold their wings, and drop into the
water with a splash. Only sometimes they fly over the roof of a
greenhouse, and mistake that for a pond; and then you can imagine the
result!
The cocktails are beetles with short wing-cases and very long, slender
bodies, which they carry turned up at the rear end. Some of them are
quite large, like the ugly black "coach-horse," but many are very small.
Indeed, most of the "flies" which get into one's eyes on warm sunny days
in England are really tiny cocktail beetles, and the reason why they
make one's eyes smart so dreadfully is that they pour out a little drop
of an evil-smelling liquid from their mouths, just like the purple
ground-beetle.
SCAVENGERS
The burying-beetles are so called because they bury dead animals. Have
you ever wondered why we so seldom find a dead mouse or a dead bird,
although these creatures must die in thousands every day? One reason is
that as soon as they are dead a couple of "scavengers" are almost sure
to come and bury them. They are big black beetles, sometimes with two
broad yellow stripes across their wing-cases, and they dig by means of
their heads, scooping out the earth from under the carcass till it has
sunk well below the surface of the ground. Then they lay their eggs in
it, come up to the surface, shovel back the earth till the dead body is
quite covered over, and then fly away. And when the eggs hatch, the
little grubs which come out from them feed upon the carcass.
Among the largest beetles are those called stag-beetles because the jaws
of the male look very much like the horns of a stag. Those of the female
are much smaller, but are so sharp and strong that they can really give
a rather severe bite. These occur in various parts of the world, and are
fond of flying slowly about on a warm summer evening, generally about
twenty or thirty feet from the ground.
The cockchafer is common everywhere in spring, and if you shake a young
birch-tree, or a hazel-bush, three or four of the great clumsy insects
will very likely come tumbling down. They are rather more than an inch
long, very stoutly and heavily built, and are chestnut brown in
color, while their bodies are drawn out into a kind of point behind. The
grubs of these beetles live underground, and do a great deal of mischief
in fields and gardens, for they feed upon the roots of the plants, and
very soon kill them.
Dor-beetles, too, are very common everywhere. You may often see them
flying round and round in great circles on warm summer evenings, making
a loud humming noise as they do so. They often blunder in at open
windows, attracted by the lamplight, and children are afraid of them,
but they can do no harm. If you catch one you will find that it is
nearly black. You will also see that its front legs are broad and
strong, and that they are set with a row of stout horny teeth. With
these legs the beetle digs, using them with such address that in the
course of an hour or two it will sink a hole in the ground ten or twelve
inches deep, in order to lay its eggs at the bottom.
The famous Scarabæus of Egypt, which in days of old some of the people
of that country used to revere, because they thought it a symbol of
immortality, is really a kind of dor-beetle.
SKIPJACKS AND GLOWWORMS
Skipjacks, too, are beetles. You may know them by their long, narrow,
glossy bodies, and by the fact that the head is hidden under the thorax,
so that you can hardly see it from above. One very odd thing about them
is that they are constantly losing their footing and rolling over on
their backs; and their bodies are so shiny, and their legs are so short,
that when they do so they cannot get up again in the ordinary manner.
But after lying still for a moment they arch themselves into the form of
a bow, resting only upon their heads and the very tips of their tails,
and suddenly spring into the air, making an odd clicking noise as they
do so. And as they fall they turn half round, and so alight upon their
feet. For this reason they are often known as click-beetles.
These insects are the parents of the well-known wireworms, which often
do such mischief in our fields and gardens, living underground
for three or even four years, and feeding upon the roots of the crops,
and of such bushes as the currant.
Then the glowworm is a beetle. Perhaps you may have seen its little pale
green lamp shining in the grass on a summer evening. The light comes
from a liquid inside the hind part of the body, the skin of which is
transparent, and forms a kind of window, so that it can shine through;
and the insect has the power of turning on its light and shutting it off
at will. The lamp of the female beetle is very much brighter than that
of the male, and while the male has both wing-cases and wings, and can
fly very well indeed, those of the female are so small that one can
hardly see them. Indeed, she looks much more like a grub than a beetle.
DEATHWATCHES AND OIL-BEETLES
Deathwatches are small brown beetles which burrow into dead wood and
call to one another by tapping with their horny heads. You may often
hear them if you happen to be lying awake at night in a room in which
there is old woodwork; and in former days people were silly enough to
think that when this sound was heard it was a sign that somebody in the
house was going to die! That is why these beetles are called
deathwatches. They are quite small, and are brown in color, with rather
long feelers and legs.
Crawling on grassy banks in the warm sunshine on bright spring days, you
may often see a number of oil-beetles. These are large bluish-black
insects which have an odd habit, if you pick them up, of squeezing out
little drops of a yellow oily liquid from the joints of their legs! This
oil has a pungent smell, and no doubt prevents birds, etc., from eating
them. You will notice that the female beetles have enormous hind bodies,
which they can hardly drag along over the ground. This is because they
contain such a very large number of eggs, thirty thousand often being
laid by a single beetle. She places them in batches in holes in the
ground, and very soon afterward they hatch, and odd-looking little grubs
with six long legs come out of them. No sooner have they left the
egg-shells than these tiny creatures hunt about for a flower
with sweet juices, which is likely to be visited by a wild bee. When
they find one, they climb up the stem and hide among the petals. Then,
when the bee comes, they spring upon it and cling to its hairy body, and
so are carried back to its nest, where they feed upon the food which the
bee had stored up for its little ones.
WEEVILS AND OTHER BEETLES
A great many beetles have a long beak in front of the head, with the
jaws at the very tip. These are called weevils, and many of them are
very mischievous. Grain of various kinds, for example, is destroyed in
enormous quantities by the wheat-weevil and the rice-weevil, while the
nut-weevil is the cause of those "bad" nuts which no doubt most of you
know only too well. The mother beetle bores a hole through the shell of
the nut while it is small, and the little grub which hatches out from
the egg she leaves inside it feeds upon the kernel, leaving nothing
behind but a quantity of evil-tasting black dust.
One of the handsomest of European insects is the musk-beetle, which you
may often find sunning itself on the trunks and leaves of willow-trees
in England in July. Often you can smell it long before you find it, for
it gives out a strong odor much like that of musk. This beetle is
sometimes nearly an inch and a half long, with long legs and still
longer waving black feelers. In color it is rich golden green with a
tinge of copper. But if you put one of its wing-cases under the
microscope, it looks like a piece of green velvet studded all over with
diamonds, and rubies, and sapphires, and emeralds, and topazes, which
seem to turn into one another with every change of light.
The grub of this beetle lives inside the trunks of dying willow-trees,
and feeds upon the solid wood.
Then there are the turnip-fleas, little black beetles with a yellow
stripe on each wing-case, which skip about just as fleas do, by means of
their hind legs. They are only too common in turnip-fields, and often do
most serious mischief, nibbling off the seed-leaves of the young plants
as soon as they push their way above the surface of the ground,
and so destroying the greater part or even the whole of the crop.
And, lastly, there are the ladybirds, common everywhere. But perhaps you
did not know that they are among the most useful of insects. The fact is
that both as grubs and as perfect insects they live upon the green
blight, or greenfly, an aphis which is terribly mischievous in fields
and gardens, and destroy it in thousands of thousands. Indeed, if it
were not for ladybirds, and for one or two other insects which help them
in their task, we should find it quite impossible to grow certain crops
at all.
[Illustration: INSECTS INJURIOUS TO AMERICAN MAPLE TREES.
BORING BEETLE (Plagionotus): 1, place where egg was laid; 2, borer
or grub in September from egg laid same season; 3, nearly fully
grown borer; 4, adult beetle (black and yellow); 5, hole through
which beetle escaped from its chrysalis in the burrow; 6, dust of
borings packed in a burrow.
MAPLE-TREE PRUNER (Elaphidium): 7, 7a, grubs or borers in burrows;
8, pupa; 9, beetle (brown).
COTTONY SCALE (Pulvinaria): 10, active young (pink); 11, adult
female scales, each concealing many eggs under the woolly mass; 12,
leaf with young scale-insects on its under side.]
EUPLEXOPTERA
Next after the beetles comes the order of the _Euplexoptera_, which
means beautifully folded wings. This order contains the earwigs. We do
not know much about these insects in the United States; but they are so
constantly spoken of in books about England, where they are numerous,
that it will be well to describe them.
Perhaps you did not know that earwigs have wings; and certainly one does
not often see these beetles flying. But nevertheless they have very
large and powerful wings, only, during the daytime, while they are not
being used, these organs are folded away in the most beautiful manner
under the tiny wing-cases. By night, however, earwigs often fly; and
when they settle, they fold up their wings most cleverly by means of the
horny pincers at the tail-end of their bodies, and then pull the
wing-cases down over them!
That is the real use of the pincers, although the earwig is able to give
quite a smart pinch with them if it is interfered with.
Another very curious fact about the earwig is that the mother insect
heaps her eggs together into a little pile, and sits over them until
they are hatched. If you turn over large stones early in the spring you
may often find a mother earwig watching over her eggs in this odd
manner, and she will allow herself to be torn in pieces rather than
desert her charge.
ORTHOPTERA
Next comes this order, the name of which means straight-winged insects,
so-called from the way in which the wings are folded. This order
contains many very well-known insects.
There is the cockroach, for example, which is so common and so
mischievous in our houses. It is often called the black beetle, although
it is not a beetle at all, and is not black, but dark reddish brown. It
is remarkable for several reasons. One is that while the male has large
wing-cases and broad, powerful wings, those of the female are very small
indeed, so that she cannot possibly fly. And another is that the eggs
are laid in a kind of horny purse, about a quarter of an inch long, with
a sort of clasp on one side. These little purses are hidden away in all
sorts of dark corners, and if you open one you will find two rows of
little eggs inside it, arranged rather like the peas in a pod.
The crickets, too, belong to this order.
Of course you have often heard the big black cricket chirping merrily
away in the fields; and in Europe they have a kind called the
house-cricket, which comes into the house, and is often spoken of as
"the cricket on the hearth" in the kitchen. It is not correct, however,
to speak of the "note" or "song" of this insect, for it is not produced
in the throat at all, but is caused by rubbing one of the wing-cases
upon the other. You will notice, on looking at a cricket, that in each
wing-case there is a kind of stout horny rib, which starts from a
thickened spot in the middle. Now in the right wing-case this rib is
notched, like a file, and when it is rubbed sharply upon the other the
loud chirping noise is produced.
The feelers of the cricket are very long and slender, and at the end of
the body of the male are two long hairy bristles, which seem almost like
a second pair of feelers, warning the insect of danger approaching from
behind. At the end of the body of the female is a long spear-like organ,
with a spoon-like tip. This is called the ovipositor, and by means of it
the eggs are laid in holes punched in the soil.
Crickets have large wings, and fly rather like the woodpeckers, rising
and falling in the air at every stroke.
Another kind of cricket lives in holes in the ground, which it digs by
means of its front legs. These limbs are formed almost exactly like the
fore feet of the mole, and for this reason the insect is known as the
mole-cricket. It is generally found in sandy fields, and scoops out a
chamber almost as big as a hen's egg at the end of its burrow, in which
to lay its eggs and where it lies, showing only its jaws and great front
legs until some small creature comes near upon which it may pounce for
food.
GRASSHOPPERS
Right here has come a mixing up of names between the English, as spoken
and written in Great Britain, and that used in the United States. When
an Englishman speaks of a grasshopper he means the related insect which
we call a cicada, or katydid, and this _we_ call a locust; but when
_he_ says "locust" he refers to what _we_ call "grasshopper."
We suspect he is nearer right than we are, who have unfortunately fallen
in with the mistake of some ignorant early settler. At any rate the
locusts of which we read in the Bible, and in books of travel in desert
regions, are all of the same race as our grasshoppers. None of the
cicada tribe could ever do so much damage.
Grasshoppers (to stick to our own name) abound in all warm countries,
especially in those which in summer, at least, are hot and dry, such as
Egypt, or Syria, or parts of India. They feed exclusively on leaves,
blades of grass, and the like, and are strong fliers; and in countries
that are favorable to them, where they are always very plentiful,
certain species sometimes become excessively abundant, and then spread
over the land, and swarm away to neighboring countries, in such immense
numbers that they devour every green leaf and every blade of grass, or
spear of grain, until they leave the ground as bare as if it had been
swept by fire.
Nor is this the worst, for wherever they go the females push
quantities of eggs down into the ground. The following summer these eggs
hatch, and the devastation of the previous year is repeated, for where
before dense clouds of flying grasshoppers descended from the sky, now
enormous armies of grubs march over the ground, climb all the plants and
bushes, and devour all that has newly sprung up.
Millions may be killed by fire or other means, but it has little effect,
and the farmers and grazers of a region so visited are all but
ruined--perhaps wholly so.
When, in the last century, men began to settle on the prairies of the
far West, they met this plague; and between 1870 and 1880 the gardens
and farms and young orchards of Kansas, Nebraska, and other western
districts, were ruined again and again. The government sent out several
of the wisest entomologists it could employ to study the insects, and
they found that these destructive red-legged grasshoppers had their home
in the dry foothills of the Rocky Mountains, especially toward the
north. They learned a great deal about the habits of the insects, and
reported that there seemed no remedy just at hand; but that the more the
West was settled and cultivated, the more grass and other food would be
provided for the grasshoppers, so that they would not have to make those
wide flights, and the more the plowing of the land and burning of
rubbish would destroy their eggs, so that gradually the pest would
become less and less, until finally it would cease to be troublesome.
This has turned out to be true, and already the fear of grasshoppers has
departed. The same thing is taking place in Egypt and some other
improving countries, which no longer suffer from the plague of locusts
as they used to do.
The wonderful walking-stick and the leaf-insects also belong to this
order. They are so marvelously like the objects after which they are
named that as long as they keep still it is almost impossible to see
them. They seem to know this perfectly well, and will remain for hours
together without moving, waiting for some unwary insect to come within
reach, for they are among the insects of prey. They are found in all the
warmer parts of the world.
Equally curious, too, is the praying-mantis, which also is very much
like a leaf. It has very long front legs, with a row of sharp teeth
running along their inner margin, and when it is hungry it holds these
limbs over its head, in very much the attitude of prayer. That is why it
is called the praying-mantis. Then when an insect comes within reach it
strikes at it, and seizes it between the upper and lower parts of these
limbs, so that the long spike-like teeth enter its body and hold it in a
grip from which there is no escape. These occur in various parts of the
world, including the warmer parts of America.
DRAGON-FLIES AND MAY-FLIES
The dragon-flies belong to another division of the _Orthoptera_.
You must know these insects very well by sight, with their long slender
bodies and their broad gauzy wings; for they are common in almost all
parts of the country, and you can hardly go for a ramble on a sunny day
in summer or autumn without seeing them in numbers. There are a good
many different kinds. Some have yellow bodies, some blue ones, and some
red ones, and the loveliest of all perhaps are the graceful demoiselles,
whose wings are rich metallic purple. You may sometimes see these
beautiful insects flitting to and fro over streams and ditches.
All the dragon-flies spend the earlier part of their lives in the water.
The grubs are very curious creatures and catch their prey in a curious
way. Underneath the head is an organ called the mask. This consists of
two horny joints, which fold upon one another while not in use. At the
end of the second joint is a pair of great sickle-shaped jaws, and when
the grub sees a victim it swims quietly underneath it, unfolds the mask,
reaches up, and seizes it with the jaws. Then it folds the mask again,
and by so doing drags the prisoner down against the true jaws, by means
of which it is leisurely devoured.
This grub swims, too, in a singular manner. At the end of its body you
will notice a short sharp spike. Now this spike really consists of five
points, which can be opened out into the form of a star; and in the
center of this star is a small round hole, which is really the entrance
to a tube running right through the middle of the body. And the
grub swims by filling this tube with water, and then squirting it out
again with all its force, so that the escaping jet pushes, as it were,
against the surrounding water, and drives the insect swiftly forward by
the recoil.
Dragon-flies are voracious, and always seem to be hungry. They feed
entirely upon other insects, and spend almost all their time in chasing
and devouring them.
The May-fly, or June-fly, also belongs to this order. One sometimes sees
it in thousands, dancing, as it were, up and down in the air toward
evening on warm spring days, in the neighborhood of water. You can
always tell this insect by the three long thread-like bristles at the
end of its body.
Most people think that this insect only lives for a single day. This,
however, is not strictly true, for in damp weather many May-flies live
for three or four days. Before they become perfect flies, however, they
have lived for nearly two years in the muddy banks of rivers and ponds,
in the form of long slender-bodied grubs. These grubs always make their
burrows with two entrances, in the form of the letter U turned sideways,
so that they can easily leave them without having to turn round.
TERMITES
The most wonderful of all the insects which belong to this order,
however, are the termites. Often these creatures are known as white
ants, and although they are not really ants, they are certainly very
much like them. In Africa they make marvelous nests of clay, which are
often twelve or fourteen feet high, and are so very large that a church,
a parsonage, and a schoolroom have been built of clay slabs cut from the
walls of a single termites' nest! These nests are made up of a wonderful
series of chambers and galleries, and in the middle is the royal cell,
in which the "king" and "queen" live. For in every termites' nest there
is one perfect male and one perfect female, which are treated with very
great respect, and have a kind of palace, as it were, all to themselves.
And the rest of the insects in the nest are either imperfect
males, which are called soldiers, or imperfect females, which are called
workers.
The "king" is quite a handsome and graceful insect, with broad and
powerful wings; and the "queen," at first, is very much like him. But
they never take more than one flight in the air, and as soon as that is
over they actually break off their own wings close to their bodies! Then
they burrow into the ground and begin to form a nest. Before long, the
workers build the palace for the royal couple; and as soon as they have
been shut up inside it the body of the queen swells to a most enormous
size, so that she can no longer walk at all. This is because of the vast
number of eggs, developing within her body, which she at once begins to
lay at the rate of many thousands in a single day. As fast as she lays
them they are carried off by the workers, which also take care of the
little grubs that hatch out from them, just as bees do.
The duty of the soldiers, as their name implies, is simply to fight, and
if a hole is broken in the side of the nest they hurry to the spot at
once, and begin to snap with their jaws at the foe. And these jaws are
so sharp and so powerful that they can really give a very smart bite.
The workers are a good deal smaller, and they have to build the nest and
keep it in repair, to find food for the grubs, and take care of them,
and wash them, and feed them, and do everything else that is necessary
for the welfare of the colony.
The grubs of these insects are fed upon dead wood, which is generally
obtained from the trunks and branches of trees. But termites are
sometimes very troublesome in houses, for they will devour the woodwork
and the furniture and the books, leaving nothing but a thin shell of
wood or paper behind them.
There are a good many different kinds of these wonderful insects, and
they are found in warm countries in all parts of the world.
The North American termites do not build great clay hills or houses
above ground, but some species make extensive galleries beneath the
surface, while others hollow out a dead stump, or the dying branch of a
tree, or even an old fence-post or telegraph pole, until it becomes a
mere sponge, with a thin outside shell.
NEUROPTERA
The _Neuroptera_, or nerve-winged insects, form an order whose
wings are divided up by horny nerves, or nervures, into such numbers of
tiny cells, that they look as if they were made of the most delicate
lace.
The caddis-flies belong to this order--brownish insects with long
thread-like feelers and broad wings, which are folded tentwise over the
body when they are not being used. They are very common near ponds and
streams, in which they pass the earlier part of their lives, living down
at the bottom in most curious cases, which cover them entirely up with
the exception of their heads.
These cases are made of all sorts of materials. Some caddis-grubs merely
fasten two dead leaves together, face to face, and live between them.
Others make a kind of tube out of grains of sand, or tiny stones, or
little bits of cut reed, all neatly stuck together with a kind of glue
which resists the action of water. But the oddest case of all is made of
tiny living water-snails, and you may sometimes see fifteen or twenty
little snails all trying to crawl in different directions, while the
grub is unconcernedly pulling them along in another!
The grubs never leave these cases, but drag them about with them
wherever they go. And when they find that their odd little homes are
becoming too small, they just cut off a little piece at the end and add
a little piece on in front, rather larger in diameter. And so they
always manage to keep their homes of exactly the proper size.
Most likely, too, you have heard of the ant-lion fly, which is a rather
large fly with a slender body and four long narrow wings, and is found
in many parts of the south of Europe, as well as in America. But the
interest lies in the grub, or "ant-lion" proper, which has a most
singular way of catching its insect victims. It digs a funnel-shaped pit
in the sand, about three inches in diameter and two inches deep, by
means of its front legs and its head. Then it almost buries itself at
the bottom, and lies in wait to snap up any ants or other small insects
which may be unfortunate enough to fall in. And if by any chance they
should escape its terrible jaws and try to clamber up the sides, it
jerks up a quantity of sand at them, and brings them rolling down again
to the bottom, so that they may be seized a second time.
A relation of the ant-lion is called the lacewing fly, and is a pretty
pale-green insect with most delicate gauzy wings, over which, if you
look at them in a good light, all the colors of the rainbow seem to be
playing; and its eyes glow so brightly with ruby light that one can
scarcely help wondering if a little red lamp is burning inside its head.
You may often see it sitting on a fence on a warm summer day, or
flitting slowly to and fro in the evening.
This fly lays its eggs in clusters on a twig, or the surface of a leaf,
each egg being fastened to the tip of a slender thread-like stalk. The
result is that they do not look like eggs at all; they look much more
like a little tuft of moss. When they hatch, a number of queer little
grubs come out, which at once begin to wander about in search of the
little greenfly insects upon which they feed. And when they have sucked
their victims dry, they always fasten the empty skins upon their own
backs, till at last they are covered over so completely that you cannot
see them at all!