because he would have no other sure way of getting water to drink, and
the fish in the water, the birds on the water, and the birds' eggs in
the nests along the edge of the river offered him a sure supply of
food. And then along the river the grass grows greenest, and this
afforded good grazing for his cows, and his horses, and, may be, his
camels. What kind of food does the camel like best, anyhow? Primitive
man must have learned to swim early, and it must have been fun for the
little boys of barbarism, as it is for the little boys of civilization,
to plunge into the cooling water on a hot day. Man must have found
out very early how to make a raft which would carry him down stream,
and soon after he learned how to make a canoe that he could paddle up
stream. So the river became his first road. On it he traveled when he
went hunting, and with its help he protected his property and that of
the tribe. The enemies were driven across the river, and kept on the
other side.
A good way to study what a river does for man is to find out all you
can about the life that gathered about some particular river, for that
will tell you more or less of what happened along the banks of all the
great rivers. The best of all rivers for such study is the Nile. It
is one of the long rivers of the world, so long that its sources have
only been recently discovered by those who make geographies. Read the
stories of Livingstone and Stanley, and the early explorers, who went
in search of the head waters of the Nile.
[Illustration: A MOUNTAIN RIVER.
CHICAGO COLORTYPE CO.]
But there are two Niles. One runs through the continent of Africa, and
empties into the Mediterranean Sea. Another begins in the very earliest
dawn of history, and runs through the human story of thought, feeling,
and life. Along the banks of this Nile, in history, we see how human
life was developed; all human life beginning away back there, so far
back we cannot count it by years; when man made knives of flints and
hatchets of stone. And then, because the Nile gently overflowed its
banks two or more times a year, leaving after each freshet a soft layer
of fertile mud on either side, primitive man began to plant his seed
in this field plowed by a river, and to raise his millet, and peas,
and beans, and some kind of wheat and corn. He was able to feed his
cattle, and to raise chickens and geese along the banks of this river,
which was only a green ribbon, from six to ten miles wide, four or
five hundred miles long. On this green ribbon a great civilization, so
great and so wonderful that only very learned men can understand how
wonderful and how great it was, grew up.
Find out something about the pyramids. Look up pictures of the ruins
of the Temple of Karnak; and that great stone image, carved out of a
hill, higher than a five-story building, with a head so large that if
a man stood on the top of one ear he could hardly reach the top of the
head with his outstretched hand. The Greeks called this great stone
image, with the body of a lion and the head of a man, a sphinx; but
the Egyptians called it the "Hor-em-khoo," the "Horus-on-the-horizon;"
and Horus was the god-child they most loved, the child of Osiris, the
great sun-divinity, and of Isis, the beautiful mother of heaven. All
this civilization along the Nile would have been impossible had it
not been for the Nile. The great stones that went into the pyramids
were floated down the river. Soldiers and workingmen were transported
on the river. The fields were made fertile by the river, and the
leisure and the wealth that were made possible by the fertile fields
on the river's bank gave men time to think and to feel, to invent the
beautiful picture writings, to cut out the great tomb temples, and to
think the great thoughts of religion, God-thoughts, love-thoughts, and
duty-thoughts.
Now, what happened along the banks of the Nile happened to a certain
degree along the banks of the Euphrates and the Tigris. Mesopotamia
means "the land between the rivers," the mid-river country. Away back
five or six thousand years ago there were people who built great
cities, erected high tower-temples of burned brick. They invented a
curious kind of arrow-headed alphabet (the cuneiform), which they
stamped into clay tablets, brick reading books. On the banks of these
rivers, in that far-off time, astronomers watched the stars, and found
out a good deal about the planets and eclipses. They measured time by
the year of three hundred and sixty-five days, and twelve months, which
means that they had watched the moon and measured the length of the
days.
Then there are other rivers, The Ganges, that runs through the heart of
India, on the banks of which there grew up the great religions and the
curious customs of the Hindus and the Buddhists; and the Jordan, which,
you will remember, flows through our Bible. Around it clusters the
great stories of the prophets, of Jesus and his disciples. When we turn
to Europe, we will find much about the Germans, by finding out all we
can about the Rhine. If you can find out much about the Rhone and the
Seine, you will understand the story of France and the French people.
The Thames is older than London; and along the banks of the Danube
grew up nation after nation. Down that stream have floated war vessels
for different peoples for thousands and thousands of years. Would you
not like to see a collection of boats that would reach from the boats
made of the raw hides of animals by the earlier pagan people along the
Danube, up to the latest and best steamer that now plies up and down
that great river?
None the less interesting are the rivers of the Western continent, the
Hudson, the Mississippi, and the Missouri; the Ohio and the Amazon are
the pathways over which the first explorers traveled. Along their banks
did the first settlers make their homes, and on their bosom did the men
in the wild woods first send their traffics. Who was it that started
the first steamboat up the Hudson? You remember how Abraham Lincoln
when a boy helped build a flat-boat, and how he steered that flat-boat
all the way from Illinois to New Orleans, selling there the truck the
early settlers raised, exchanging it for molasses, and sugar, and the
calico that they needed in Illinois.
When we remember the great service that the rivers have rendered man,
the beautiful stories that cluster around them, the beautiful life that
has sported in their waters, floated upon their surface, and gathered
on their banks, is it not a pity that they are being so despoiled by
thoughtless and reckless men, who wantonly cut down the forests, waste
the trees that grow upon their banks? And then, in our cities, instead
of beautifying the banks and profiting by the scenery, foolish men turn
the back doors of their houses upon the rivers, build barns upon their
banks, make of them the dumping-places into which they throw their
rubbish, street sweepings, and old tin cans, everything that will soil
the water and spoil the scenery.
Do you not think that some day we will again come back to the old love
of the river, even if we do not need it so much as a highway now? for
railroads go faster. We will keep them clean and beautiful, for the
pleasure and the health they yield. You have heard of what a dirty
thing the Chicago river is, how unpleasant it is both to the sense
of sight and to the sense of smell. It is very much the same with
many of the other rivers that flow through our great cities, and even
smaller towns. Some day the children of our public schools, who are
now studying these things, will grow up, and they will find out how to
purify our streams. They will restore their beauty. They will love the
fish in the water so much that they will prefer seeing them alive to
eating them when dead. They will give back the rivers to the birds,
that will sing unmolested upon their banks, and raise their little ones
undisturbed in their nests, built low among the sedges, or swinging
loftily in the poplar boughs above.
So you see, my children, to know the river is to know much of the
geology of the world, much of the plant and animal life of the world,
very much of the history of man, and very much of the higher hopes and
aspirations, the poetry, the morality, and the religion of the human
soul. The rivers were here before man was. They invited man. They
nursed him. They fed him. They marked the places for his settlements.
They helped the organization of the state.
By the way, as a closing lesson, suppose you find out how many of the
states of our Union were named after rivers, and see how many of the
river names you can discover the meaning of; for the rivers were on the
earth before they were named. The names are of men, and some of them
are very suggestive. The rivers are of God. They belong to nature, and
they show forth the laws of nature, which are always the laws of God.
[Illustration: Page decoration]
INSECTS
SOME WATER INSECTS.
CHARLES C. ADAMS.
In field and forest bright-colored and active insects attract our
attention. Aquatic insects, on the other hand, do not, as a rule,
possess such bright colors as their land relatives nor move about
with as great rapidity, yet it does not follow that they are less
interesting.
As would be expected, some of the most interesting things about these
animals are connected with modifications of their form which have
resulted from their aquatic life. It is believed that the ancestors of
water insects have been land insects which invaded the water and have
thus become greatly modified in their new surroundings. Locomotion and
breathing, either one or both of these functions, are, as a rule, very
different in land and water insects.
The variety of aquatic insects, if we consider only the adults, is not
great when compared with the land insects. But when we compare fresh
and salt water forms it is surprising how few kinds there are which
live in the sea, in spite of its vast area and great food supply. So
few are the insects found in the sea, or other salt waters, that, to
most of us, to speak of aquatic insects only calls to mind fresh water
forms. We shall, therefore, refer almost wholly to fresh water forms.
Let us consider briefly a few examples of these.
We may distinguish two general groups, according to their special
habitat. Belonging to the first group are those insects which frequent,
primarily, the surface of the water. These forms which breathe air
directly, and not air dissolved in water, as is the case with many
other water insects, must be kept dry and be able to maintain their
position on the surface of the water. Surface insects, such as the
Water-Skaters, found on quiet ponds and streams, and their marine
relatives, _Holobates_, accomplish this by means of fine hairs which
cover the feet where they touch the water. The same physical principal
is involved here, as when a needle or wire is floated upon water,--that
of surface tension.
The fine hairs on the body of a water insect act in the same way as
those on the feet, and thus keep the insect dry when below the surface.
These insects are thus able to breathe as land insects, on account of
their being on the surface, and consequently their respiratory systems
are not as greatly modified as in many of the insects living beneath
the surface. It must be borne in mind that an insect breathes by means
of the air which enters the body by small openings and is led by means
of tubes, which become very finely divided, like veins, to all parts of
the body. By means of contractions and expansions of the body of the
insect, the air within these tubes is caused to circulate, and thus
impure air is driven out and a fresh supply is pumped in.
Two of the commonest of these surface dwellers, so well known to the
small boy who frequents ponds and streams, are the Whirligig-beetles or
Lucky-bugs, and the long-legged Water-striders or Water-skaters.
The Whirligig-beetles are easy to recognize on account of their
characteristic circular gyrations when disturbed, and by their habit of
associating in large numbers in quiet places. When one of these, groups
is disturbed they exhibit such activity that they well deserve their
name, "Crazy-bugs." The eyes of these beetles are very peculiar in
that each eye is divided into an upper and lower part. Thus the insect
has practically an upper and lower pair, one adapted for sight at the
surface, and the other for vision under water.
The Whirligigs do not seem to be very particular about their food, as
they will accept both live and dead insects which fall into the water,
and even under some circumstances will feed upon plants. When a beetle
plunges beneath the surface, as he often does when frightened, he
carries down a small bubble of air between the ends of his horny wings
and the tip of his body. On account of his body being lighter than
water it takes some effort to dive, but none to rise to the surface.
The two hind pairs of legs which are used so much in swimming are very
much flattened and plate like, making excellent paddles, as is shown by
their exceedingly rapid movements.
The Water-skaters, or Striders, prefer quiet waters, as do the
Whirligigs, but do not have the decided social disposition, shown in
the latter to such a marked degree. These Skaters, on account of their
long legs and short bodies, are the "Daddy long-legs" of the water.
These characteristics and their habitat make them easy to recognize.
They are nervous, active insects in their movements, jumping and
skimming about on the surface with but little show of grace and ease
as compared with the ordinary graceful curves of the whirligigs. Their
food habits are very similar to those of other surface insects, that
is, dead and dying insects found floating on the water. But their
method of taking food is quite different from that of the Whirligigs,
because of the great difference in the structure of their mouth parts.
The Whirligig, being a beetle, has the typical biting mouth parts,
while the Strider has a slender beak or proboscis, by means of which
it sucks the juices from its prey, as do other bugs. The fore legs
are used to seize the prey and bring it within reach of the beak. The
middle and hind pair are used for rowing over the surface, the latter
pair, primarily, for steerage, the fine hairs on the legs making it
possible, as mentioned before, to make use of the surface tension.
Large dimples are formed on the surface of the water where the feet
touch it. One would hardly expect it possible for an insect standing on
the surface of water to get its feet dirty, yet the great care which
they give to cleaning their feet clearly shows that dirt is of common
occurrence, even there. The white or gray color on the lower side of
the body is due to the reflection of light from minute hairs which
cover the surface, and keep the insect dry even when submerged.
The marine relatives of our Striders have some curious habits. Some
of them live out at sea, hundreds of miles from land, where they are
thought to feed upon the dead bodies of small animals. When the surface
of the sea is calm they glide in colonies quickly over the surface,
showing great skill in diving, but if the sea begins to become agitated
they immediately disappear from the surface.
Perhaps the most remarkable habit which a surface insect has is that
possessed by some of the allies of the Skaters, which not only swim in
the water, but actually run on the _under_ side of the surface film. It
would be very interesting to know how such a habit was acquired.
Another interesting group of insects are those which breathe air, as
the surface film insects, yet seek their food below the surface. These
insects are compelled, on account of their air-breathing habits, to
repeatedly visit the surface or communicate in some way with a fresh
supply of air.
[Illustration: INSECTS.
Life-size.
FROM COL. CHI. ACAD. SCIENCES.
COPYRIGHT 1900, BY
A. W. MUMFORD, CHICAGO.
Archimerus calcarator
Oncopeltus fasciatus
Ranatra fusca
Galgulus oculatus
Nezara hilaris
Leptoglossus phyllopus
Benacus griseus
Zelus bilobus
Metapodeus femoratus
Conorhinus sanguisugus
Cicada septemdecim
Platycotis sagittata.]
We have two families of the large-sized water beetles, common in our
ponds and streams. The Predaceous water-beetles and the Water-scavenger
beetles. These are easily recognized, because in the former, the
antennæ are thread-like and not enlarged at the tip. While the members
of the Water-scavenger family have the antennæ enlarged or club-shaped
at the tip. The Predaceous water-beetles are often quite common under
electric lights, where they have been attracted by the intense light.
Their large size and clumsy movements, when out of water, attract
attention. But when seen in water their skill as swimmers is in
striking contrast to their awkward movements made on land. The hind
legs are flattened and very powerful, the surface being increased by
a fringe of strong hairs on the inner side. In swimming the stroke
is made by both legs at once. Perhaps the most interesting facts about
these beetles are those associated with their method of breathing.
The horny wing cases covering the abdomen are very thick and fit
close against the abdomen, except at the extreme posterior end of the
body. The space between the wing cases and the upper surface of the
abdomen forms a large air space. The spiracles, or openings into the
respiratory system, are situated at the margins of the upper side of
the abdomen. When the beetle comes to the surface for a fresh supply
of air it exposes the tip of the body and then by a depression of
the tip of the abdomen allows a fresh supply of air to enter into
the cavity below the wing covers; this cavity is then closed and the
beetle is ready for another trip under the water. When resting in the
water they float with their head downward and the end of the abdomen
slightly projecting from the water; thus a fresh supply of air is easy
to secure. In their food habits these beetles are predaceous, and in
addition to other insects, will even kill small fish.
The Water-scavenger beetles are not such perfect swimmers as the
Predaceous ones. When the latter makes a stroke in swimming it strikes
with both hind legs, while the Scavengers strike alternatingly with
the hind legs. Their method of securing and carrying air, as with
other water-beetles, is remarkable. In addition to the air reservoir
under the wings, they have on the under side of the body large hairy
areas which communicate with the one under the wings. All the air
spaces are thus in direct communication. The respiratory openings in
the Predaceous water-beetles open on the upper side of the abdomen,
but in these beetles they are on the lower side and surrounded by
short hairs which preserve the air film on the lower surface. When the
fresh air supply has been exhausted the beetle comes to the surface,
tips the body slightly, so as to bring the region on one side of the
body just behind the head, to the surface. The long antenna which is
folded backward and reaches to the rear part of the head, occupies
an air space in its apical half, and in addition is covered by fine
hairs, thus being doubly protected from being wetted. At the moment the
beetle reaches the surface, by a stroke of the antenna (on the side
which is nearest the surface, the body being tilted), the film from
the air space in which the antenna rests is carried upward and outward
to the surface of the water, thus forming an opening to the exterior.
By movements of the wings, aided by bellows-like contractions and
expansions of the body, a fresh supply of air is pumped into the air
reservoir.
In speaking of peculiar water insects one must not forget to mention
the larva of _Donacia_. The adult female of this interesting
leaf-eating beetle often cuts circular holes in the large leaves of
water-lilies, and then deposits her eggs at the margin of these holes
on the under side. When the larvæ hatch they make their way to the
roots, upon which they feed. The really remarkable thing about this
larva is how it gets its air supply, as it does not have gills, nor
is it known to visit the surface for a fresh supply of air, and yet
it has a normal air-breathing system. On the dorsal surface, near the
tail end of the body, are two slender, curved, spine-like processes.
The air tubes of the body arise from the base of these spines, and
spiracular-like openings are found at their base.
Two different views have been advocated to explain how it is possible
for the larva to secure air. There seems to be no difference of opinion
with regard to the source of the air supply, from the air cells in the
root of the plant upon which the larva feeds. One view is that these
air spaces in the plant are punctured by the spines and thus the air
is taken directly into the air tubes. The other view is that the larva
bites a hole into the air space and then, by the aid of the spines,
holds the openings at the base of the spine against the air space and
thus the air is taken up.
The Back-swimmers are curious little fellows which swim upside down in
the water, and by means of their sucking mouth parts, prey upon other
small animals. The lightness of their bodies and the large amount of
air which they carry with them make it necessary when they wish to
remain below the surface to hold fast to some object. Thus it takes
constant effort in order to remain below the surface. For this reason
it is quite natural that they should very often be found floating at
the surface where no effort is needed to maintain their position and
where an abundant supply of air is accessible.
Another method of securing fresh air, but differing from that of any of
the insects previously mentioned, is by means of elongated breathing
tubes, thus allowing the insect to remain submerged and yet secure
a fresh supply of air from the surface. This method is used by some
predaceous water bugs, as shown in the plate, _Ranatra fusca_. As with
all of our Predaceous water bugs, which have the elongated respiratory
tube at the end of the body, the Water-scorpion has its fore legs
adapted for capturing and holding its prey, which consists generally
of small fish and insects. The apical part of the fore leg folds back
on the basal part which is grooved on its inner face, as a knife blade
folds into its handle. As the slender legs of this bug would indicate,
it is not an active swimmer, but crawls about slowly.
Doubtless the best known, to most people, of this type of breather,
are the Giant water bugs, which accumulate in such large numbers
under and in the globes of electric lights. The paired nature of the
breathing tube is well shown in the plate. These bugs are powerful
swimmers, as is shown by their flattened hind legs. Even young fish
are not overlooked by these voracious bugs. A South American kind is
much larger than our species, reaching from four to four and one-half
inches in length, or about twice the size of our species. The shortness
of the air tube suggests that this organ is not used in just the same
manner as in the Water-scorpions, and the areas of fine hairs on the
under side of the body suggest that these insects may be somewhat of a
compromise between those insects which carry air below with them and
those which remain submerged, except for the tube which communicates
with the air.
Most of the insects previously mentioned are ones which throughout life
live in water, but a very large number are aquatic only during their
larval or immature stages. The Mosquito is a good illustration, of
this type. In some of its habits the Mosquito is well known, but this
is primarily due to the biting habit of the female. The researches of
recent years clearly show that the annoyance from the bite itself,
is, in the case of some kinds of Mosquitoes, only a small part of the
mischief that they can do. The life history of the Mosquito has been
summarized somewhat as follows by Dr. L. O. Howard: The eggs are laid
at night, in a boat-shaped mass containing from two hundred to four
hundred eggs. These may hatch in 16 hours, the larval stage lasting
about a week, and the pupal stage about 24 hours. Thus the entire cycle
may be completed in 10 days, under favorable circumstances, but may
be greatly delayed by a low temperature. The rapidity with which the
complete cycle may be passed through makes it possible for a very large
number of broods to occur during a single season.