see the rainbow colors as many of us do—green, blue, indigo, violet;
and after that keep on still farther beyond this point, and see one
or two more colors, which we never see, and for which, naturally, we
have no names. Then, as I have said, to make it up, they are totally
blind to red, and nearly blind to yellow. Some ants go even farther
than this. They are totally blind not only to red and yellow, but to
all the colors which we see. They do all their seeing by means of
those two or more colors, farther out in the rainbow than the
violet, to which we human beings are totally blind.
There is a considerable practical convenience in this. The worker
ants, while they themselves run freely in and out of the nest, from
darkness to light, usually try to keep their eggs and young in the
dark. So when you turn over a stone and open into an ants’ nest, the
most that you get is a glimpse of piles of white eggs or larvae, and
a throng of workers skurrying about to drag them out of sight into
the ground. You really can’t see anything at all of the regular
daily life of the underground city.
But people who study ants simply carry them into a dark room, and
look at them by red light. Since the ants cannot see red, they think
they are still in total darkness, and so keep right on undisturbed
with their work as usual.
Doubtless, it has already occurred to you, that in this particular
the ant’s eye is very like a photographic camera. You who have
cameras, open your plates and films by red light, because the
sensitive chemicals are blind to red, and so treat red light as if
it were darkness. You probably do not know, however, that it has now
become the practice to take especially sharp pictures of small
objects thru a microscope by means of some of these colors which the
ants see and we do not. These colors do not come thru glass, and the
instruments have to be made of quartz; but they take beautiful
pictures in what seems to us total darkness, and what to an ant
would seem some familiar color, about which we know nothing.
On the whole, then, certain ants at least rather have the advantage
of us in seeing colors. We, on the other hand, more than make it up
when it comes to hearing sounds.
We ourselves, however, differ in this a good deal from one another.
Practically everybody who can hear at all, can hear all the notes of
a piano, from the big growly end up to the little squeeky end. You
young people can hear much shriller sounds than any on a piano; but
we old codgers, whose ears are getting stiff, do not hear shrill
sounds, even when we hear perfectly well those of lower pitch. The
squeek of a mouse is about the limit for most people. Some can hear
it, some can not. But cats can hear easily a mouse’s squeek, and
much higher sounds besides, such as no human being can hear at all.
But the ants are still more inferior to us than we are to the cats.
Some sorts which have been tested, can hear only two, and sometimes
only one, octave above “middle C” on the piano, tho this is only
half way up to the squeaky end of the key board. They hear well
enough up to that point, and then are deaf to all sounds beyond.
Ants, moreover, do their hearing thru their legs. We ourselves, do
something like this, when we grip one end of a stick in our teeth
and scratch the other end with a pin. Even a lead pencil will do for
the experiment; the sound is twice as loud when we shut our teeth on
the wood and hear the scratching thru the bones of the jaw, as it is
when we listen with our ears alone. Miss Helen Keller, completely
blind and deaf, managed nevertheless to enjoy music by holding a
music box in her hand, and feeling the jar; and she conversed in a
telegraphic alphabet by tapping with her foot on the floor, taking
the reply in the same way, by the jar, when anyone answers her.
The ants manage in much the same way. Stand an ant on cotton wool,
and he is totally deaf to all sound. No sound, high pitched or low,
can reach him thru the air. But put him on a hard surface, on his
legs, and he hears thru his legs, taking the jar much as Miss Keller
does. In fact, all sound is jar, either of air or of something else;
a fact which you can easily prove for yourselves by striking a bell,
and then touching a finger nail to the vibrating edge. Naturally we
hear best with ears; but lacking these, any part of the body will
make shift that can feel jars.
XXX
Ants’ Noses
Ants see, then, and hear. But their hearing is not at all good;
while they do most of their work in pitch darkness underground,
where they can not possibly see anything anyway. So they depend on
touch, and still more on smell. Smell, therefore, is their chief
sense, as sight is ours. So much thinking as they do, they do
largely with their “smell center.”
We in a strange country, find our way back home by remembering what
we saw on the way out. An ant gets home by following the smell of
its outward trail. We recognize our friends by sight, and know them
by the way they look. An ant recognizes its friends by touching them
with its feelers, as no doubt you have often seen ants do, and so
getting the familiar odor, smelling out each other’s claims to
acquaintance.
For the feelers or antennae are the ant’s nose. It feels with them,
and it also smells. As you can discover by looking at any ant, the
antenna is like some whips which have a stiff handle and a long
flexible lash fastened to its end. The handle sticks out sidewise,
and the lash is jointed so that it can be moved about freely.
Our common brown ant has eleven joints in its whip-lash. With the
joint at the tip it smells its nest. With the tenth joint it gets
the general odor of the colony to which it belongs. With the ninth,
it follows the scent of its own track. With the eighth and seventh,
it recognizes the helpless young which are its care. By means of the
sixth and fifth, it knows its enemies, the inhabitants of other ant
cities with which it is at war. What the remaining four joints next
the handle are for, is by no means clear.
An ant, therefore, which has had the outermost joint of its feelers
cut off, or has lost them in battle, does not know its own nest. One
that has lost the two outermost, does not recognize its fellows when
it meets them away from home. One that has lost the outermost three
joints, can not smell its own track and so can no longer find its
way home. If the seventh and eighth joints are gone, the ant no
longer has the slightest interest in the eggs and the helpless
young, which before the mutilation it would have fought to the death
to defend. Apparently, it no longer knows what they are; like the
men who wake up some morning with a little blood clot on the surface
of their brains over their left ears, who can see words but not read
them, and don’t know what their wives and children are. On the other
hand, ants from different nests, which have lost the whole of their
antennae down to the fourth joint, live together in perfect peace
and harmony. But ants from different nests, deprived of their
antennae only as far as the sixth joint, straightway start to
fighting like cats and dogs; and never leave off till they are all
killed or disabled.
Apparently then, the ant has enemy-smelling spots, and egg-smelling
spots, and track-smelling spots, and friend-smelling spots, and
nest-smelling spots, strung along in order on the lash-like part of
its feelers; so that when one of these sets of spots goes, that
particular sort of smell goes with it.
The ant, I say, depends greatly on smell. Probably it never knows
any of its fellows, or any of its young, separately as individuals.
It only knows that they have a certain familiar smell. At any rate,
ants taken from a nest, soaked in water with ants from another nest,
till they have taken on the foreign odor, and then returned to their
own nest, are promptly set upon and killed as if they were invaders.
But ants soaked in water with members of the colony, so that they
have the proper colonial smell, are received as brothers.
Each sort of ant has its own peculiar odor, so different from that
of other sorts that even the blunt human nose can tell them apart.
Each nest of ants, too, has a slightly different smell from that of
other nests of the same sort, so that each ant knows its own, tho
the differences are too small for us to detect. All the ants of a
colony are the children of the single queen, who lays all the eggs
for the entire ant city. All the ants of a hill, therefore, instead
of looking like their mother, smell like her. Each ant, then,
recognizes its own brothers and sisters, its mother, its mother’s
sisters, and the children of its mother’s sisters, who are its
cousins. All these have the familiar smell, and the ant treats them
as friends.
Ants from a related nest whose smell is nearly right, but not quite,
are received with suspicion, and not allowed to take any part in the
care of the young. Those whose odor is still less familiar are
dragged about and roughly handled, but allowed to live. But those
whose odor is entirely strange are promptly lynched, and their
bodies dragged away to the waste heap.
The odor of the queen ant remains the same thruout life.
Consequently, any ant will always recognize its own mother. But the
odor of the worker ants changes with age. An ant, brought up in a
nest, learns the queen odor, and the general nest odor, and the odor
of workers of its own age, and of all younger than itself, and of
all older than itself to which it is accustomed. But a young ant
taken away from its nest, and kept away for two months, will find
that its older sisters have meanwhile taken on a new smell. It
treats them therefore as enemies. Yet an ant, once familiar with the
odor belonging to any age, will remember it for at least two years.
There are some other peculiar results of the ant’s reliance on its
smell. Occasionally, in the fields and woods, one finds what are
called mixed nests of ants. Two different sorts of ants, which
ordinarily are mortal enemies, springing upon one another and
fighting to the death on sight, are found living together in
harmony, caring for each other’s young, and in all respects behaving
as if they were all of the same sort.
The way these arise is this: Two young queens, of different kinds,
starting their new colonies, happen to settle so near together that
the young workers mix with one another as soon as they are hatched
out. From their infancy, therefore, each sort knows the smell of the
other; and being used to it, thinks it quite the right and proper
thing. So the ants grow up together, while the odors change so
slowly with age that they never seem strange. Indeed, such nests
have been made in this way by students of the ways of ants, with as
many as ten different sorts in them, all living peacefully together.
When, however, such a nest is separated, and the two sorts of ants
kept apart for a few months, the mixed nest cannot be reformed. Each
sort of worker ant will recognize and care for the queen of the
other sort, and all young of the other sort of all ages up to the
time when the nest was split up. These the ant remembers. But all
workers older than this have, of course, taken on an unfamiliar
smell. The old friends have become enemies, to be slain on sight. So
each sort of ant befriends the young of the other, whose smell it
recalls, tho it has never known the individuals; while it fights to
the death its former friends of its own age, with whom it has been
working side by side, but whose odor has become strange.
Evidently then, an ant has no instinctive liking for any particular
smell. It simply has to learn a set of smells, and what they mean,
just as we have to learn our lessons. I think you will agree that
for ants living under ground, smell is on the whole the best sense
to tie to and do one’s thinking with. But for us, living upstairs in
the sunlight, sight is, I am sure, very much the most useful of all
the senses.
XXXI
Some Other Eyes and Ears
The rest of the insects are, in general, much like the ants. They
have their feelers or antennae, growing out in front of the head,
with which they both feel and smell. Most of them seem to taste
their food in their mouths. Nearly all have eyes.
As for ears, a good many insects, apparently, hear as the ants do,
without any regular ears, and just by feeling the shake of what they
happen to stand on. At least, nothing is known about their having
any regular ears; though it is quite possible that some of them hear
through their wings. Certainly, a tight hard wing, like a house
fly’s, when one wasn’t using it for flying, ought to make a very
decent sort of ear, one would think.
Grasshoppers and the like have proper ears. Though instead of being
where we have ours, on the sides of our heads, Grasshopper Gray
carries his ears on his hind legs, on the side of his great jumping
thighs; while the ear itself, instead of looking like a human ear,
is like a tiny drum—a tight thin head with a hollow underneath. Some
other insects have their ears on the side of their bodies, about the
middle. You can see these things for yourselves; they are not hard
to find.
[Illustration: Ear of a mole cricket on the front leg.]
Some of the jelly-fishes have ears, not at all good ones, but still
ears. Some also have eyes, not so good even as the ears, and not
good for much anyway. But the same kind of jelly-fish doesn’t have
both ears and eyes; whichever he gets, he goes without the other,
having apparently not sense enough to manage both. As for the
sea-cucumbers, they sometimes have more than fifty ears apiece, none
of them good for much.
Most all of these simpler sorts of ear are much like tiny rattles.
There is a hollow ball lined with nerves. Inside the ball is a small
hard ear-stone, or a number of smaller grains of ear-sand. When a
sound comes along, (for a sound is nothing but jar), it shakes the
rattle, so that the little stone inside bangs against the nerves.
Then the animal hears. In the cod fish these ear-stones are
unusually large, as large as the end of one’s thumb; children
sometimes call them lucky-bones, and use them for playings. We also
have these little rattles, two in each ear, with ear-sand. But
these, which are all there is to the ears of lowly creatures, are
only a small part of our hearing machinery.
[Illustration: Back of the frog’s eyes are the ear drums.]
You will find the ears of lobsters and crayfish, which are little
fresh water lobsters, just at the point where the smaller feelers,
which are double at the end, join the body. These, too, are merely
ordinary ear-rattles; you can make out the opening on the upper side
of the feeler. Of course, you know the ears of the frog—the big
spots on the side of the head, back of the eyes. These spots are the
drums of the ears; the real ear, much like our own, is inside. We
have such a drum, only it is at the inner end of the hole into the
ear, where it is much safer than it would be outside.
[Illustration: A newt.]
The fish’s ear you cannot find. That is inside; and the fish hears
through the bones of his head, just as we do when we hold a stick in
our teeth and tap the end, while we keep our ears stopped with our
fingers. But the long dark stripe which you see on many sorts of
fish, running from the place where the neck would be if fishes had
one, the whole length of the body to the tail, and also forward
across the head and around the eye, only you can’t make it out so
well there, this also is a sort of ear. In fact, the ear itself is
really a part of this “lateral line” very much improved—so much
improved that we human beings and the four-footed beasts and the
birds haven’t found it worth while to keep the lateral line at all.
But the newts and salamanders still have it.
As for eyes, of these also there are all sorts. The star-fish has
five, one at the end of each of its five arms, a tiny black dot. The
jelly-fishes, some of the commoner sorts at least, have their eyes,
such as they are, where the long tentacles join the center of the
bell underneath. Some of the worms have several hundred eyes; some
have a pair of eyes on each of the dozen or twenty joints of the
body. The leeches, the common blood-suckers which get on our legs
when we go swimming, have ten pairs of eyes, all on the front end.
Oysters, clams, and other “bivalves” have their eyes along the edge
of the shell. Many of the snails have them on stalks, which they can
pull back into the head or push out. The snail in Mother Goose, that
“...put out her horns
Like a little Kylo cow”
and frightened the four-and-twenty tailors, was really only putting
out her eyes to see these valiant heroes. Some of the shell-less
snails, or slugs, besides the eyes on the ends of their horns, have
a lot more, occasionally nearly a hundred, sprinkled over the back.
Such eyes, however, are really not good for much. They serve to tell
light from darkness. They let the creature know when a shadow falls
on him—which is usually the shadow of something on the point of
eating him up, so he gets warning and bolts. We ourselves can do as
much with our eyes shut tight; and that’s about all most eyes will
do wide open. There are not many really good eyes, till you get the
single pair of the animals with back bones.
[Illustration: The Star-fish Has Eyes on His Arms; The Slug Also Has
Eyes on His Horns; The Snail Has Eyes on His Two Longer Horns]
Still there is one very fair sort of eye, though not nearly so good
as ours, and that is the strange compound eye of the insects.
In general, the insects have either one, two, or three little eyes,
at the front of their heads, which they use, probably, for seeing
things close to them. Besides these, they have their two great
compound eyes, often many times larger than all the rest of the
head. The two together usually make almost a ball, and with them the
bee or wasp or moth or dragon-fly sees clear round the horizon,
above him and below him, all at once, and all equally well.
You know if you take a roll of paper, and look through it as if it
were a telescope, you see a small bright spot at the end. If you had
two such rolls, and could look through them both at once, you would
see two such spots. If you had a thousand or more such paper tubes,
and could look through all these at once, you would have something
very like the compound eye of an insect.
Our eyes, as you know, are cameras. They form real pictures at the
back, on the retina. But these compound eyes are not cameras, and
they do not form any pictures anywhere. Instead, the insect looks
out through one eye tube, and sees one spot of color; and through
another, and sees another spot; and through a third, and sees
another. Looking through some hundreds all at once, he sees a
corresponding number of hundreds of spots.
But even ten thousand such spots would make no such sharp picture as
we see in the small center of our field of vision where we see most
clearly. Flies and ants and bugs and grasshoppers see only as we see
things far round at the sides of our heads. They can see much
farther round than we can; but they can’t see nearly so well
anywhere.
So a fly never could see to read, even if he could ever learn. The
page of letters and the white paper would simply mix to a gray blur.
A fly cannot get through a netting with a half inch mesh, unless
there is a light behind it. Altho the holes are many times larger
than his body, he cannot tell hole from string well enough to fly
through. If you try to put your whole hand on a fly, or hit him with
one finger, you cannot do it. He sees something dark coming, and
stands from under. But you can often get him by bringing down the
whole hand slowly; and then, just as he is about to take flight,
dropping one finger on his back. He can see the whole hand against
the wall of the room; but he cannot see clearly one finger against
the others.
So on the whole, the fly does not really see much with his little
eye; in fact, taking, one thing with another, we boys and girls and
men and women probably see more distinctly, and make more use of our
eyesight, than any other creature that breathes.
XXXII
Having Senses and Using Them
All animals feel. So, too, do all plants. At least, all animals and
plants sometimes move when they are touched. So they must feel.
Whether they know that they feel or not, is another matter. Most
likely, all plants and all the lowest animals, feel as we feel in
our sleep, when we get tired of one position and turn over, or feel
cold and pull up the bed clothes, without knowing at all what we are
about. Somebody has said that the mind “sleeps in plants, dreams in
animals, and wakes in man,” and that is really just about the state
of affairs.
All animals except the very lowest also taste and smell. At least
they choose their food, as they couldn’t very well do if they did
not smell or taste it. Tho when you come to think of it, for an
animal living in the water, taste and smell are all the same thing.
The food is in the water, the creature’s mouth is full of water, and
its nose (if it happens to have one, as most water creatures do not)
is full of water also. So it doesn’t make much difference whether
you say that the creature tastes the water or smells it.
Most animals have eyes and can see. Not a few also, which have not
eyes, can still tell light from darkness. The earthworm, for
example, has no eyes at all, yet it always avoids bright light, and
keeps in its burrow when the sun is out. Neither has it ears, yet
when it is part way out of its hole, it will at once pull back again
when certain notes are sounded near it on a piano.
We might almost say that every bit of the life-jelly of which all
living things are made has itself all the five senses. All of it
seems to feel, and all in some faint way to see and hear, taste and
smell, move and remember. Besides this, the life-jelly makes itself
all sorts of eyes and ears, all sorts of mouths and noses, all sorts
of muscles and brains, in order that it may see and hear, smell and
taste, feel and move and remember better than it could do without
them.
But all this time that we have been thinking about ants, and
star-fish, and earthworms, we have been neglecting the creatures
which we really care most about, and certainly know best, the cats
and dogs and horses and rabbits and various pets of all sorts which
we know by name, and which in return we believe are fond of us.
These animals, the four-footed creatures with fur, and the birds,
are of all living things most like ourselves. They are most like us
in body, they are like us also in mind; and they have the same
senses that we have—five, seven, ten, a dozen or more, according as
we choose to count them.
They have, I say, the same senses that we have; but they use them
differently. Nothing, I think, is more striking about dogs, for
example, than the small use they make of their eyes. Often, indeed,
they seem half blind; they fail to recognize their own masters ten
yards away; get separated from them, and run round frantically,
smelling of everything in range; while all the while, the master can
see the dog perfectly well, and pick him out at a glance from a
dozen others. One would think that the dog would simply look round,
see his master, and join him.
I don’t think that they really are half blind. They probably can see
nearly as well as we. They simply don’t use their eyes, and depend
instead on their noses. Sight is the most important sense for us, as
it seems to be for the birds. But the beasts seem to depend most on
smell.
The tales we read about the scent of dogs, and especially of
bloodhounds, are often almost beyond belief. The bloodhounds, I
understand, are so-called, not because they are especially fierce,
in fact they seem to be on the whole a rather gentle sort of dog, as
dogs go, but because they are supposed to smell one’s blood, and to
be able to follow the smell almost anywhere. I suppose they really
do smell the perspiration; but they do it thru the sole of a heavy
boot, when one has simply walked along over the ground; and they
follow that inconceivably faint odor, hours after, and pick it out
from all other smells, even those of other people cutting across the
track.
Yet I sometimes think we make out the dog’s sense of smell to be
more wonderful than it is. The same dog that tracks footprints so
marvelously will nose round in all sorts of dirt as if he had no
sense of smell at all, and eat things that we would not have in the
house.
We also can do a little smelling. Anybody can smell the vapor of
bromin in the air when there is one part in two hundred thousand.
Hydrogen sulphid, which is the gas that makes the smell of rotten
eggs, will scent up 1,700,000 times its bulk of air. The least
little grain of musk will scent a room; as little as the fifty
thousand millionth of an ounce can be smelled by a good nose. Tea
and wine tasters (who of course are really tea and wine smellers)
can pick out the place where grapes or leaves grew, and the season
of the year. Wine tasters can tell one year’s vintage from another,
and distinguish between the top and the bottom of a single bottle.