Part 10

We really know far less about hearing than about sight. The eye is where we can get at it, to look inside, and to see how it works. But the ear, the inner ear that is, where the hearing is done, is set deep inside the head, in the midst of a solid bone, the hardest piece of bone in the whole body except the teeth. Nobody, therefore, really understands how we hear.

We do know, however, that the ear is two different things. One part of it is the organ of hearing—I am speaking always of the inner ear—while another part, as I have already explained, is the organ of the sense of equilibrium, the feeling of direction and right-side-up-ness. But just how much of the ear goes for hearing, and how much for right-side-up-ness, and exactly how either part works, and especially just how we tell one sound from another, are things that are still left for somebody to find out.

Nor do we know much more about smell. We know that the smelling is done in the upper part of the nose, that the nerves of smell do not cross over and report to opposite sides of the brain, as so many other nerves do. But how we tell one odor from another, nobody understands; and we are even farther away from understanding than we are in the case of the eye.

We do, however, understand taste. At least we understand as much about it as we do about sight; for the two senses are much alike. There are four kinds of taste spots, scattered over the tongue and the inside of the mouth, mostly on the tongue. Each of these gets one kind of taste—salt, bitter, sour, or sweet. Oddly enough, different people have these four sorts bunched in different parts of the tongue, so that not all people taste the same thing in quite the same place.

But you will say at once, we taste many things that are neither sweet, sour, salt, nor bitter; there must be many more than four tastes. There are not. What we commonly call tastes are really smells. We smell things that are in the mouth, and think we taste them.

If you don’t believe this, simply hold your nose. It is an old trick to get somebody to close his nose tightly, and then while all sense of smell is thus cut off, to bring into the room a piece of raw onion, put it in the victim’s mouth, and ask him to guess what it is. If the onion is not brought into the room until after his nose is shut off, he cannot tell what it is that he is eating. For the onion has almost no taste. But the moment one lets go his nose—then he knows! There is no doubt that the onion has smell—enough and to spare!

Almost any of the senses can be fooled. Put your finger on you forehead; then move your head slowly from side to side so that the finger, held motionless, slides over the skin. Your muscular sense and your sense of equilibrium both testify that the head is moving and the finger is still. Yet you can’t make yourself believe it. It insists on feeling as if the head were still, and the finger moving.

Or try the senses of heat and cold. Take three dishes, one of hot water, one of cold, and one of a mixture of the two that shall feel neither warm nor cold but tepid. Put the fingers of one hand in the hot water, and the fingers of the other hand in the cold water. Keep them there a minute; then put them both in the tepid water. The tepid water will feel hot to one hand and cold to the other. Really it isn’t either. Perhaps, too, you have noticed, when you go in bathing, that as you wade in, you feel the cold only at the surface of the water where the skin was last wet. Hence the wisdom of going in all over at once with a header.

Even the sense of touch, in general the most reliable of the senses, can be deceived. When you are fishing and get a bite, where do you feel it? Most fisherman feel the bite at the end of the line, as if their nerves actually ran the length of the rod and down the string to the hook! And when a ball player cracks out a long hit, I leave it to all boys, if he doesn’t feel the place in the bat where it hits the ball. Or to take a commoner example, when you touch your hair, where do you feel the touch? In the hair itself where there is no feeling at all, or in the scalp where it really is? Or once more, if you hold the point of your nose between two fingers you feel one nose; but if you cross the fingers, and then touch your nose between the crossed parts, then you feel two noses.

Still on the whole, our senses are pretty reliable. The eleven different sorts of feeling spots in eye, tongue, and skin, that tell us about red, green, blue, heat, pressure, cold, pain, sweet, sour, bitter, or salt, and the ears and nose which we don’t know so much about, all these tell us, on the whole, the truth. Yet we never can be quite sure; so that wise people, and especially wise boys and girls, will beware of contradicting other people who chance to see, hear, taste, smell, feel or believe, a little differently from themselves.

XXIX

The Sight and Hearing Of Ants

So much then for our own senses, our sight, hearing, taste, pain, and the rest of the ten, or as many more as one thinks it worth while to count. The animals also have their senses, never apparently, more than ours, oftentimes fewer, sometimes very few indeed. So far as they have senses, these are like our own. But since some animals haven’t any eyes, yet can see—a little; and some haven’t any noses, yet can smell; and most of them haven’t any skins, yet can feel; one may easily guess that their seeing and smelling and feeling is not done quite in the same way that ours is.

I begin, then, with an animal that has eyes and can see, has no nose and can smell, and does its hearing with its legs. This animal is the ant. Of course, there are a great many different kinds of ants, as there are a great many different kinds of human beings, and these are by no means all alike. Some are black, some white, some yellow. Some are, for size, like the smallest letters on this page; some are more than an inch in length—and you can imagine their bite! Naturally also, sight and hearing, taste and smell, are not quite the same in them all.

Time would fail me to tell one half the strange ways of these interesting creatures, the most interesting creatures, probably, in all the world of little animals. Just as soon as you can, you must get hold of the books of Fabre, M’Cook, Sir John Lubbock, or Professor Wheeler, and read these strange things for yourselves—how the ants live in cities underground, have workmen and soldiers, carry on wars against their neighbors, raid their enemies’ nests and make slaves of the captives, have plant-lice for cows, and milk them of their sweet juice, and in return for this, feed and care for the plant-lice and their young, pasturing them on the roots of plants, and making no end of trouble for the farmers whose plants they are.

All this, I say, and many times more, no less fascinating, you can read for yourselves in the proper books, not only about ants, but about their cousins the wasps and bees as well. Just now, however, we are concerned with how much the ant knows, and how he manages to find it out.

Ants, in general, you must remember, live for the most part in total darkness under ground. The workers, to be sure, leave the nest in search of food, but the industries of the ant city, the storage of food, the care of eggs and young, and the building of the city itself, go on as if at the bottom of a mine. The queen ants, which lay all the eggs for the colony, and the male ants, who like the drone bees are gentlemen of leisure and don’t do much but loaf, are for most of their lives like the vine tendrils which I have already told you about. Whenever the light falls on them, they turn their heads down stream to the ray; and so if they move at all, they have to go toward the dark.

This, of course, holds them prisoners in the nest. But when at certain times of the year, a new brood of males and females appears, these ants, which, unlike the workers, have wings, suddenly become like the leaves and stems of plants; they have to head toward the light, and when they crawl or fly, they have to fly toward it. So when the rays of the sun happen to strike the nest, and light up the interior, out comes the swarm of winged males and females, leaving the wingless workers behind. Away they fly toward the sunlight; and those who are fortunate enough to find a suitable spot unhook their wings, settle down to found a new colony and a new nest. Thereupon, for the remainder of their lives, they turn their backs on the light like a tree root. The rest, however, die, after they have lost their wings, so that one sometimes finds great quantities of these scattered about after the swarming.

The workers, on the other hand, who have to be in and out of the nest about their business, do not have this tropism. They can take the light sidewise, or end on, or any other way, just as we can. The object of the tropism is to keep the males and females in the nest until swarming time, and then to get them out. Really, could there be invented a simpler or more effective way?

The worker ants can see. What is more, they can see colors. Nevertheless, they do not usually see quite the same colors that we see. For the most part they are red-blind, just as one man in thirty is. But unlike the color-blind human being, many ants make up for this red-blindness by seeing one or two other colors to which we are blind.

Of course, you know the colors of the rainbow, beginning with red at the bottom and running up thru orange, yellow, and green to blue at the end. You see the same colors also in a dew drop, or in the light which has come thru the corner of a square ink-well or the beveled corner of a mirror. These are the so-called primary colors, by mixing which all other colors can be made.

Now we, ourselves, do not all see the same rainbow colors. The great Sir Isaac Newton, who made a special study of rainbow colors and gave them their names, claimed to see seven—red, orange, yellow, green, blue, indigo, and violet. I myself can see only six; that is to say, I see only two colors beyond the green. More persons, apparently, see six than seven. Try it for yourselves and see how many you see.

The curious thing about the ants is that certain sorts, at least, 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.

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.