THE SPEECH OF ANIMALS
AGROUP of American biologists, not without help from the microphone, have been busy eaves- dropping, and begin to think that they have intercepted and interpreted the conversations of the so-called lower animals---of insects, mammals and birds. The philoso- phers, too, have been generalizing on the results, with an unexpected unanimity of conclusion that most animals, -even cold-blooded fish, communicate by sound. Do they ?
The race of man is, of course, very deaf. Darwin told us that few men after passing thirty years of age can so much as hear the bat, though even the smallest of the tribe, the little common pipistrelle that now begins to hawk about our lawns, shrieks like an owl. The air echoes and shakes with much more rapid vibrations than this mouse-like squeak. The feet of insects clatter on the ground ; a million wings swish and sough like the wind ; the shrews shrill their hunting notes, and under the waters (it is maintained) the fish bark and yelp to call stragglers to the pack.
A good deal of information, not quite deep enough for definite conclusions, has been accumulating about the senses of insects, which are the least articulate of animals. We now know exactly how, though not why, their notes are made by the few insects whose cries we arc not too hard of hearing to detect. The wing noises are not produced by what. Virgil called " the oaragc of the wings "--Remigium Alarum striking the air, but rather by the friction at the rowlock. The square base of the wing scrapes against the hard material in which it is set. When we put an ear to the bee-hive in winter and delight to note that high, clear, vibrant hum, proving how lively is the spirit of the hive, the wings produce it by the same -sort of method as the cricket or cicale whose " song " was taken by the Greeks, after a pretty legend, as the symbol of music. It is frictional. Perhaps no other articulate sound, if the phrase is allowable, fills one with quite such wonder as the cry of Queen bees before swarming time.- It is delivered by a vibration of parts of the wing invisible to the eye ; and is one of the rather few trumpet notes that obviously affects a mass of others. Some drill-master ants hiss their slaves into harder work ; but such vocal commands are very rare. The high, angry note of a charging wasp or bee—not very different from her cry when captured—is probably due merely to the extra speed of the wing movement ; and therefore is inci- dental, not, as it suggests, venomously intentional ; but we must believe that the many ingenious devices by which insects " utter " their scraping noises—some by wings, aided by an expelled draught front special tubes, some by the sawing of a limb in a peculiarly adapted nick, sonic by the rubbing of one piece of armour against another—have an aim or purpose, and that the purpose lies in the ear of another or of the many other insects that attend to it. The beetles---an innumerable crowd--are often drummers as well as fiddlers. They will tap their heads violently and frequently against wood or other hard substance, almost like a woodpecker, and so beat a tattoo that may be loud enough to be oppressive. It is very much louder, for example, for the size of the animal than the warning beat of a rabbit's foot, which is one of the very few noises made by mammals which one may claim definitely as a signal. The beetles—including the death- beetle—seem to tap, as birds sing, chiefly and above all because they enjoy practising a self-satisfying accomplish- ment. However the gift emerged, it is now indulged because it gives pleasure to the performer. Birds have developed a language far beyond the reach of any mammal or insect, though that language is not the song that delights our ear, but rather the lesser calls, murmurs and alarm notes, in which to some extent the female shares.
In most animals there is one master sense much greater --so far as they can be compared—and finer than any other ; and when we can discover this we may perhaps assume with safety that the other senses are unremark- able. Is there any single animal in which this master sense is hearing ? In most insects it is certainly the sense of smell. The quite incredible distance at which a male Emperor moth will discover a female has astounded every naturalist. The writer has never known the lure of a caged female to fail ; and it is believed that the scent carries miles. The sense is accurately " directional " in bees, wasps, butterflies, moths and beetles. Some will even crawl through a keyhole into a shut room where the scent originates. A dog's sense of smell excels man's by many hundredfold. The moth's may be as far in front of the dog's. In birds the supreme sense is sight—certainly in the eagles, which see rather than smell their prey from afar, and hawks and pigeons. Among the best listeners may be reckoned horses, red deer and owls ; but there is no evidence that their acuteness of hearing is at all comparable in quality with the sense of smell in dogs or moths.
The live world on the whole is hard of hearing ; yet if there is a fifth, sixth (or, should we say, an eighth ?) sense it may be more closely connected with hearing than with sight or sound. Many people in the War—especially women—were aware of shell-firing at vast distances, but were often unsure whether they heard or felt the vibration. Insects, which have no central nervous system, and often possess rather inferior organs of sense—especially of ear—take up sensation by the little " ganglionic centres," or local brains, scattered all about their bodies. These nerve-centres may very well be sensitive to the vibrations of the atmospheric air which we call sound. They may hear, that is, without ears, as without consciousness. This may be so ; but it is more probable that " the receiver " in their bodies responds not to sound waves which belong to the atmosphere, but to electric waves over the ether ; and if this proves to be the fact, a sense not known to us, though doubtless possessed by us in some measure, is part of the equipment of the insect. When the Queen bee holds her wings over her back and the high clear note, issuing from her wing sockets, brings the workers to their knees, the sound, as we hear it, may be a mere accident of the vibrant message, just as wireless messages are not sound, but are translated back into sound because of our poor inability to receive them directly.
It is no explanation of the wonders of instinctive action or knowledge—a human intuition, a horse's terror of earthquake, a rat's desertion of a falling house, an eel's cross-country journey, a bird's bee-line migration, a moth's response to the distant summons of its mate, a dog's homing sense--it is no explanation of these to attribute to the animals, as some have, an " electric sense.". As Occam, the old schoolman, advised, we must not multiply causes beyond necessity. Nevertheless, recent investigations at least suggest the possibility that instinct may be prompted by ethereal vibrations which are not comprehended in the senses of sight, hearing, smell or feeling, as we understand them :- " Star to star vibrates light. May soul to soul Strike through some final element of its own Y " But that again touches a wider question.
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