Popular Science Monthly/Volume 39/September 1891/Musical Insects
IF we would hear the children of the sun, we must shut the door of our prosaic room behind us, and hurry out before the coming on of dusk to the pond, into the green field, on the moor, to the edge of the wood where life in the double form of animal and plant unfolds itself without restraint. From up in the air, from plants, flowers, grass, holes in the ground, and the moisture of puddles, come a chirping and rattling, a humming and buzzing, a piping and singing of the host of winged and wingless creeping and hopping insects. Let us guard our steps. Near us a musk-beetle is groping with his long, knotty feelers along the bark of a willow tree. The shrill tone of his chirp strikes upon the ear; and if we are gifted with musical sense enough we may succeed in hitting the key-note of his register. We need only use our chamber-tone, the treble A, or any other note easy to whistle, in order to determine from it the pitch of the beetle's song. We shall find then that he has the highest-pitched voice in all Nature's concert—the third octave of D. From the distance comes a humming which is related to that chirping as the alto to the treble. It is the sound of the vibrating wing of the moss-bee. The buzzing bass of the bees and wasps is about an octave lower than our chamber-tone A. Within this melodic compass, or the musical space of three octaves and a quarter, lie the voices of all the other crawling six-footed symphonizers. How is all this music produced? Men and the higher animals have lungs—the bellows; a windpipe; a larynx, the real sounding instrument; and, as mouth-piece, the hollow of the throat and mouth. How can insects, too, execute vocal music? The answer is simple: no insect has what we in the proper sense call a voice. They produce their music either like our bumble-bee, by the mere vibration of their wings, or they have some special apparatus which they adapt to musical efforts, the peculiarities of which we are about to learn from some of them.
As we continue our walk, our feet, treading down the grass, cause a lively disturbance, like that which Gulliver raised among the Lilliputians. Every sort of frightened thing, large and small, hops up and down in front of us, behind us, to the right and left. But, out of the confusion of sounds that accompany the disturbance, there strikes upon us, over-sounding all, a sharp rattling every child knows the musician the green jumper of the meadows, the grasshopper. What is the instrument that this animal plays upon? The grasshopper is a real fiddler. To satisfy ourselves of this, we have only to catch one and examine him closely, to find that he carries the instrument on which he plays upon his thigh. In our picture (Fig. 1) the inner side of the grasshopper's thigh is represented as turned toward us, and over it is drawn a curious skin. If we bring a section of this skin under a microscope
|Fig. 1.—Grasshopper's Leg (magnified three times).||Fig. 2.—Toothed Skin of the Grasshopper's Leg (magnified one hundred times).|
magnifying about a hundred times, we shall perceive that the cellular tissue of which it consists is furnished with several small teeth (Fig. 2). They are not much longer than a hair is thick, but there are eighty or ninety of them. This system is the grasshopper's fiddle-bow. The insect has other peculiar formations on each wing; these, however, have no teeth, but are even, and project as an edging along the wing. When the grasshopper would make music, he rubs his fiddle-bow rapidly backward and forward over this process, and there arises the well-known rattling sound, such as one can produce with a bow upon loosely strung violin-strings. The tone, which is strengthened by the action of the wing as a resonance membrane, is not the same with every individual. We hear, sometimes the first, sometimes the second violin, sometimes the bass-viol; and Handel seems to have had the last especially in his mind when, in his Oratorio, Israel in Egypt, he attempted to represent the rushing of the swarms of locusts which afflicted the Nile country as the seventh plague, by a principal viola.
Several other species of insects have apparatus for producing sounds similar to that of the grasshopper, or modifications of it. Of a different type is that with which the cicadas (Fig. 3) are endowed—the only creatures of this class which have vocal apparatus analogous to those of the higher animals. Only the males of this family are singers, for which the Greek poets called them happy because their females were dumb. With the ancients, a cicada sitting on a harp was the symbol of music. A pretty fable tells of the contest between two cithara-players, in which the curious event happened that when one of the contestants broke a string, a singing cicada sprang on his harp and helped him out so that he gained the prize. The Greeks, who shut the insects in cages so as to be sung to by them in their sleep, were at odds concerning the nature of their singing apparatus; and the controversy among naturalists on the subject lasted till Fig. 4.—Tone Apparatus of the Cicada (magnified thirty times). very recently. The zoölogist H. Landois, who investigated the difficult subject of animal sounds with ceaseless industry and great skill, was able to give a satisfactory solution to the question. According to his research, the case is one in which the sound is really made by air circulating through passages in the interior of the body. Every insect's body is penetrated by a system of breathing-tubes or tracheae which open at places on the surface. The openings are called stigmata. This system of breathing-tubes, through which the air is inspired and expired, takes the place of the lung of the higher animals. Landois discovered them in very obscure parts of the cicada, and found that they form a kind of windpipe representing the actual tone-factory of the animals. This air cavity is, as the picture (Fig. 4) shows, not quite open, but has only a narrow cleft (sp), through which the air goes in and out. The cleft is formed by two stretched membranes (sa and sb), which vibrate when the air passes through. They serve, in fact, a like function with the vocal cords of our larynx. They lie, besides, opposite a large cavity over which a folded membrane is stretched like a drum-head upon a hard ring, and which, when the vocal cords begin to vibrate, vibrates with them and serves as a resonance apparatus. Although there is no real voice, which with us is inseparable from a mouth, we can say that the cicada comes nearest among insects to having such a gift There is a curious relative of our cicada in America, which in its larval condition exhibits a phenomenon that nothing else is like. The larva lives in that form fully seventeen years under ground before it assumes the shape of a perfect insect. It has been called by the characteristic name of the seventeen-year locust. The voice of this locust was heard on board the Beagle, in which Darwin made his famous voyage, an English mile off. Its song is essentially a trill of the treble E with D sharp, then a run down the chromatic scale and rapidly up again, about such a strain as one would play if he slipped his finger up and down the string of a violin while drawing the bow over it. The musical reader may gain from the following an idea of the talent as a composer, and of the song of this locust:
With most musical insects there is no special apparatus for the production of tones. They simply combine the useful with the agreeable. The wings that bear them through the air also make the sound-waves. The only remarkable thing is, that the flying-tones thus produced are so different in single kind. The wings of the bee, for example, vibrate four hundred and forty times in a second—the same number of vibrations as in our normal tone; it is the music-master, and is the cleverest and best esteemed of insects. In other bees, as the female bumble-bee, the wings vibrate eight hundred and seventy times in a second, and sound the treble A, an octave higher than the bee. Marey, who has succeeded in photographing the flight of birds, has also found an ingenious method of determining the number of vibrations of insects' wings. He fixed a fly so that the extreme tip of its wing touched a soot-blackened cylinder, which could be turned by clock-work upon its axis. Every stroke of the wing made a faint but perceptible mark, by means of which Marey was able to deter-mine that the fly made three hundred and thirty wing-beats in a second.
As we sit at night by the lamp, there arises suddenly a loud humming tone, alternately swelling to considerable strength and diminishing till it is barely heard, until the musician, a large blue-bottle fly, to our annoyance darts humming against our cheek or hand, or precipitates himself into the lamp. Every reader has had occasional opportunities, of which these are instances, to enjoy the study of such examples of the capacity of insect sounds to make music.—Translated for The Popular Science Monthly from Ueber Land und Meer.