The Common Cicada is the biggest of the five, the most popular and the one whose musical apparatus is usually described. Under the male’s chest, immediately behind the hind-legs, are two large semicircular plates, overlapping each other slightly, the right plate being on the top of the left. These are the shutters, the lids, the dampers, in short the opercula of the organ of sound. Lift them up. You then see opening, on either side, a roomy cavity, known in Provence by the name of the chapel (li capello). The two together form the church (la glèiso). They are bounded in front by a soft, thin, creamy-yellow membrane; at the back by a dry pellicle, iridescent as a soap-bubble [[60]]and called the mirror (mirau) in the Provençal tongue.
The church, the mirrors and the lids are commonly regarded as the sound-producing organs. Of a singer short of breath it is said that he has cracked his mirrors (a li mirau creba). Picturesque language says the same thing of an uninspired poet. Acoustics give the lie to the popular belief. You can break the mirrors, remove the lids with a cut of the scissors, tear the yellow front membrane and these mutilations will not do away with the Cicada’s song: they simply modify it, weaken it slightly. The chapels are resonators. They do not produce sound, they increase it by the vibrations of their front and back membranes; they change it as their shutters are opened more or less wide.
The real organ of sound is seated elsewhere and is not easy to find, for a novice. On the other side of each chapel, at the ridge joining the belly to the back, is a slit bounded by horny walls and masked by the lowered lid. Let us call it the window. This opening leads to a cavity or sound-chamber deeper than the adjacent chapel, but much less wide. Immediately behind the attachment of the [[61]]rear wings is a slight, almost oval protuberance, which is distinguished by its dull-black colour from the silvery down of the surrounding skin. This protuberance is the outer wall of the sound-chamber.
Let us make a large cut in it. We now lay bare the sound-producing apparatus, the cymbal. This is a little dry, white membrane, oval-shaped, convex on the outside, crossed from end to end of its longer diameter by a bundle of three or four brown nervures, which give it elasticity, and fixed all round in a stiff frame. Imagine this bulging scale to be pulled out of shape from within, flattening slightly and then quickly recovering its original convexity owing to the spring of its nervures. The drawing in and blowing out will produce a clicking sound.
Twenty years ago, all Paris went mad over a silly toy called the Cricket, or Cri-cri, if I remember rightly. It consisted of a short blade of steel, fastened at one end to a metallic base. Alternately pressed out of shape with the thumb and then released, the said blade, though possessing no other merit, gave out a very irritating click; and nothing more was needed to make it popular. The [[62]]Cricket’s vogue is over. Oblivion has done justice to it so drastically that I doubt if I shall be understood when I recall the once famous apparatus.
The membranous cymbal and steel Cricket are similar instruments. Both are made to rattle by pushing an elastic blade out of shape and restoring it to its original condition. The Cricket was bent out of shape with the thumb. How is the convexity of the cymbals modified? Let us go back to the church and break the yellow curtain that marks the boundary of each chapel in front. Two thick muscular columns come in sight, of a pale orange colour, joined together in the form of a V, with its point standing on the insect’s median line, on the lower surface. Each of these fleshy columns ends abruptly at the top, as though lopped off; and from the truncated stump rises a short, slender cord which is fastened to the side of the corresponding cymbal.
There you have the whole mechanism, which is no less simple than that of the metal Cricket. The two muscular columns contract and relax, shorten and lengthen. By means of the terminal thread each tugs at its cymbal, pulling it down and forthwith letting [[63]]it spring back of itself. Thus are the two sound-plates made to vibrate.
Would you convince yourself of the efficacy of this mechanism? Would you make a dead but still fresh Cicada sing? Nothing could be simpler. Seize one of the muscular columns with the pincers and jerk it gently. The dead Cri-cri comes to life again; each jerk produces the clash of the cymbal. The sound is very feeble, I admit, deprived of the fulness which the living virtuoso obtains with the aid of his sound-chambers; nevertheless the fundamental element of the song is produced by this anatomical trick.
Would you on the other hand silence a live Cicada, that obstinate melomaniac who, when you hold him prisoner in your fingers, bewails his sad lot as garrulously as, just now, he sang his joys in the tree? It is no use to break open his chapels, to crack his mirrors: the shameful mutilation would not check him. But insert a pin through the side slit which we have called the window and touch the cymbal at the bottom of the sound-chamber. A tiny prick; and the perforated cymbal is silent. A similar operation on the other side renders the insect mute, though it remains as vigorous as before, showing [[64]]no perceptible wound. Any one unacquainted with the method of procedure stands amazed at the result of my pin-prick, when the utter destruction of the mirrors and the other accessories of the church does not produce silence. A tiny and in no way serious stab has an effect which is not caused even by evisceration.
The lids, those firmly fitted plates, are stationary. It is the abdomen itself which, by rising and falling, causes the church to open and shut. When the abdomen is lowered, the lids cover the chapels exactly, together with the windows of the sound-chambers. The sound is then weakened, muffled, stifled. When the abdomen rises, the chapels open, the windows are unobstructed and the sound acquires its full strength. The rapid oscillations of the belly, therefore, synchronizing with the contractions of the motor-muscles of the cymbals, determine the varying volume of the sound, which seems to come from hurried strokes of a bow.