Social Life in the Insect World

by Jean-Henri Fabre

The dampers do not overlap; on the contrary, they are separated by a fairly wide interval. With the rigid tongues, appendages of the abdomen, they half shelter the cymbals, half of which is completely bare. Under the pressure of the finger the abdomen opens a little at its articulation with the thorax. But the insect is motionless when it sings; there is nothing of the rapid vibrations of the belly which modulate the song of the common Cigale. The chapels are very small; almost negligible as resonators. There are mirrors, as in the common Cigale, but they are very small; scarcely a twenty-fifth of an inch in diameter. In short, the resonating mechanism, so highly developed in the common Cigale, is here extremely rudimentary. How then is the feeble vibration of the cymbals re-enforced until it becomes intolerable?

This species of Cigale is a ventriloquist. If we examine the abdomen by transmitted light, we shall see that the anterior two-thirds of the abdomen are translucent. With a snip of the scissors we will cut off the posterior third, to which are relegated, reduced to the strictly indispensable, the organs necessary to the propagation of the species and the preservation of the individual. The rest of the abdomen presents a spacious cavity, and consists simply of the integuments of the walls, except on the dorsal side, which is lined with a thin muscular layer, and supports a fine digestive canal, almost a thread. This large cavity, equal to nearly half the total volume of the insect, is thus almost absolutely empty. At the back are seen the two motor muscles of the cymbals, two muscular columns arranged like the limbs of a V. To right and left of the point of this V shine the tiny mirrors; and between the two branches of muscle the empty cavity is prolonged into the depths of the thorax.

This empty abdomen with its thoracic annex forms an enormous resonator, such as no other performer in our countryside can boast of. If I close with my finger the orifice of the truncated abdomen the sound becomes flatter, in conformity with the laws affecting musical resonators; if I fit into the aperture of the open body a tube or trumpet of paper the sound grows louder as well as deeper. With a paper cone corresponding to the pitch of the note, with its large end held in the mouth of a test-tube acting as a resonator, we have no longer the cry of the Cigale, but almost the bellowing of a bull. My little children, coming up to me by chance at the moment of this acoustic experiment, fled in terror.

The grating quality of the sound appears to be due to the little tongues which press on the nervures of the vibrating cymbals; the cause of its intensity is of course the ample resonator in the abdomen. We must admit that one must truly have a real passion for song before one would empty one's chest and stomach in order to make room for a musical-box. The necessary vital organs are extremely small, confined to a mere corner of the body, in order to increase the amplitude of the resonating cavity. Song comes first of all; other matters take the second rank.

It is lucky that the Cacan does not follow the laws of evolution. If, more enthusiastic in each generation, it could acquire, in the course of progress, a ventral resonator comparable to my paper trumpets, the South of France would sooner or later become uninhabitable, and the Cacan would have Provence to itself.

After the details already given concerning the common Cigale it is hardly needful to tell you how the insupportable Cacan can be reduced to silence. The cymbals are plainly visible on the exterior. Pierce them with the point of a needle, and immediately you have perfect silence. If only there were, in my plane-trees, among the insects which carry gimlets, some friends of silence like myself, who would devote themselves to such a task! But no: a note would be lacking in the majestic symphony of harvest-tide.

We are now familiar with the structure of the musical organ of the Cigale. Now the question arises: What is the object of these musical orgies? The reply seems obvious: they are the call of the males inviting their mates; they constitute a lovers' cantata.

I am going to consider this reply, which is certainly a very natural one. For thirty years the common Cigale and his unmusical friend the Cacan have thrust their society upon me. For two months every summer I have them under my eyes, and their voice in my ears. If I do not listen to them very willingly I observe them with considerable zeal. I see them ranged in rows on the smooth rind of the plane-trees, all with their heads uppermost, the two sexes mingled, and only a few inches apart.

The proboscis thrust into the bark, they drink, motionless. As the sun moves, and with it the shadow, they also move round the branch with slow lateral steps, so as to keep upon that side which is most brilliantly illuminated, most fiercely heated. Whether the proboscis is at work or not the song is never interrupted.

Now are we to take their interminable chant for a passionate love-song? I hesitate. In this gathering the two sexes are side by side. One does not spend months in calling a person who is at one's elbow. Moreover, I have never seen a female rush into the midst of even the most deafening orchestra. Sight is a sufficient prelude to marriage, for their sight is excellent. There is no need for the lover to make an everlasting declaration, for his mistress is his next-door neighbour.