Social Life in the Insect World eBook

This eBook from the Gutenberg Project consists of approximately 321 pages of information about Social Life in the Insect World.

Social Life in the Insect World eBook

This eBook from the Gutenberg Project consists of approximately 321 pages of information about Social Life in the Insect World.

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.

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Social Life in the Insect World from Project Gutenberg. Public domain.