The right wing-cover overlaps the left.  Its inner edge carries, on the under side, near the base, a callosity from which five radiating nervures proceed; two of them upwards and two downwards, while the fifth runs approximately at right angles to these.  This last nervure, which is of a slightly reddish hue, is the fundamental element of the musical device; it is, in short, the bow, the fiddlestick, as is proved by the fine notches which run across it.  The rest of the wing-cover shows a few more nervures of less importance, which hold the membrane stretched tight, but do not form part of the friction apparatus.

The left or lower wing-cover is of similar structure, with the difference that the bow, the callosity, and the nervures occupy the upper face.  It will be found that the two bows—­that is, the toothed or indented nervures—­cross one another obliquely.

When the note has its full volume, the wing-covers are well raised above the body like a wide gauzy sail, only touching along the internal edges.  The two bows, the toothed nervures, engage obliquely one with the other, and their mutual friction causes the sonorous vibration of the two stretched membranes.

[Illustration:  THE ITALIAN CRICKET.]

The sound can be modified accordingly as the strokes of each bow bear upon the callosity, which is itself serrated or wrinkled, or on one of the four smooth radiating nervures.  Thus in part are explained the illusions produced by a sound which seems to come first from one point, then from another, when the timid insect is alarmed.

The production of loud or soft resounding or muffled notes, which gives the illusion of distance, the principal element in the art of the ventriloquist, has another and easily discovered source.  To produce the loud, open sounds the wing-covers are fully lifted; to produce the muted, muffled notes they are lowered.  When lowered their outer edges press more or less lightly on the soft flanks of the insect, thus diminishing the vibratory area and damping the sound.

The gentle touch of a finger-tip muffles the sharp, loud ringing of a glass tumbler or “musical-glass” and changes it into a veiled, indefinite sound which seems to come from a distance.  The White Cricket knows this secret of acoustics.  It misleads those that seek it by pressing the edge of its vibrating membranes to the soft flesh of its abdomen.  Our musical instruments have their dampers; that of the OEcanthus pellucens rivals and surpasses them in simplicity of means and perfection of results.

The Field-Cricket and its relatives also vary the volume of their song by raising or lowering the elytra so as to enclose the abdomen in a varying degree, but none of them can obtain by this method results so deceptive as those produced by the Italian Cricket.

To this illusion of distance, which is a source of perpetually renewed surprise, evoked by the slightest sound of our footsteps, we must add the purity of the sound, and its soft tremolo.  I know of no insect voice more gracious, more limpid, in the profound peace of the nights of August.  How many times, per amica silentia lunae, have I lain upon the ground, in the shelter of a clump of rosemary, to listen to the delicious concert!