A loud noise stifles a feeble note and prevents it from being heard; a brilliant light eclipses a feeble glimmer. Heavy waves overcome and obliterate ripples. In the two cases cited we have waves of the same nature. But a clap of thunder does not diminish the feeblest jet of light; the dazzling glory of the sun will not muffle the slightest sound. Of different natures, light and sound do not mutually interact.
My experiment with spike-lavender, naphthaline, and other odours seems to prove that odour proceeds from two sources. For emission substitute undulation, and the problem of the Great Peacock moth is explained. Without any material emanation a luminous point shakes the ether with its vibrations and fills with light a sphere of indefinite magnitude. So, or in some such manner, must the warning effluvium of the mother Oak Eggar operate. The moth does not emit molecules; but something about it vibrates, causing waves capable of propagation to distances incompatible with an actual diffusion of matter.
From this point of view, smell would have two domains—that of particles dissolved in the air and that of etheric waves. The former domain alone is known to us. It is also known to the insect. It is this that warns the Saprinidae of the fetid arum, the Silphidae and the Necrophori of the putrid mole.
The second category of odour, far superior in its action through space, escapes us completely, because we lack the essential sensory equipment. The Great Peacock moth and the Oak Eggar know it at the time of their nuptial festivities. Many others must share it in differing degrees, according to the exigencies of their way of life.
Like light, odour has its X-rays. Let science, instructed by the insect, one day give us a radiograph sensitive to odours, and this artificial nose will open a new world of marvels.
Some of our machines have extraordinary-looking mechanisms, which remain inexplicable so long as they are seen in repose. But wait until the whole is in motion; then the uncouth-looking contrivance, with its cog-wheels interacting and its connecting-rods oscillating, will reveal the ingenious combination in which all things are skilfully disposed to produce the desired effects. It is the same with certain insects; with certain weevils, for instance, and notably with the Acorn-beetles or Balanini, which are adapted, as their name denotes, to the exploitation of acorns, nuts, and other similar fruits.
The most remarkable, in my part of France, is the Acorn Elephant (Balaninus elephas, Sch.). It is well named; the very name evokes a mental picture of the insect. It is a living caricature, this beetle with the prodigious snout. The latter is no thicker than a horsehair, reddish in colour, almost rectilinear, and of such length that in order not to stumble the insect is forced to carry it stiffly outstretched like a lance in rest. What is the use of this embarrassing pike, this ridiculous snout?