There is nothing new in this experiment; the find has been dealt with just as though it lay upon soil unsuitable for burial. The fall is the result of an attempt to transport the load.
The time has come to set up the Frog's gibbet celebrated by Gledditsch. The batrachian is not indispensable; a Mole will serve as well or even better. With a ligament of raphia I fix him, by his hind-legs, to a twig which I plant vertically in the ground, inserting it to no great depth. The creature hangs plumb against the gibbet, its head and shoulders making ample contact with the soil.
The gravediggers set to work beneath the part which lies upon the ground, at the very foot of the stake; they dig a funnel-shaped hole, into which the muzzle, the head and the neck of the mole sink little by little. The gibbet becomes uprooted as they sink and eventually falls, dragged over by the weight of its heavy burden. I am assisting at the spectacle of the overturned stake, one of the most astonishing examples of rational accomplishment which has ever been recorded to the credit of the insect.
This, for one who is considering the problem of instinct, is an exciting moment. But let us beware of forming conclusions as yet; we might be in too great a hurry. Let us ask ourselves first whether the fall of the stake was intentional or fortuitous. Did the Necrophori lay it bare with the express intention of causing it to fall? Or did they, on the contrary, dig at its base solely in order to bury that part of the mole which lay on the ground? that is the question, which, for the rest, is very easy to answer.
The experiment is repeated; but this time the gibbet is slanting and the Mole, hanging in a vertical position, touches the ground at a couple of inches from the base of the gibbet. Under these conditions absolutely no attempt is made to overthrow the latter. Not the least scrape of a claw is delivered at the foot of the gibbet. The entire work of excavation is accomplished at a distance, under the body, whose shoulders are lying on the ground. There—and there only—a hole is dug to receive the free portion of the body, the part accessible to the sextons.
A difference of an inch in the position of the suspended animal annihilates the famous legend. Even so, many a time, the most elementary sieve, handled with a little logic, is enough to winnow the confused mass of affirmations and to release the good grain of truth.
Yet another shake of the sieve. The gibbet is oblique or vertical indifferently; but the Mole, always fixed by a hinder limb to the top of the twig, does not touch the soil; he hangs a few fingers'-breadths from the ground, out of the sextons' reach.
What will the latter do? Will they scrape at the foot of the gibbet in order to overturn it? By no means; and the ingenuous observer who looked for such tactics would be greatly disappointed. No attention is paid to the base of the support. It is not vouchsafed even a stroke of the rake. Nothing is done to overturn it, nothing, absolutely nothing! It is by other methods that the Burying-beetles obtain the Mole.
These decisive experiments, repeated under many different forms, prove that never, never in this world do the Necrophori dig, or even give a superficial scrape, at the foot of the gallows, unless the hanging body touch the ground at that point. And, in the latter case, if the twig should happen to fall, its fall is in nowise an intentional result, but a mere fortuitous effect of the burial already commenced.
What, then, did the owner of the Frog of whom Gledditsch tells us really see? If his stick was overturned, the body placed to dry beyond the assaults of the Necrophori must certainly have touched the soil: a strange precaution against robbers and the damp! We may fittingly attribute more foresight to the preparer of dried Frogs and allow him to hang the creature some inches from the ground. In this case all my experiments emphatically assert that the fall of the stake undermined by the sextons is a pure matter of imagination.