7
One cannot mention, even casually, the numberless industries, nearly all of absorbing interest, exercised among the rocks, under the ground, in the walls, on the branches, the grass, the flowers, the fruits and down to the very bodies of the subjects studied; for we sometimes find a treble superposition of parasites, as in the Oil-beetles; and we see the maggot itself, the sinister guest at the last feast of all, feed some thirty brigands with its substance.
Among the Hymenoptera, which represent the most intellectual class in the world which we are studying, the building-talents of our wonderful Hive-bee are certainly equalled, in other orders of architecture, by those of more than one wild and solitary bee and notably by the Megachile, or Leaf-cutter, a little insect which is nothing to look at and which, to house its eggs, manufactures honey-pots formed of a multitude of disks and ellipses cut with mathematical precision from the leaves of certain trees. For lack of space, I am unable, to my great regret, to quote the beautiful and pellucid pages which Fabre, with his usual conscientiousness, devotes to the exhaustive study of this admirable work; nevertheless, since the occasion offers, let us listen to his own words, though it be but for a moment and in regard to a single detail:
“With the oval pieces, it becomes another matter. What model has the Megachile when cutting her neat ellipses out of the delicate material for her wallets, the robinia-leaves? What ideal pattern guides her scissors? What system of measurement tells her the dimension? One would like to picture the insect as a living pair of compasses, capable of tracing an elliptic curve by a certain natural inflexion of its body, even as our arm traces a circle by swinging from the shoulder. A blind mechanism, the mere outcome of its organization, would alone be responsible for its geometry. This explanation would tempt me if the large oval pieces were not accompanied by much smaller ones, also oval, which are used to fill the empty spaces. A pair of compasses which changes its radius of its own accord and alters the curve according to the plan before it appears to me an instrument somewhat difficult to believe in. There must be something better than that. The circular pieces of the lid suggest it to us.
“If, by the mere flexion inherent in her structure, the Leaf-cutter succeeds in cutting out ovals, how does she manage to cut out rounds? Can we admit the presence of other wheels in the machinery for the new pattern, so different in shape and size? However, the real point of the difficulty does not lie there. Those rounds, for the most part, fit the mouth of the jar with almost exact precision. When the cell is finished, the bee flies hundreds of yards away to make the lid. She arrives at the leaf from which the disk is to be cut. What picture, what recollection has she of the pot to be covered? Why, none at all: she has never seen it; she does her work underground, in utter darkness! At the utmost, she can have the indications of touch: not actual indications, of course, for the pot is not there, but past indications, useless in a work of precision. And yet the disk to be cut out must have a fixed diameter: if it were too large, it would not go in; if too small, it would close badly, it would slip down on the honey and suffocate the egg. How shall it be given its correct dimensions without a pattern? The bee does not hesitate for a moment. She cuts out her disk with the same celerity which she would display in detaching any shapeless lobe that might do for a stopper; and that disk, without further measurement, is of the right size to fit the pot. Let whoso will explain this geometry, which in my opinion is inexplicable, even when we allow for memory begotten of touch and sight.”
Let us add that the author calculated that, to form the cells of a kindred Megachile, the Silky Megachile, exactly 1,064 of these ellipses and disks would be required; and they must all be collected and shaped in the course of an existence that lasts a few weeks.