TOOLS.
CHAPTER III.
BORING TOOLS.—STRIKING TOOLS.—GRASPING TOOLS.
The Bradawl and the Gimlet defined.—Natural Bradawls.—The Ichneumon-flies.—A Pimpla engaged in Boring Operations.—Principle of the Wedge.—Resisting Power of Earth.—Pitching Tents in Sand.—Hidden Forces of Nature.—The Aloe-leaf and its Growth.—A cruel Punishment.—Natural Gimlets.—Ovipositor of the Sirex, and its Analogy to a Carpenter’s Gimlet.—The Auger and the Gad-fly.—Striking Tools.—The Hammer.—Origin and Development of the Tool.—The Axe.—The Woodpecker and the Nuthatch.—The Ivory-billed Woodpecker.—Grasping Tools.—Pincers and their Modifications.—Sugar-tongs and Coal-tongs.—Natural Pincers.—Bivalve Molluscs.—The Clam’s Grip.—The Earwig.—Crab and Lobster Claws.
Boring Tools.
NEXT in importance to the edged tools which cut, come the pointed tools by which holes can be bored. We have an abundance of such tools, but they can all be reduced to two types, namely, those which, like the Bradawl, are forced between the fibres, and those which, like the Gimlet, cut away the material as they pass through it.
They may, again, be shown to be different modifications of a single principle—i.e. that of the Wedge or Inclined Plane, which, as has already been shown, is identical with that of the screw. The Bradawl is, in fact, a sharp wedge, which is forced through the fibres, sometimes being merely forced between them, and sometimes cutting them, and thus forcing aside the severed fibres.
A natural example of the Bradawl is to be found in various Ichneumon-flies, especially those with very long ovipositors, which are intended for boring into wood.
All the Ichneumons are parasitic, laying their eggs in the larvæ of other insects, mostly those of moths and butterflies. Generally these larvæ exist in the open air, and the Ichneumon-fly has little difficulty in piercing them. But there are some which live either in wood or underground, and, in order to reach their hidden bodies, the Ichneumon is furnished with an extremely long and sharply pointed ovipositor.
This wonderful instrument is not so thick as an ordinary horsehair, although it is composed of three portions, and seems to be utterly inadequate to the task which it has to perform. Ascertaining by its instinct the exact locality of the caterpillar which it desires to pierce, the Ichneumon-fly clings firmly to the tree, bends the body so as to bring the point of the ovipositor against the wood, and, by moving the abdomen backwards and forwards, gradually works the instrument into the wood, sometimes piercing it to a considerable depth.
Mr. Westwood once saw an Ichneumon-fly thus boring its way into a dry post, the wood of which must have been very hard. When she had bored far enough, she partially withdrew the ovipositor, and then re-plunged it into the hole that she had made, as if she were depositing eggs. While engaged in this operation, she stood very high on her long legs, resting only on the extremities of the feet. She belonged to the genus Pimpla.
The principle of the Wedge or Inclined Plane is admirably shown by objects which we pass unheeded every day, and yet afford wonderful examples of the power of the wedge.