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 Ichneumonfly 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.