Boring into wood is a favourite proceeding on the part of many small creatures, insects, shrimps, and ship-worms, by which they not only acquire nourishment, but at the same time penetrate more and more deeply into safe quarters and concealment. It is not surprising that it has become the necessary and regular mode of life of a host of small animals, and consequently that man who wants wood in good sound blocks and planks for his various constructions is a good deal put out by the voracity of the wood-boring community. To some extent he has given up the task of checking their proceedings, and now uses metal where he formerly used wood, but that only applies to a limited field. Wood is still the great material of rough construction, and the main substance used in fittings and furniture.

In our own country and in most parts of the world there are large grubs or caterpillars, such as those of the goat moth, three inches long and as thick as one’s finger, which eat into the stems of trees and spoil the timber. The grub of the handsome moth known as the wood leopard is another of these. It attacks poplar trees, and we used to take it in numbers in the London parks and squares when I was a collector. The goat moth is specially destructive to willow trees. But there are a very large series of smaller grubs and adult insects which injure trees or bore or devour wood already cut and dried. Among these are the saw-flies and a number of beetles, and in Sicily and the tropics there are the wonderful white ants which are not ants at all, but more like May-flies. The destruction caused by these borers and eaters of wood is increased by the fact that when they have riddled a piece of wood, moisture penetrates it, and vegetable “moulds” flourish within it and complete the break-up. Among the most destructive borers of wood are those which attack the ships and piers of wood placed by man in the sea. These are certain shell-fish, called ship-worms (Teredo), which are really peculiarly modified mussels. There is also a tiny shrimp-like creature, the Limnoria terebrans, which does enormous damage by its borings to piers of wood erected in the sea. True insects do not flourish in the sea. There are marine bivalve shell-fish which bore into clay, sandstone, chalk, and even into hard granite-like rock. They do not use jaws or teeth for this purpose, but the surface of their shells, which are sharp and spiny, and also the sand which adheres to their soft muscular bodies like emery powder to the pewter-plate of a lapidary’s wheel. You may see the large and small holes made by Pholas (called also “the piddock”) and other bivalve shell-fish in the clay and chalk rocks of the seashore on most parts of the English coast.

Most boring animals swallow the material which they excavate in the act of boring, just as the earth-worm swallows the soil into which it bores, and as many sand-worms do, throwing out from the hind end of the body, in the form of a little coiled-up heap, a vast quantity of undigested matter which has passed through them. But many insects which swallow some of the material disengaged by their jaws remove, in addition, a large quantity which is ejected from the boring as powder, like sawdust, and others do not swallow any of the material into which they bore. So, too, the Pholas and marine-boring mussels do not swallow the material which they loosen. It is a very slow process, the boring in rock, and the fine particles rubbed away by incessant movement are carried off in the sea-water.

To some extent the marine creatures which bore in rocks seem to be helped by chemical action, since they show a preference for chalk and limestone, easily dissolved by weak acid secreted by the borer, though, clearly enough, they are not dependent on such chemical aid since we find them also boring in insoluble granite rock and shale and clay. There is one true worm-borer which perforates hard limestone pebbles and chalk rocks, so as to give them the appearance which we call “worm-eaten” when caused by another sort of worm and observed in a very different material, namely, old furniture and woodwork. At Tenby, in South Wales, the limestone pebbles on the beach are quite commonly riddled with these worm-holes, truly “worm-eaten.” When they are not too abundant one can see that the holes are arranged in pairs like a figure 8, about half the size here printed. On splitting the rock or stone one finds a deeply-running U-shaped double tube excavated in the stone. In this the little worm lived. It is easiest to get at the worms in a fresh and living state on a coast where there are chalk-rocks and sea-washed lumps of chalk. The chalk is easy to split and cut at low tide, and then the little key-hole apertures can be broken across and the soft red worm extracted. It is a beautiful red-blooded little worm—little more than half an inch long—with two tactile horns on its head and little bristles and gills on the rings of its annulated body. It is a true “worm,” like the earth-worm, what naturalists call by the not displeasing name an “annelid.” It seems at first sight impossible that this delicate little thing should “worm-eat” the hardest limestone. It has no jaws, but one of the rings or segments of the front part of the body has two of its bristles swollen to relatively gigantic size, hard and black. These are its boring organs, but I have no doubt that it is helped, especially in its young state when commencing to bore, by an acid secretion from the surface of the body.

Curiously enough, in the strict sense of the word “worm,” the boring of chalk and stones by the little marine creature just mentioned (whose name is Polydora) is the only instance of a “worm-eaten” condition being produced by a real worm. The worm-eaten condition of wood is produced either by the grub of a minute beetle (which is not in the strict sense a “worm”) or by an ingenious human maker of “antiques” who imitates the little holes on the surface of the woodwork of old furniture, so as to pass off clever reproductions for really ancient cabinet work. The little holes to imitate those of the true insect furniture-borer are sometimes produced by discharging a gun loaded with fine shot at the piece of furniture which is to be passed off as ancient. But knowing purchasers probe the holes so made with a carpet needle, and discover the lead-shot sunk in the wood. Hence there has arisen a profession of specially-skilled “worm-eaters,” who, by careful boring, imitate the holes made by insect grubs.

And now we come at last to the actual, real furniture worm or grub. It is the grub of a small beetle—the Anobium domesticum, scarcely one-fifth of an inch long (Fig. 62c), greyish-brown in colour, of a cylindrical shape, with the head completely concealed or overhung by the next division of the body, the thorax. The grubs are longer, soft, pale, and fleshy. The sign of the presence of the Anobium in your furniture is the existence of small circular holes here and there on the surface of the wood, with occasionally a little heap of yellow dust on the ground beneath them. This last sign is in fact the only proof you can have that the holes are not ancient and the burrows deserted, and that the enemy is still alive and at work. Rarely, if ever, can you see either the grub or the completed beetle into which it changes after forming a cocoon within the burrows, for they very seldom leave their excavations. But if you break up the wood you will find a surprising number of long, cylindrical passages, running side by side, and for many inches, through the deeper part of the wood, so that it may be quite rotten and ready to crumble, although presenting an uninjured surface save for the little round holes here and there. In these passages you will find both the grubs and the adult beetles.

A closely-allied and somewhat smaller species of Anobium common in houses is of a more voracious character, not confining itself to dry wood, but eating bread, biscuits, rhubarb, ginger, and even cayenne pepper. This second kind, called Anobium paniceum, is the real “book-worm”; it gets into old libraries, and the grubs bore their cylindrical tunnels from cover to cover of the undisturbed volumes. In a public library twenty-seven folio volumes standing side by side were perforated in a straight line by one individual Anobium grub or book-worm, and so regular was the tunnel thus eaten out that a string could be passed through the whole length of it, and the entire set of twenty-seven volumes lifted up at once by it.

There are one or two other grubs which less commonly injure books, and pass as “book-worms.” But the most notable of the insect enemies of books and papers is a curious little wingless insect which never passes through a grub stage of existence, but hatches out in the complete form of his parents. He is about a third of an inch long, has the shape of an elongated kite, with a long tail and six legs, and is called by old writers “the silver-fish,” and by entomologists Lepisma (Fig. 63). This little pest does not burrow, but nibbles, and has destroyed many a valuable old document and ancient book. Paste and sugar are a great attraction to him, and he will destroy a boxful of printed labels or a valuable manuscript, leaving only the ink-marked parts untouched, but ready to crumble.

Closely allied to the book-worm beetle, Anobium, is a larger beetle, called Xestobium tessellatum (Fig. 62 a) which infests old woodwork, its grubs making correspondingly larger tunnels. The entire woodwork of a house has had to be removed and replaced in consequence of this creature’s depredation, and such pieces of furniture as a four-post bedstead have been riddled and made rotten in two or three years by its burrowing. It is still common in England in old wood-panelled rooms and in wooden mantelpieces. The most interesting fact about it is that it is the maker of those nocturnal tappings which are known as the “death-watch.” It is the beetle itself (Fig. 62 a), not the grub, which makes these sounds. It makes them by deliberately striking the wood on which it stands, with its head. The taps are usually from five to seven in quick succession, the sound dying away in intensity in the later strokes. A second, and even a third, beetle will then reply with similar taps from the woodwork of some other part of the room. Years ago I used to be gently lulled to sleep by these “raps” in my rooms at Oxford, accompanied by the sound of spasmodic rushes of mice behind the woodwork. At first I thought the tapping was caused by the falling of drops of water through a leaky roof, but soon ascertained the actual cause. One does not notice these tappings until the dead of night when all else is still, and they are so mysterious and persistent that one can understand superstition arising in connection with them, and that the nerves of any one already overwrought, might be so affected by them as to lead to the belief that evil spirits are “rapping,” or that a ghostly coffin is being nailed together for a dying man. The little beetle has often been tracked by a naturalist, and discovered in some concealed position nodding its diminutive but hard head with sharp jerks, and producing an almost incredible volume of sound in proportion to its size. If the beetle, when discovered, is kept in captivity in a wooden box, it is easy to set it “tapping” or “rapping” by tapping oneself with a pencil on the table on which the box is placed, when the faithful little death-watch will unfailingly reply. Possibly some of the “raps” recorded by the pioneers of spirit-rapping, when not produced by the toes of designing mediums like the young ladies of Rochester, N.Y., were actually made by death-watch beetles. It is certain that the somewhat eccentric supposition that disembodied spirits endeavour to make signals to living humanity by “rapping” owes its origin (long before the nineteenth-century craze for “spirit-rapping”) to the measured tap-tap-tapping of the death-watch beetle, and the consequent superstition at a time when the beetle was not known to be the “tapper.”

Whilst the bigger beetle, Xestobium, is the common death-watch, it has been proved that the little furniture beetle, Anobium, is also a tapper, making regular and persistent strokes like the ticking of a watch. Another insect, called the book-louse (Atropos divinatoria), very minute, only one-twentieth of an inch, soft, white, and wingless, not a beetle at all, but also a devourer of literature (Fig. 64), is declared by some good observers to be a “ticker” or “tapper,” but other naturalists deny that it can make such sounds. It seems unlikely on account of the extremely small size and softness of the book-louse, but the matter needs further investigation.

A curious fact is that the grubs of beetles such as Anobium and Xestobium (or other closely allied kinds) are not arrested in their tunnelling by soft metal. They cannot tackle iron plate or brass sheeting, but they will penetrate tinfoil and, what is more astonishing, lead plate and leaden waterpipes. Specimens showing such perforations are in the museums of Oxford and London, and I have received an account of a lead pipe packed in wood in the wall of a house being perforated by these beetle-grubs. Once at work on the wood, “the straightforward intentions” of the grub are not to be diverted by such an obstacle as lead: it goes straight on through the lead as it would through the cover of a book or a knot in the wood.

I have sometimes been asked to give advice as to the best method of destroying the furniture worm or grub. If the piece of furniture (or its pieces) can without injury be “baked” in a hot chamber for twenty-four hours, at a temperature a little above that of boiling water, that is the easiest method of destroying the pest. Or, again, I should suggest placing the piece of furniture in a refrigerating chamber for a week or two. If neither of these methods can be used, the piece of furniture should be placed in a very hot room, and creosote or bisulphide of carbon or solution of cyanide of potassium should be injected with a very fine-nosed syringe into the little circular holes of the burrows on the surface of the wood; then the piece of furniture must be at once exposed to the cold, which will cause the air to be drawn into the burrows and diffuse the volatile poison within. The “worm holes” on the surface should, as soon as the piece of furniture is quite cold, be closed by melted paraffin. If the piece of wood which it is desired to “cure” will stand submersion in water for a few minutes, and is not larger than a cricket bat, it is, of course, easy, by first warming it through and then plunging it into water containing corrosive sublimate or other poison, fairly to impregnate the burrows, and make an end of the beetles and their grubs. Painting is the common and approved means of protecting wood against these attacks, and in some positions metal sheathing is used. The method most largely used for protecting wood in the open air against “worm” and “mould” is that of forcing creosote into its pores—an improvement on the old system of painting with coal tar. A more expensive but beautiful method of protecting wood is to force hard paraffin in a melted condition by pressure into the pores. The wood becomes wonderfully firm and waterproof. Neither damp and mould, nor boring insect, nor shrimp can then penetrate it. This method was introduced some years ago, but I do not know whether it has been largely used.