Nature's Teachings

Another curious example of a natural door may be seen by those who will look for it.

On plants infested with aphides, or “green blight,” as the gardeners quaintly term them, may often be seen dead aphides much larger than the rest, globular, brown, and shining. These aphides have been “stung,” as it is called, by a little Ichneumon-fly belonging to the genus Ophion, and having, like all its congeners, a flat and sickle-shaped abdomen. The egg which has been laid in the aphis soon hatches, and the young Ophion absorbs into itself all the juices of the aphis. It remains within the body of its involuntary host until it is fully developed, when it cuts a tiny, but beautifully perfect circular door in the skin, and emerges, leaving the door open and still attached by its little hinge.

Considering the small size of the aphis, and that the diameter of the door is only one-eighth of the length of the insect, the perfection of its form is really remarkable.

One of the achievements of modern Architecture is the Self-closing Door, especially where it must of necessity close by its own weight, and when the fitting is so exact, that even the most experienced eye can scarcely detect it. Such a door is to be found guarding the nest of the Trap-door Spiders, several species of which are found scattered over all the warm parts of the earth. A side view of one of these extraordinary nests is given in the accompanying illustration, and on the other side is the common trap-door of our cellars.

The Spiders which make these extraordinary dwellings generally begin by excavating a nearly perpendicular tunnel in the ground. They line it with a silken web, and construct a door which exactly fits the orifice, and which is bevelled so that it shall not sink too far, and thus betray itself. I have seen and handled one, where the burrow had been sunk among lichens and mosses, and the trap-door of the nest had been most ingeniously covered with the same growths. Although the surface of the slab of earth in which the nest was made is only a few inches square, it is almost impossible to detect the entrance, so admirably do the mosses on the door correspond with those outside it.

Almost invariably the nest is sunk in the ground, but I have a specimen sent to me from India, in which the Spider must absolutely have carried the clay to a fluted pillar, burrowed in it, and then made its beautiful habitation. The nest and its inhabitant were sent to me by an officer in the 108th Regiment, accompanied by the following letter:—

“The packet contains a large Spider and the upper portion of its peculiar nest, the history of which is as follows.

“On the thirtieth of last month (September, 1870), while searching for caterpillars on a bush growing close to one of the pillars of my verandah, which is a very low one, reaching to within a foot of the ground, I saw in part of the chunam masonry at the foot of the pillar what I at first sight took to be a couple of seeds sticking to a stone. On trying to pull one off, I found that it came up with ease, bringing with it what I thought was the stone.

“But I had scarcely got it up when it was smartly pulled back. This excited my curiosity, and I raised it again with a little force. I now saw, to my wonder and admiration, that what I had fancied was a stone was a small circular door with a pretty broad hinge, made all of silk; and then distinctly observed a large black spider dart down the hole to which the above door gave an entrance. But, not knowing the depth, I broke it.

“This piece I send to you, together with its original owner, who, at the beginning of my digging operations, ran up suddenly, shut the door in my face, and hung on to it like grim death when I tried to reopen it. He soon came away with the upper piece, still keeping the door resolutely closed.”

CHAPTER II.
WALLS, DOUBLE AND SINGLE.—PORCHES, EAVES, AND WINDOWS.—THATCH, SLATES, AND TILES

The Wall and its Materials.—Bricks as they are and might be.—Trade Unionism.—Double Walls and their Uses.—Double Clothing.—The Refrigerator.—Cooking Vessels.—Fire-proof Safes.—Cocoon of the Silkworm, and its treble Walls.—Nest of the Little Ermine, Processionary, Gold-tailed, and Brown-tailed Moths.—Mud Walls.—Nests of the Termite.—Porches, Eaves, and Windows.—Nests of the Myrapetra and an Indian Ant.—The Sociable Weaver-bird and its Nest.—Thatching.—Arms of the Orang-outan.—Japanese and Chinese Rain-cloaks.—Eggs of the Gold-tailed Moth.—Action of Fur.—Slates and Tiles.—Scales of Butterfly’s Wing.—Shell of Tortoise.—Scales of Manis, Fish, and Armadillo.

WE now come to the Walls of the house, in which there is more variety than might be imagined.

Take, for example, our modern houses of the “villa” type. They are nothing but the merest shells, made of the flimsiest imaginable materials. Some years ago, while walking through a suburb where some very showy houses were being built, I amused myself by going over them and testing them. There was scarcely a room in which I could not thrust an ordinary walking-stick through the wall. When they were “finished” and “pointed,” the houses looked beautiful, but their heat in summer, cold in winter, and moisture in wet weather, can easily be imagined, especially as the sand with which the mortar was mixed had been procured from the banks of a tidal river.

There is not the least necessity for such buildings. It is absurd to run up such edifices as that, and then charge £120 per annum for rent. The whole system is as rotten as the houses, and there is nothing but prejudice and trade-unionism to prevent our houses being cool in summer, warm in winter, and dry in all weathers.

It is well known that air is practically a non-conductor of heat, and that therefore a layer of air between two very slight walls is just as warm as if the wall had been made of solid stone. Now, there are several inventions whereby the present brick could be made half its present weight, twice its present strength, hard and smooth as earthenware, so that it could not absorb water like our common brick, and pierced with holes through which air could pass.

Unfortunately, however, there is a stringent rule among brickmakers and bricklayers that they are to play into each other’s hands, and that no bricklayer is to touch a brick which has not been made in some definite district. Should he do so, he is a marked man, and will stand but little chance of getting even a day’s work.

The power of the double wall may be seen in many ways. For example, in the old days of coaching, when one had to pass hour after hour on the roof of the coach, it was known by practical experience that double body linen, and two pairs of stockings, worn one over the other, formed the best preparation for the journey. The reason was, that air became entangled between the layers of fabric, and acted as a non-conductor of heat.

Another mode of utilising the principle of the double wall is seen in the refrigerators which add so much to the comfort of the household in a hot summer. The one principle of these refrigerators is, to keep a layer of air between the ice and the surrounding atmosphere. The same principle may be used in a reverse way, and heat be preserved instead of repelled. Those cooking-pots are now well known, where half-cooked meat can be inserted in the morning, and at luncheon-time be turned out quite hot and perfectly cooked. The fact is, that the vessels in question are covered with a very thick layer of felt. The felt, however, is only a device for entangling air, and a double wall would answer the purpose as well, if not better.

The now well-known fire-resisting safes are made on this principle, and after they have been for hours in a raging fire, and the outer case has become red-hot, the interior is quite safe, the papers uninjured, and even a watch continuing to go.

Then there is the ordinary Ice-house, a sketch of which is given in the illustration. A pit is first dug in the ground, and thickly lined with dry branches, straw, &c. The roof is constructed in the same manner, only the non-conducting power is increased by a thick coating of earth over the sticks and straw. The door, which is approached by a shelving cutting, is similarly protected, the covering only being removed when the door is opened.

I once made a very effective refrigerator out of two hampers, putting a small hamper inside a large one, and packing the space between them with straw.

In Nature we find many examples of this principle, which enables the inhabitants to bid defiance to frost.

A familiar example may be found in the cocoon of the common Silk-worm (Bombyx mori), and indeed in that of almost any silk-producing insect. When the caterpillar is about to make its cocoon, it begins by a number of rather strong threads attached to different points, and making a sort of scaffolding, so to speak, for the cocoon itself. Upon these is spun a slight outer cocoon of very loose and vague texture—the “floss silk” of commerce, and within that is the cocoon proper, in which the insect lies enclosed. It will be seen, therefore, that there are really three cocoons, one within the other, namely, the scaffold cocoon, the floss cocoon, and the silk cocoon itself, so that the inmate is protected from variations of temperature.

The cocoon of the emperor-moth, which has already been described, is made on the same principle.

There are several caterpillars which are social in their early stages, and which construct a common habitation. The Little Ermine-moth. (Hyponomeuta padella) affords a familiar example of this structure. The caterpillars are great roamers in search of food by day, and travel from branch to branch on their strong silken threads. At night, however, they return to a large white silken habitation which they have spun, and which they divide into many compartments, as may easily be seen by cutting the nest open with very sharp scissors. Within this habitation the caterpillars spin their separate cocoons, so that the system of double walls is thoroughly carried out.

There is another insect, very common on the Continent, but, happily for us, not introduced into England. It is called the Processionary Moth, from its curious habit of marching in exact lines, the head of the second caterpillar touching the tail of the first, and so on. These insects have likewise a common home, and spin their own separate cocoons within it.

There are two other sociable British Moths which make nests on a similar principle. These are the Gold-tailed Moth (Porthesia chrysorrhœa) and the Brown-tailed Moth (Porthesia auriflua). They are both beautifully white insects, but may easily be distinguished from each other, the Gold-tailed Moth having some brown-black spots on the upper wings, and a tuft of golden-yellow hairs at the end of the body; while the Brown-tailed Moth is without spots, and the tail-tuft is brown.

In habits they are very similar, and the description of the nest made by one will answer for that made by the other. I believe that broods of these two species have been known to construct a common nest. The nest is extremely variable in form, because it depends much on the number of twigs which it includes. Interiorly, it is divided into a considerable number of chambers, each containing one or several individuals.

As the caterpillars are hatched late in summer, they have to undergo the frosts of winter before they can attain their perfect state. Accordingly, before the winter-time comes on, they strengthen both the external walls and internal partitions of their nest, and then wait until the spring brings forth the leafage of the new year.

The nest is a beautiful structure, and I strongly recommend the reader to look for one in a hedgerow, take it home, and cut it up carefully. I would, however, advise him, if, like myself, he be subjected to a very sensitive skin, to be cautious in his handling of the nest. The hairs with which the pretty black, red, and white caterpillars are studded are irritant in the extreme.

I have several times suffered from them, and would much rather be severely stung by nettles than undergo the fierce irritation, mixed with dull heavy pain, which always accompanies the presence of these hairs. With me, as I suppose would be the case with persons of similar organization, these hairs cause large, hard tubercles to rise, just as if potatoes had been placed under the skin. The hairs of the Processionary Caterpillar have a similar effect, and in France the authorities have several times been obliged to close the public gardens for months, so severe was the pain which the caterpillars inflicted on persons who passed through the spots infested by them.

Mud Walls

There is a mode of wall-building which is much in vogue in some parts of England, and has much to commend itself. This is the Mud or Concrete Wall.

At first sight, the very name of a mud house gives an idea of poverty and misery, and is apt to be connected with hovels and pigsties. Mud walls, however, if properly built, are far warmer and drier than those of brick, and are even preferred to those of stone, when the latter can be easily and cheaply obtained. In Devonshire, for example, where even the cattle-sheds, or “linhays” (pronounced linny), and the pigsties are made of the rich red stone of the county, it is a common thing to see village houses built of mud. Sometimes the houses are built of stone to the height of some ten or twelve feet, and the upper parts made of mud.

If the builders are in any way fastidious, they make their walls of a uniform surface by placing two rows of planks on their edges at a distance from each other proportionate to the thickness of the wall, pouring the mud between them, and, when it has sufficiently hardened, shifting the planks. This, however, is not necessary, and detracts much from the picturesque look of a genuine mud wall, especially when it is of that rich red which characterizes the Devonshire soil. These mud walls are locally known by the name of Cob.

We have not to go very far in Nature to find good examples of the strength which can be attained by mud walls.

In all parts of the world where Termites, popularly but wrongly called White Ants, are to be found, the strength and endurance of the mud wall can easily be tested. Of gigantic dimensions when compared with the size of the architect, they not only endure the rain-torrents which wash over them, but can sustain the weight of the wild cattle, which are in the habit of using them as watch-towers, and this although they are hollow, and filled with chambers and galleries.

In Southern Africa these nests are much utilised. There is an animal called by the Dutch settlers the Aard-vark, which feeds almost wholly on Termites. At night it issues from its burrow, and, being armed with large and powerful claws, tears a great hole in the side, and devours the inmates.

These deserted nests are sometimes used as ovens, as we have already seen, a fire having been kindled within them for some time, the meat, well enveloped in leaves, being thrust into them, and the opening closed with clay. Sometimes they are used as graves, the corpse being placed in them, and the hollow filled up with earth, while the wall of the Termite nest, when pounded and mixed with water, is found to be the most tenacious clay that can be used for building or flooring huts.

Porches, Eaves, and Windows

We now come to some of the appendages of a house, namely, the Porch by which the rain is kept from a doorway, the Eaves by which it is kept from the walls, and the Windows which will admit light and air, but will prevent the entrance of intruders.

We first take the Porch, two examples of which are shown in the accompanying illustration, one being the work of human hands, and the other that of an insect.

The figure on the right hand represents an old-fashioned Porch, such as is often to be seen attached to old village churches, and which, being furnished with seats, serves also as a resting-place for those who are weary.

The figure on the left hand of the illustration is a wonderful example of the Porch, as constructed by insects. It is the nest of a honey-making Brazilian wasp named Myrapetra scutellaris. The peculiarity of this nest consists in its exterior being covered with a vast number of projections made of the same material as the walls of the nest, but more solid and much harder. The colour of the nest is blackish brown.

The object of all these projections has not been ascertained, but there is no difficulty as regards some of them. Without a very careful examination, it is exceedingly difficult to see any opening by which the inhabitants of the nest can go in and out. It will be found, however, that there are many entrances, which are set in a row round the nest, each opening being situated under a projection, which thus performs the office of a porch as well as that of concealment.

Another hymenopterous insect carries out the principle of the Porch in its nest. This is the Myrmica Kirbyi, a tiny reddish Ant which inhabits India. It makes its nest of cow-dung, which it works up into a texture very like that of an ordinary wasp-nest. A series of large flakes of this substance overhang the entrances, so that the inhabitants can enter freely, while rain is kept out. For the purpose of greater security, one very large flake covers the roof in umbrella fashion. The whole nest is globular, and about eight inches in diameter.

Next we come to the projecting Eaves, like those of our houses, and serving to preserve the body of the edifice itself from wet. On the right hand of the illustration there is an example of the eaves as they are still to be seen in some of our country places, where the less picturesque slates have not yet superseded the old thatch. In some places these eaves extend considerably beyond the walls, and I know of several instances, especially in North Devon, where a supplementary set of eaves extends, like a penthouse, throughout the length of the building, and just above the windows of the ground-floor.

The reader will remark that the projections upon the Myrapetra’s nest may very well fulfil the office of eaves as that of porches, and not only shelter the entrances, but serve to shoot the wet off the walls of the nest.

On the left hand of the illustration are several instances of eaves as existing in Nature.

In the centre is the compound nest of the Sociable Weaver-bird of Southern Africa (Philetœrus socius).

This is a dwelling constructed very much after the fashion adopted by many hymenopterous insects, namely, that each pair of birds make their own individual nest, but unite with their companions in constructing a common roof or covering. More than three hundred nests have been found in a single habitation, and sometimes the birds miscalculate, or rather, do not calculate the resisting power of the branches, and, when the rainy season comes, the additional weight of water brings down the whole edifice with a great crash.

The thatch which covers this congeries of nests is made of the Booschmannees-grass, whose long leaves and tough wiry stems are admirably adapted for throwing off water, even though they be not bound together like our more regularly constructed thatch.

Perhaps the reader may be aware that in the Orang-outan, the Chimpansee, and other large apes, the hairs of the arms are very long, and point in different directions, so that if the creature should be caught in a rain-storm, and, after the manner of its kind, fold its arms on its breast, with the hands resting on the shoulders, the rain is shot clear of its body, the hairs performing the duty of eaves.

Both Japan and China have a rain-cloak, constructed on exactly the same principle as the thatch of the Sociable Weaver-bird. They are nothing more than successive rows of long grass-blades fastened to a network of the proper shape. No amount of rain or snow can wet them through, and they have the advantage of being pervious to the exhalations of the body, though impervious to external moisture.

In this respect they are greatly superior to our waterproof coats, for, if the wearer has to undergo much bodily exertion, or is obliged to wear it for any length of time, he finds his clothing nearly if not quite as wet as if he had allowed the pure rain to fall on him from the clouds. I possess specimens of each kind of cloak.

When I procured them they were quite blackened with London smoke, and, on account of their resistance to water, washing them was a very long and troublesome business.

Above the nest are two patches of the Booschmannees-grass, as they appear when laid by the bird.

Below the nest is a group of the eggs of the Gold-tailed Moth, whose nest has already been described. Perhaps the reader wonders where the eggs are. Owing to the mode in which they are arranged, only a few can be seen, and are represented by the little white spots in the lower part of the figure. When the Gold-tailed Moth is ready for the great business of laying her eggs, she seeks a suitable place, and then piles them up in the form of a shallow cone. Her task, however, is not yet finished. Having arranged her eggs, she scrapes off the long downy hairs of the tail-tuft, and arranges them carefully on the eggs so as to cover them with a conical thatch, very much resembling that of an ordinary corn-rick.

The Brown-tailed Moth acts in a similar fashion.

Furs of various kinds act in the same manner, being impervious to wet during the life of the animal. Such, for example, is the fur of the Beaver, that of the Capybara, and that of the Seal, which are animals living in our time. These, however, are exceeded in their thatch-like powers by the three successive coatings of hair that were worn by the ancient Mammoth, the outermost being very long and very coarse, and hanging down in heavy tufts so as to shoot the water from them.

Being on the subject of roofs, we will take a few more examples of the roof as anticipated in Nature.

That parallel fibres, whether animal or vegetable, can throw off rain when properly arranged, has already been shown. Much more is it evident that flat or partly flat plates will have the same effect, if they be arranged so that the joints are “broken,” as masons and bricklayers say, i.e. so that the broad part of the upper row of plates overlaps the junction of two of the plates in the row immediately below it.

On the right hand of the accompanying illustration are given two sketches of a modern roof, one slated and the other tiled. The figures on the left show that this formation has been anticipated by Nature, in the wonderful system of scales which cover the wings of butterflies and moths, and to which all their brilliancy of colour is owing. In spite of their minute size, most being too small to be distinguished by the unaided eye, they are arranged as regularly as the best workman could lay the slates or tiles on a roof, and on exactly the same principle.

The shapes of these scales vary in almost every species, but they are always arranged on the same plan, namely, being placed in successive rows, each overlapping the other.

In consequence, it is almost impossible to wet a butterfly’s wing with water. The insect may be plunged beneath the surface, and the long hairs of the body will be soaked and cling together in a very miserable fashion. But the water rolls off the wings like rain off a slated roof, and even if a few drops remain on the surface, they can be shaken off, and the wing will be perfectly dry.

Mostly these scales are flat, but sometimes they are curved. I have among my microscopic objects a piece of wing from a South American butterfly, the scales of which are oblong and bent, just like the curved tiles shown in the second right-hand figure of the illustration. These beautiful scales are deep azure or warm brown, according to the direction of the light.

Perhaps my readers may call to mind that some architects dislike the flat, square form in which slates are usually put on roofs, and try to make them less formal.

Sometimes they take their square slates, and fit them with one of the angles uppermost, so that each slate looks something like the ace of diamonds in a pack of cards. Sometimes they are still more ambitious, and certainly succeed in producing a better effect, by cutting the slates in hexagons instead of squares, and fixing them as shown in the right-hand figure of the illustration. Putting aside the familiar hexagons of the honeycomb, and the apparent hexagons of an insect’s compound eye, we have in the common Tortoise an example of hexagonal plates that exactly resembles the slate roofing.

In the next illustration we have a variety of the same principle exhibited in differently shaped tiles and scales. The figures on the right hand show the pointed, the square, and the oblong tiles. These also would answer very well as representations of different forms of scale armour, the one being intended to throw off rain, and the other to repel weapons.

On the other side of the illustration are examples taken from the animal kingdom. First comes the Bajjerkeit, or Short-tailed Manis, which has already been mentioned, and whose imbricated scales will resist the blows of any spear or sword. As to my own specimen, when it is struck, it resounds as if it were a solid plate of metal, and I should think that during the lifetime of the animal a reasonably strong axe would not easily make its way through that coat of mail.

Below the Manis are a pair of fish, whose scales, though not so strong as those of the mammal, yet are arranged in the same manner, and answer the same purpose. The last figure represents three scale-bands of the Armadillo, an animal which has already been mentioned. I may as well state here that in several anthropological museums there are various portions of defensive armour made from the scale-clad skin of the Crocodile, Manis, and similar animals.