INTRODUCTION.
If we are struck with wonder and admiration at the progress of the arts and manufactures, and have daily reason to congratulate ourselves on the skill and ingenuity of our fellow-creatures, by which our comforts and conveniences are so much increased; it must also occasionally have crossed our minds, that some of the meaner creatures, though not gifted with our reasoning powers, and therefore not able to profit by the experience of the past, are yet employed in their several departments, and according to their several wants, in exceedingly curious and useful manufactures, mostly designed for the shelter and preservation of themselves or their offspring, but serving, not unfrequently, a higher purpose, in administering to the wants of mankind.
In reading the history, or in watching the proceedings of birds and insects, how many remarkable instances do we meet with of that which may be called manufacture, though performed without hands! How curious to watch in the early spring the proceedings of those busy basket-making birds, the rooks! Rude and clumsy as their nests may at first appear, it is just the sort of workmanship best calculated for their wants. They do not, indeed, choose the smooth and flexible osier-twigs which we should think necessary for basket-making, but they contrive by means of brittle, dead, forked sticks, to plait together a strong bristling out-work, within which they interweave a finer basket-work of fibrous roots, rude indeed, but not inelegant or unsuitable. Then, among birds and insects too, what persevering and industrious carpenters, masons, tailors, miners, and weavers may we not find. Perhaps there are not many persons who have watched the mason-wasps boring their galleries in brick or sand, or building the round towers which serve them as out-works; nor the mason-bee, as she plasters together her neat mud-wall cottage or cell, as the future habitation of her young; but there are few persons unacquainted with the masonry of the chimney swallow, or of the house-martin twittering on the eaves. With no other tools than those which nature supplies, how cleverly do these creatures shape and mould their nests into the required form, using for their work a mortar carefully prepared by their own labour and skill, and just of the consistency required. Few, again, may have had an opportunity of seeing carpenter-bees boring holes in posts or palings, and forming their smoothly chiselled cells, or of inspecting the partitioned galleries dug out in old timber by carpenter-wasps; but perhaps many persons have observed the colonies of emmets, or carpenter-ants, working in the trunks of decaying oak or willow trees; or they may have listened to that interesting carpenter-bird, the wood-pecker, tapping and boring into trees, in pursuit of insects, and for the purpose of making a nesting-place for its young. Most of us know only by hearsay that there are tailor-birds, common enough in American orchards, who sew together broad pieces of grass to make their nests, working them through and through, as if actually done with a needle; but almost every one can say from his own knowledge, that there are weaver-birds, such as our common hedge-sparrow and chaffinch, who weave a circular piece of haircloth for the interior of their nests, each hair being collected and interwoven singly, and always bent so as to lie smoothly in the hollow of the nest. Then who shall describe all the wondrous proceedings of tent-making caterpillars, upholsterer-bees, turret-building ants, net-making spiders, paper and card-making wasps, and spinning worms? Volumes have been written, and volumes might still be written on the history of these creatures. Any one possessing a garden, and taking delight therein, has ample opportunity of watching the habits of birds and insects, and of confirming, if not of adding to, the accounts given by naturalists, of the commoner species. But we must still be indebted to the patient observations of those who have made insects or birds their especial study, for many of the most curious particulars, and for all our knowledge of rare or foreign species.
Interesting as is the whole subject of bird and insect manufactures, there is one department in which we are more concerned than the rest; namely, that in which the product can be applied to our own use, either in the way of food or clothing. Now this department is supplied wholly by insects, no bird, that we are aware of, producing by its own manufacturing powers, any substance that can be so employed, unless, indeed, we except the curious edible nests of the Java swallow, which have been converted by the taste of oriental epicures into an article of food.
Let us then proceed to notice such of the insect manufactures as are useful to man, and trace, at the same time, the history and performances of these small but not insignificant manufacturers.
CHAPTER I.
MANUFACTURE OF SILK BY CATERPILLARS OF VARIOUS KINDS.
The most important of all the insect manufactures is doubtless that of silk-spinning. It seems almost past belief that the magnificent velvets, satins, and silks which form so elegant a part of female attire, and which are heaped together in such costly profusion in the shops of the metropolis, and in those of all considerable towns, whether in our own, or in foreign countries—that these splendid fabrics, together with all ribbons, gauzes, damasks, or other articles composed of silk, should owe the raw material of which they are formed to the labours of a race of little creeping caterpillars, which in this their early and imperfect state spin for themselves cocoons, or cases of silk, where they may quietly undergo their changes until they become perfect winged insects.
CATERPILLAR SUSPENDED BY ITS SILKEN THREAD.
The astonishing task of supplying silk for the whole civilized world is performed almost without exception by the common silkworm, or caterpillar of the mulberry-tree moth. But it must not be supposed that this is the only silk-producing insect. On the contrary, all the caterpillars of butterflies and moths have the power of spinning a certain quantity of silken thread, however small, and however inferior to that of the silkworm, properly so called. It is very common in gardens to see numbers of caterpillars dangling by their silken threads from the young branches of fruit-trees. In this way they let themselves down, or break their fall if blown off by the wind, or otherwise shaken from their favourite tree. And in the case of some caterpillars when the insect has completed the term of its existence and becomes a chrysalis, it suspends itself by silken cords to some fixed point, where it remains in complete repose, without food, perhaps for months before the perfect winged insect bursts forth, as different a creature from the caterpillar as the chrysalis is from either,—and yet these are but three different states of existence of the same insect.
CHRYSALIS SUSPENDED BY SILKEN CORDS.
According to the particular species of caterpillar, the silk will vary in strength and fineness, and also in colour, but seldom will it be found strong enough, or in sufficient quantity to be of use to us. The insects themselves employ it in many ways for their own safety and shelter. How common it is to find some of the leaves of a lilac-tree made up into little rolls, or folded together at their edges, where they stick so fast that it requires some little force to pull them asunder. This is the work of a small caterpillar, whose subsistence is found on that tree. A single egg has been laid on each leaf selected by the parent moth, and soon after it is hatched, the caterpillar begins rolling up the lilac leaf, and fastening the edges with silk. This is a work of time, but gradually proceeds as the caterpillar increases in strength, until at last it is shut up in a gallery of its own making, safe from the attacks of birds and larger insects. The leaves of various other trees are rolled in a somewhat similar manner, as those of the oak, the willow, and the rose, and also those of humbler plants, as the plantain, nettle, thistle, &c. The mode in which these leaf-rolling caterpillars set to work to form convenient habitations of the leaves of the plants on which they feed, is well described by Kirby and Spence.
OAK LEAF ROLLED BY A CATERPILLAR.
“Some of these merely connect together with a few silken threads several leaves, so as to form an irregular packet, in the centre of which the little hermit lives. Others confine themselves to a single leaf, of which they simply fold one part over the other. A third description form and inhabit a sort of roll, by some species made cylindrical, by others conical, resembling the papers in which grocers put their sugar, and as accurately constructed; only there is an opening left at the smaller extremity for the egress of the insect in case of need. If you were to see one of these rolls, you would immediately ask by what mechanism it could possibly be made—how an insect, without fingers, could contrive to bend a leaf into a roll, and to keep it in that form until fastened with the silk which holds it together? The following is the operation: the little caterpillar first fixes a series of silken cables from one side of the leaf to the other: she next pulls at these cables with her feet; and when she has forced the sides to approach, she fastens them together with stronger threads of silk. If the insect finds that one of the larger nerves of the leaf is so strong as to resist her efforts, she weakens it by gnawing it here and there half through. What engineer could act more sagaciously? To form one of the conical or horn-shaped rolls, which are not composed of a whole leaf, but of a long triangular portion cut out of the edge, some other manœuvres are requisite. Placing herself upon the leaf, the caterpillar cuts out with her jaws the piece which is to compose her roll. She does not, however, entirely detach it; it would then want a base. She detaches that part only which is to form the contour of the horn. This portion is a triangular strap, which she rolls as she cuts. When the body of the horn is finished, as it is intended to be fixed upon the leaf in nearly an upright position, it is necessary to elevate it. To effect this, she proceeds as we should with an inclined obelisk. She attaches threads, or little cables, towards the point of the pyramid, and raises it by the weight of her body.”
Other larvæ form their habitations wholly of silk: one that inhabits the leaves of pear-trees forms a little tent; another a sort of cloak; another, as in the case of the silkworm, a complete ball of silk.
PENDULOUS NESTS OF CATERPILLARS.
Among leaf-rolling caterpillars, one of the most curious is described by Bonnet, in which the nest hangs suspended from the branch of a fruit-tree by a strong silken thread. It is formed of one or two leaves neatly folded and fastened together with silk, and in this small enclosure several caterpillars live harmoniously together.
LEAF CUTTING CATERPILLAR.
There is also a very curious and beautiful nest formed by a rare insect, which has only yet been observed in its caterpillar state; but its proceedings therein are interesting and highly remarkable. The length of the body in this caterpillar varies from six to eight inches, the thickness is half a line. The general colour is bluish green, tending to yellow about the head; the feet are black, and six in number. At the extremity of the body are two points projecting sideways. The eyes are visible and prominent in this caterpillar, and besides the antennæ there are two or three pairs of palpi or feelers, which perform the office of hands. This insect inhabits the nut-tree, and cuts out from its leaves a most ingenious case, which serves for its dwelling-place. This case is of a singular form, being an elongated cone, very narrow at the extremity, and tolerably wide at the orifice. It is formed of a strip of nut-leaf, wound up in a spiral manner, but so cleverly contrived that the strip is very narrow at the extremity, and gradually widens as the work proceeds. This happens from the gradual progress of the work, which is begun in the early stage of the caterpillar’s existence, when it does not require a large dwelling-place, and becomes more and more extended to suit the growth of its inmate. When it is completed, it is rather more than an inch long, and two lines in diameter at the orifice. The outside of the case presents the upper surface of the leaf in which the indentations are preserved. The dwelling is a spacious one for the caterpillar, so that it can turn round in it with perfect ease. The band of which the cone is composed is taken from the edge of the leaf, which the caterpillar cuts away in proportion as it winds it round its own body. When one portion has taken the required form, a little more is cut out, but always in a direction parallel with the edge of the leaf. While the insect is thus gradually rolling itself up in a case, it also feeds vigorously on the leaf, taking care, however, always to spare the band which forms its habitation. Another part of the cleverness of this insect consists in maintaining this strip of leaf in its spiral form, which would otherwise naturally unwind by its own weight, and flutter in the wind as a torn fragment. Here it is that silk is again skilfully employed. The caterpillar commences much as other leaf-rolling insects do, by fastening a thread to the edge of the leaf and drawing it towards the desired point. But as the work proceeds the insect generally has three skeins or bands of silk extended from the opening of its case to the leaf. The first is the shortest and the most direct, issuing from the interior of the roll; the second is fastened to the middle of the last spiral, and extends to the leaf; the third is more extensive still, and all three are admirably disposed for keeping the leaf bent to the proper form. These skeins are composed of a great number of threads parallel with each other, which not only serve to retain the leaf in its spiral form, but also serve the caterpillar as a kind of ladder, by which it mounts, and on which it rests while cutting out fresh portions of leaf.
LEAF-NEST UNWOUND.
It sometimes happens accidentally to this caterpillar that the case becomes detached from the leaf, or naturalists have purposely severed a portion to see what would be the result; but this does not greatly disturb the insect, for as long as a single thread of silk remains to hold the pieces together, the caterpillar is able to repair the evil. It will unite the fractured portion almost imperceptibly by means of silken threads, and proceed with its case as before; but if the leaf dry up and wither, the insect is then compelled to desert it, and to select a younger and fresher leaf for its operations.
What is still more curious, on the completion of the dwelling, the caterpillar sometimes wishes to make an excursion to another part of the leaf, and to take its house with it, and this it accomplishes in the following manner. Coming more than three parts out of the cone, the creature makes new skeins in advance of the old, and attempts to pull the cone forward by their means; but finding that this does not succeed, it bends its body back, and quickly severs the old threads and the portion of leaf which keeps the case immovable. It is now able to draw the case onwards a certain distance, after which it has only to repeat the operation, and make other new skeins in advance of these, to continue its onward journey. Thus it arrives at the opposite edge of the leaf, where it carefully adjusts its case to the under side, fastening it with great ingenuity, and drawing the threads tighter where the cone is not properly balanced. In all these cases, silk is the useful material by which the caterpillar secures its nest, and provides for its own safety: it is also a constant resource in case of danger, or of accident, as the following anecdote will show. A caterpillar of the goat-moth, being confined in a smooth glass sugar-basin, managed to crawl up the slippery sides and escape. This excited great surprise in the naturalist (Rösel) who had imprisoned the creature, and he therefore took occasion closely to watch its proceedings when again placed in a similar vessel. It was with surprise and admiration that he now saw the caterpillar constructing a silken ladder on the side of the glass; the natural gum of the silk being sufficient to secure it even to that perfectly smooth surface. Up this ladder the creature crawled, and thus easily and expeditiously made its escape.
SILKEN LADDER SPUN BY THE GOAT-MOTH CATERPILLAR.
Silkworms abound in our own country, as well as in others; but the silk they spin is too fragile and scanty to be employed for other purposes than their own. It is different with some of the caterpillars of India. Although the great supply of silk is there obtained, as with us, from the silkworm of the mulberry-tree, yet the caterpillars of various moths also furnish a considerable quantity. The most important of these are the Tusseh and Arindy silkworms, both natives of Bengal. The first feeds on the leaves of the jujube tree and of the asseen, and is found in such abundance as from time immemorial to have afforded a constant supply of coarse, dark-coloured silk, which is woven into a cheap but very durable cloth.
THE TUSSEH SILKWORM.
When the caterpillars approach their full size they are too heavy to crawl in search of their food with the back upwards, as is usual with most caterpillars, but traverse the small branches suspended by the feet, as is shown in the figure.
COCOON OF THE TUSSEH SILKWORM.
When the caterpillar is ready to spin its cocoon, it connects by means of the silk, (which is always glutinous when newly spun,) two or three new leaves into an outer envelope, which serves as a basis to spin the complete cocoon in, besides the cocoon being suspended from a branch of the tree in a wonderful manner, by a thick, strong, consolidated cord, spun of the same material by this persevering creature.
The cocoon is of an exact oval shape, and very firm in texture: in it the animal remains dormant, and perfectly protected, for about nine months, namely from October until July; so that it makes its appearance in time for the caterpillars to come into existence, when Providence has furnished them with the greatest plenty of proper food. When the insect is prepared to make its escape and be changed into its perfect state, it discharges from its mouth a large quantity of liquid, with which the upper end of the case is so perfectly softened as to enable the moth to work its way out in a very short time; an operation which is always performed during the night. In their perfect state these insects do not exist many days: the female deposits her eggs in the branches of the tree she may be resting on, to which they adhere firmly by means of the gluten they are covered with when newly laid.
The eggs are white, round, and compressed, with a depression in the centre on each side. They hatch in from two to four weeks, according to the state of the weather. The larvæ or caterpillars acquire their full size, which is about four inches in length, and three in circumference, in about six weeks: they are nearly the colour of the leaves they feed on, with a light yellowish stripe on each side; under these stripes the middle segments are marked with an oblong gold-coloured speck. The back is also marked with a few round darker coloured spots, from which issue a few long, coarse, distinct hairs, while others of smaller size are scattered over the insect.
The Tusseh silkworm is found in such abundance over many parts of Bengal and the adjoining provinces, as to afford to the natives a large supply of the durable, coarse, dark-coloured silk, already mentioned, commonly called Tusseh silk, which is woven into a kind of cloth called Tusseh doot’hies, much worn by Brahmins and other sects of Hindoos. This substance would no doubt be highly useful to the inhabitants of many parts of America and the south of Europe, where a cheap, light, cool, durable dress, such as this silk makes, is much wanted. Millions of cocoons of the Tusseh silkworm are annually collected in the jungle, and brought to the silk factories near Calcutta. In other parts the people gather and transplant them to the trees near their own dwellings, that they may watch over the safety of the caterpillars, which are very liable to be devoured by crows during the day time, and by bats at night.
The Arindy silkworm feeds only on the leaves of the Palmi Christi; it produces so delicate and flossy a silk that it cannot be wound from the cocoons; it is therefore spun like cotton, and the thread woven into a coarse kind of white cloth, of a loose texture, but so durable that a person can scarcely in his lifetime wear out a garment made of it.
Eleven different species of silkworm have been enumerated as natives of India, which has thus the internal means of providing the whole of Europe with a material which would rival cotton and woollen cloth, and would often be preferred to both, could it be obtained at a low price. The produce of the Arindy silkworm, when sent to this country was much admired, and some manufacturers to whom it was shown seemed to think that they had been hitherto deceived in the account of the shawls of India being made from the wool of a goat, and that this silk, if sent home, could be made into shawls equal to any manufactured in India.
Many of the larvæ of the European moths afford a very strong silk, and it is said, that a manufacture of silk from the cocoons of the emperor moth was at one time established in Germany. There is no doubt, however, that silk might be collected in abundance from many native silkworms in America. Cocoons have been described eight inches long, made of grey silk, which the inhabitants of Chilpancingo, Tixtala, and other places in South America, manufacture into stockings and handkerchiefs. Humboldt also observed similar nests in the provinces of Mechoacan, and the mountains of Santa Rosa; they were of dense tissue, resembling Chinese paper, of a brilliant whiteness, and formed of distinct and separate layers. The interior layers, which are the thinnest, and of extraordinary transparency, were used by the ancient Mexicans as writing tablets.
CHAPTER II.
MANUFACTURE OF SILK BY THE SILKWORM.
We now come to the most important of all silk-spinning insects, the common silkworm, or caterpillar of the mulberry-tree moth. The labours of this insect were known and appreciated in other parts of the world long before we had tidings of its existence; so that the peasantry of other lands were clad in raiment which our kings would have been proud to wear. “When silk was so scarce in this country that James the First, while King of Scotland, was forced to beg of the Earl of Mar the loan of a pair of silk stockings to appear in before the English ambassador, enforcing his request with the cogent appeal, ‘for ye would not, sure, that your king should appear as a scrub before strangers;’ nay, long before this period, even prior to the time that silk was valued at its weight in gold at Rome, and the Emperor Aurelian refused his empress a robe of silk because of its dearness, the Chinese peasantry in some of the provinces, millions in number, were clothed with this material; and for some thousand years to the present time, it has been both there and in India (where a class whose occupation was to attend silkworms appears to have existed from time immemorial, being mentioned in the oldest Sanscrit books,) one of the chief objects of cultivation and manufacture. You will admit, therefore, that when nature
——Set to work millions of spinning worms,
That in their green shops weave the smooth-haired silk
To deck her sons,
she was conferring upon them a benefit scarcely inferior to that consequent upon the gift of wool to the fleecy race, or a fibrous rind to the flax or hemp plants; and that mankind is not under much less obligation to Pamphila, who, according to Aristotle, was the discoverer of the art of unwinding and weaving silk, than to the inventors of the spinning of those products.”
EGGS AND SILKWORMS IN THE FIRST AGE.
It is so common an amusement with young persons in this country to procure the eggs of silkworms, rear the insects, and watch their changes that numbers are acquainted with the growth, habits, and manner of spinning of these interesting creatures. Perhaps a sheet of paper is given to a little boy or girl, on which are a number of small specks, no bigger than pins’ heads: these specks, the child is told, are silkworms’ eggs, and if he keeps them dry during winter, and then places them in a sunny window in spring, he will get a number of caterpillars from them. Taking care to do this, the child is delighted some fine morning to see a few little dark coloured worms crawling about the paper, while others are just issuing from the eggs. Perhaps a difficulty now arises about their food. In warm countries the leaves of the mulberry-tree are ready for the insects as soon as they are hatched; but in England, unless the eggs are purposely kept back, by putting them in a cold place, the caterpillars come out before the mulberry-tree has put forth its leaves. A few tender leaves of the lettuce are therefore spread lightly over the young caterpillars, and upon these they mount, and at last begin to feed, after searching in vain for their natural food. But the worms do not thrive on this diet, and it is much better so to manage the eggs that they may be hatched when the young leaves of the mulberry are just opening. These form the best possible food in that tender state, and in order to economise it, the leaves should be cut in small pieces; because the caterpillars feed only on the edges, and thus great part of a leaf, when given to them whole, is entirely wasted.
THE WHITE MULBERRY.
(Morus alba.)
In Italy, where great attention is paid to the cultivation of the silkworm, the eggs are hatched in a room heated by a stove, and the young caterpillars are then removed on their mulberry-leaves to a cooler apartment called the nursery, where they are managed with great care and skill. Wicker shelves are arranged in the room at convenient distances, and are lined with paper, on which the worms are placed. Care is taken to place together only such worms as are hatched at the same time, for without this precaution the treatment, with respect to food, could not be regulated, and the moultings would not take place at the same time. Great care is also taken to secure the worms from rats and mice, as well as from certain insect enemies.
Silkworms are so little disposed to wander away from their food that open trays are sufficient to secure them: but unless great cleanliness is observed in their management, and frequent change of food given, a sickly smell is observed, and the caterpillars languish and die in great numbers. Supposing the young brood goes on well, and is properly attended by the child whom we have supposed to undertake the charge, there will be about five or six days’ feeding, and then the worms will begin to sicken for their first moult, or casting the skin. Silkworms have four of these moults, at each of which they appear to suffer pain or inconvenience; they also entirely leave off eating for two or three days. The caterpillars at that time raise the fore part of their bodies, and show tokens of uneasiness. They have grown rapidly, and their skins, not having grown in proportion, now appear to press and inconvenience them; but after two or three days fasting, they become thinner and are able gradually to rid themselves of their skin. It is now that their owner may see the use they begin to make of their silk. By watching them closely he sees each caterpillar throw out a number of very fine silken lines, by which it fastens the skin to one spot. Having done this, it is able to creep out, without dragging the skin about after it, as would otherwise be the case. In this operation the whole covering of the body, including that of the feet, of the jaws and teeth, is cast off; but it sometimes happens that the animal cannot entirely cast its skin, a portion of it breaking and remaining attached to the extremity of the body. As the animal increases rapidly in size, this portion of the old skin compresses its body tightly, causing inflammation and much suffering, which usually ends in death.
Worms that have newly moulted are readily distinguished by their pale colour, and the wrinkled appearance of the new skin. Soon after moulting they recover health and vigour, and feed with increased appetite. To keep them in health they must be fed with great regularity, and not crowded together in their trays. In the course of five days the rapid growth of the insect causes the wrinkles to disappear from the skin; it is now half an inch in length; a second sickness, and a second moulting, prepare it for increase of growth; it casts its skin as before, and feeds without intermission during another five days, during which time it attains a length of three quarters of an inch. It then falls sick and moults a third time. It again feeds during five days, after which it casts its skin for the fourth and last time in the caterpillar state.
PROGRESSIVE GROWTH OF THE SILKWORM.
It is now about one and a half or two inches in length, and devours its food most voraciously, increasing rapidly in size during ten days. When the worms are fed a slight hissing noise is heard similar to that of green wood burning. According to some writers this noise proceeds from the action of the jaws, but others attribute it solely to the action of the feet, which are continually moving until the worms have fastened to their food, when the noise ceases. In a large nursery of silkworms this noise sounds like a soft shower of rain.
SILKWORM ON MULBERRY-LEAF.
When the caterpillar has attained its full growth, it is a very different creature from the little black worm which first issued from the egg, being from two and a half to three inches in length, and its body consisting of twelve membranous rings, which contract and elongate as the animal moves. It is furnished with sixteen legs, in pairs: three pairs in front, under the first three rings, are covered with a shelly or scaly substance; the other five pairs, called holders, are furnished with little hooks, which assist the insect in climbing. The head is covered with a scaly substance similar to the covering of the fore legs. The mandibles are of great strength, and indented like the teeth of a saw. Beneath the jaw are two small openings, through which the insect draws its silken lines. The substance of which the silk is composed is a fine yellow transparent gum, secreted in two slender vessels, “which are wound, as it were, on two spindles in the stomach; if unfolded, these vessels would be about ten inches in length.” The insect breathes by means of eighteen holes or spiracles, distributed along the body, nine on each side. On each side of the head, near the mouth, are seven small eyes; the two specks higher up on the head, which are generally mistaken for eyes, are only parts of the skull.
FULL GROWN SILKWORM.
When the silkworm is ready to spin, it gets upon the leaves without eating them, rears its head as if in search of something, or crawls to the edges of the tray and moves slowly along; its rings draw in, and its greenish colour changes to a deep golden hue; its skin becomes wrinkled about the neck, and its body feels like soft dough, and on taking it in the hand, and looking through it, the whole body has assumed the transparency of a ripe yellow plum. When this is observed, the owner of the insects puts each singly into a little cone of white paper, which he pins to the wall or elsewhere, so that the creature may be undisturbed at its work. But in the nurseries abroad little bushes are set up on the wicker shelves, and the insects mount them and form their cocoons among the twigs.
Supposing the worm to be left to itself on the tray, without either of these precautions, it at last selects some corner or hollow place which will conveniently hold the cocoon it is about to spin, and begins by throwing out a number of irregular threads, which are intended to support its nest. Upon these it forms, during the first day, a loose structure of floss silk of an oval shape, within which, during the next three days, it winds the firm, hard, yellow ball, remaining, of course, all the time within it. In this operation the insect does not greatly change the position of the hinder part of its body, but continues drawing its thread from various points and attaching it to others, so that after a time the body becomes to a great extent enclosed by the thread. “The work is then continued from one thread to another, the silkworm moving its head and spinning in a zigzag way, bending the fore part of the body back to spin in all directions within reach, and shifting the body only to cover with silk the part which was beneath it. As the silkworm spins its web by thus bending the fore part of the body back, and moves the hinder part of the body in such a way only as to enable it to reach the farther back with the fore part, it follows that it encloses itself in a cocoon much shorter than its own body, for soon after the beginning the whole is continued with the body in a bent position. From the foregoing account it appears that with the most simple instinctive principles all the ends necessary are gained. If the silkworm shifted its position much at the beginning of the work, it could never enclose itself in a cocoon; but by its mode of proceeding, as above explained, it encloses itself in a cocoon which only consumes as much silk as is necessary to hold the chrysalis.”
THE COCOON.
(A portion of the floss silk has been removed.)
The use of the cocoon, in the natural state of the insect, is to afford a warm nest, where, secure from the inclemencies of the season, and the attacks of enemies, it may undergo its final changes. The cocoon is made water-tight by an internal lining of gum, and the silken thread of which the ball is made is also smeared with a similar gum, which hardens in the air.
THE CHRYSALIS.
GIRL WINDING SILK.
While the worm is spinning its cocoon it takes no food, and as it is continually emitting silk, its body gradually diminishes to less than half its original length. When its labour is completed it rests awhile, and then once more throws off its skin; but it is no longer a caterpillar; its form is changed into a chrysalis, or aurelia, with a smooth brown skin, and pointed at one end. A few days after the insect has finished spinning, the cocoons will be ready to be unwound. Our amateur silkworm cultivator then takes the cocoons out of the paper cones and separates the outer floss silk. He then throws several cocoons into a glass of water slightly warm, to make them more easy to unwind, and having found the ends, proceeds to wind the silk on a reel, or he gives the task to a sister’s gentler hands, while he prepares a little box of bran, in readiness to put the poor exposed chrysalis the moment it is released from the cocoon. As the winding proceeds, the cocoons become thinner and thinner until the insects within are visible. The chrysalis, though covered with a horny skin, and apparently without much sensation, shows very plainly that it is sensible of the rough treatment it is receiving, as the cocoon is tossed about in the water by the motion of the reel. It rapidly moves the rings of its tail, which is doubtless a sign of uneasiness or pain. When nearly all the silk is wound off, there still remains a transparent film like silver paper, which is torn open to let out the chrysalis. The latter is immediately buried in bran, where it remains very quietly for a week or two, then changes into a cream coloured moth, lays its eggs, and dies. This is the common domestic treatment when silkworms are kept for amusement, but in a commercial establishment such as those of Italy, they are very differently treated.
FEMALE SILKWORM MOTH AND EGGS.
The cocoons are collected in large quantities, separated and sorted according to their quality, about one-sixtieth part being saved for the production of eggs, after which the life of the chrysalis is destroyed in all the rest. This is done in hot countries by exposure to the sun; but in more temperate climes by artificial heat, such as that of an oven after the bread has been withdrawn. Before the cocoons can be reeled they must be separated from the floss, which is done by opening the floss covering at one end and pushing out the cocoon. Care is taken in reeling to use cocoons of one quality, as different qualities require a different treatment.
The natural gum of the cocoons is first softened in warm water, kept at the proper temperature, either by a charcoal fire or by a steam pipe. After remaining in this for a few minutes, the reeler (generally a woman) gently stirs up or brushes the cocoons with a short birch rod, and to this the loose threads of the cocoons adhere, and are thus drawn out of the water: they are then taken commonly four or five together, twisted with the fingers into one thread, and passed through a metal loop, to get rid of dirt and impurities: the thread then passes on to the reel, which is so constructed as to have a slight lateral motion, so that the thread of one revolution does not overlay the other; for if it did so, the threads would be glued together before the gum had had time to harden by exposure to the air. The threads of the four or five cocoons are thus united into one strong and smooth thread. Sometimes as many as thirty cocoons are united into one thread, and it is difficult to wind more. As often as a thread of any single cocoon breaks or comes to an end, the attendant supplies its place by a new one, so that by continually keeping up the same number the united thread may be wound to any length: these joinings are not made by a knot, but the new end is simply laid on the compound thread, to which it adheres by its gum; and as the threads are finer near their termination than at the commencement, it is necessary for the reeler to add other cocoons before the first set is quite exhausted; so that the compound thread may be of uniform thickness. The filaments of three fresh cocoons, added to two half-wound ones, make a thread about equal to that from four fresh cocoons. The cocoons are not entirely wound off, but the husk containing the chrysalis is used together with the floss silk under the name of waste. Improved methods of reeling have been introduced on the continent, but they are similar in principle to the above.
Eleven or twelve pounds of cocoons yield about one pound of reeled silk; and as from 240 to 250 cocoons weigh a pound, the number of cocoons required to produce a pound of silk may be estimated at 2,817½. The length of filament yielded by a single cocoon is 300 yards, but some have yielded as much as 625 yards.
The reeled silk is made up into hanks for sale or use. The form and contents, as well as quality, of these hanks, differ greatly, as will be seen by the following wood-cuts.
HANKS FROM ITALY.
BOOK OF SILK FROM CHINA.
SLIP FROM BENGAL.
We may aptly conclude our account of this most industrious silk-manufacturer in the words of the Rev. Samuel Pullein, M.A., who, so long ago as 1758, wrote an Essay on the Culture of Silk, in which the following passage occurs:—
“There is scarce anything among the various wonders which the animal creation affords more admirable than the variety of changes which the silkworm undergoes; but the curious texture of that silken covering with which it surrounds itself when it becomes a moth, and arrives at the perfection of its animal life, vastly surpasses what is made by other animals of this class. All the caterpillar kind do indeed undergo changes like those of the silkworm, and the beauty of many of them in their butterfly state greatly exceeds it; but the covering which they put on before this change into a fly is poor and mean, when compared to that golden tissue in which the silkworm wraps itself. They indeed come forth in variety of colours, their wings bedropped with gold and scarlet, yet are they but the beings of a summer’s day; both their life and beauty quickly vanish, and they leave no remembrance after them; but the silkworm leaves behind it such beautiful, such beneficial monuments, as at once record both the wisdom of their Creator, and His bounty to man.”
On the importance of the silk itself, Kirby and Spence have the following remarks:—
“To estimate justly the importance of this article, it is not sufficient to view it as an appendage of luxury unrivalled for richness, lustre, and beauty, and without which courts would lose half their splendour; we must consider it what it actually is, as the staple article of cultivation in many large provinces in the south of Europe, amongst the inhabitants of which the prospect of a deficient crop causes as great alarm as a scanty harvest of grain with us; and, after giving employment to tens of thousands in its first production and transportation, as furnishing subsistence to hundreds of thousands more in its final manufacture, and thus becoming one of the most important wheels that give circulation to national wealth.”
CHAPTER III.
MANUFACTURE OF SILK BY SPIDERS.
Our history of the silk manufacture among insects would be incomplete without a notice of the labours of spiders. Not only do these insects produce filmy webs to entrap their prey, but they also spin, for the protection of their eggs, a bag not much unlike the cocoon of the silkworm. At the beginning of the last century a method was discovered of procuring silk from these spiders’ bags, and of making it into several useful articles. The experiments took place in France, and it was there discovered that two species of spider in particular produced strong and beautiful silk, capable of being usefully employed. The structure of these insects was closely examined by the celebrated naturalist Réaumur, and he found that the silk is spun from five papillæ, or small nipples, placed in the hinder part of the body; these serve the purpose of so many wire-drawing irons, to mould a gummy liquor, which dries as it is drawn out and exposed to the air.
SPINNING APPARATUS OF THE SPIDER.
(Greatly magnified.)
On pressing the body of a spider, the liquor flows into these nipples, by applying the finger against which, distinct threads may be drawn out through the numerous openings; and, what is very astonishing, every separate thread is made up of innumerable smaller threads, so that Réaumur thought himself far within the limits of the truth when he stated that each of the five nipples supplied one thousand separate fibres, in which case the slender filament of the spider’s nest must be made up of five thousand fibres. By applying the whole, or a part, of this apparatus to her work, the spider can make the thread stout or fine at pleasure: thus the webs for entrapping flies are very slight and fragile; but the nest for securing the eggs is much stronger, to afford them shelter from the cold. The threads are wound loosely round the eggs in a shape similar to that of the silkworm’s cocoon. The colour of the silk is generally grey, becoming blackish on exposure to the air: sometimes it is pale yellow, and also of very fine quality; but this is the production of comparatively rare species, which could not be depended on for the purposes of manufacture. A spider’s nest preserved by the writer during the last winter was of a beautiful yellow, almost approaching that of the cocoon of the silkworm. As spring approached it increased in bulk and became rather paler, until at last a dark appearance in the centre betokened the bursting of the eggs. At the present time (April 10th) ninety-six small yellow-bodied spiders have come forth, and are actively engaged in weaving their delicate webs across the glass which contains them. A muslin cover admits air to the interior, and these minute insects appear perfectly healthy although deprived of their natural food. Some sugar was placed in the glass, but they do not appear to have consumed any of it, although some of them have been hatched for more than a fortnight. From the appearance of the nest, more of these spiders yet remain to be hatched.
In the French experiments, spiders’ nests in large quantities were collected from the trunks of trees, corners of windows and vaults, and eaves of houses at the time above mentioned, and from these a new kind of silk was obtained by M. Bon, who declared it to be in no respect inferior to that of the silkworm. It was afterwards proved that he was greatly mistaken in this respect; yet the spiders’ silk readily took all kinds of dyes, and was actually wrought into stockings and gloves, specimens of which were presented by M. Bon to the Royal Academy of Paris, and also to the Royal Society of London. His method of preparing the silk was as follows:—
Twelve or thirteen ounces of the bags were beaten with the hand, or by a stick, until they were entirely free from dust. They were then washed in warm water, which was frequently changed, until it was no longer discoloured by the bags. They were next steeped in a large quantity of water, wherein soap, saltpetre, and gum-arabic had been dissolved. The whole was then set to boil over a gentle fire for three hours. Lastly, the bags were rinsed in clear warm water, and set out to dry. They were then fit for the operation of carding, which was performed with very fine cards, and thus silk of a peculiar ash colour was obtained, which was spun without difficulty.
SPIDER’S NEST ATTACHED TO A FLAT SURFACE.
SPIDER’S NEST LAID OPEN.
The great obstacle which prevented the establishment of any considerable manufacture from these spiders’ bags, was the difficulty of obtaining them in sufficient abundance; but M. Bon, who was enthusiastic respecting the value of his discovery, fancied that he could easily overcome this obstacle, and at first his efforts appeared remarkably successful. He formed a large spider establishment, which, for a time, was very prosperous. Having ordered all the short-legged spiders (which are the most industrious spinners) to be collected for him by persons employed for the purpose, he enclosed them in paper boxes, with pin-holes pricked in them to admit the air to the prisoners. The insects were regularly fed with flies, and prospered well on their diet. In due time most of them laid their eggs, and spun their silken bags. M. Bon affirmed that each female produced from six to seven hundred eggs, whereas the silkworm moth lays only about one hundred. He also stated, that out of seven hundred or eight hundred young spiders which he kept, scarcely one died in a year; while of one hundred silkworms, not forty lived to form their cocoons.
These favourable statements led the Royal Academy of Paris to take the subject into consideration, and Réaumur was appointed to inquire into the merits of the new scheme. This careful inquirer found many serious obstacles in the way of such establishments. The fierceness of spiders, and their propensity to destroy each other, were noticed as unfitting them to be bred and reared together. On distributing about five thousand spiders in cells, in companies of about fifty or a hundred, it was found that the larger spiders quickly killed and ate the smaller, until there were only one or two occupiers of each cell. The silk of the spider was also found inferior in lustre and strength to that of the silkworm, and had the disadvantage of being incapable of winding off the ball, but must necessarily be carded.
GARDEN SPIDER—(Natural Size.)
Indeed, it could require no very great consideration to decide, that spiders’ silk, when compared with that of the silkworm, was vastly inferior for manufacturing purposes, though employed in many useful and highly ingenious ways by the insect itself. A few of these we must not omit to notice. Every one must have seen the common garden spider (Epeira diadema) suspended by its silken rope, or forming its beautiful web; but every one is not aware that that silken rope is made up of a multiplicity of threads, and that when the spider attaches the rope to any object by pressing her spinneret against it, she spreads out these threads over an area of some diameter, thus securing a much greater degree of strength than could be gained by merely fixing her thread to one point. This contrivance may be seen best when the threads are attached to a black object. Under the microscope they appear thus:—
SPIDER’S METHOD OF ATTACHING HER THREAD.
The uses of silk in the webs and nests of common spiders are too obvious to be dwelt on, but there is a most clever and surprising adaptation of the same material by several foreign species of spider which must be briefly stated. In the Ionian islands, and also in the West Indies, there are found certain spiders, commonly known as trap-door spiders, which make a cylindrical nest in the earth, and cover the entrance with a door of their own construction, framed of alternate layers of silk and earth, and fastened to the opening by a hinge of stout silk. These spiders also line their nests throughout with numerous layers of silken web to the thickness of stout cartridge paper, and finish it with the greatest care. This beautiful lining is yet further strengthened in particular parts, where the nest is likely to be exposed to danger. But the greatest amount of skill and care is bestowed upon the trap-door and its silken hinge. This door is about the eighth of an inch thick, rough on the outside, not much unlike an oyster shell, which it also resembles in being thick and strong near the hinge, but thinner towards the circumference. The breadth of this hinge is various, but sometimes it is very considerable, as shown in the accompanying figure. It also possesses great elastic force, so that on being opened, it closes again of itself. This is principally accomplished by a fold or doubling of the web, at each end of the hinge, which permits the door to be opened nearly to a right angle with the aperture, but no farther, unless violence be used. The under side of the door is perfectly smooth and firm, being shaped so as to fit accurately, and yet to offer no resistance when pushed open by the insect.
TRAP-DOOR SPIDER.
NEST OF TRAP-DOOR SPIDER.
TRAP-DOOR OPENING BY A LEVER.
As might be expected, there are varieties in the shape and size of these nests. Some specimens found in the island of Zante had the silken layers of the lid extended into a sort of handle or lever just above the hinge, on pressing which in ever so slight a degree the trap-door opened. From this it would appear that the entrance to such a nest could be effected as easily by the enemies of the spider as by the spider itself: this, however, is not the case; for repeated observation has shown that the spider keeps guard at the entrance, and actually holds the door with her fore feet and palpi, while the hinder feet are extended down the side of the nest, and the mandibles are thrust into the opposite side near the door. By this means the insect gets such power as to resist with considerable force the opening of the door. If it be asked how this is known, we are able to refer to the experiments of careful observers, who extracted a number of nests from the ground, and opening them at the lower end, looked up, and saw the spider so occupied. A sectional view of the nest will show that the curved form of the cover, and the shape of the side walls, must favour this method of keeping the door shut. In some cases, small hollows were formed round the interior edge of the lid, into which the spider thrust its feet when keeping guard. It is a curious fact, that when several of these spiders enclosed in their nests were kept as a matter of curiosity in a box of earth, and the doors frequently opened to examine their proceedings, one or two of them, as if wearied at these repeated interruptions, effectually closed their doors by weaving a piece of silken tapestry, which was spread over the interior of the opening, and rounded like the inside of a thimble. This was so strongly attached to the door and to the side walls, that no opening could be made without destroying the nest.
SECTION OF NEST.
It was long a matter of surprise to the observer to find, that in the case of some nests, and not of others, there was a trap-door at the bottom as well as at the top of the nest: this was at last explained by the following fact. A spider’s nest, which was accidentally broken off in being extracted from the ground, was purposely restored to the earth in a reversed position, with the trap-door downwards, and the broken and exposed part level with the surface. The spider immediately set to work to make a new door over the broken part, and finished it with as much completeness as the other. Doubtless, then, those nests which were provided with two doors were such as had been upset and broken. This is the more likely because in Zante, where such nests were found, the earth is annually dug up round the roots of the olive tree, a favourite nesting place of these trap-door spiders.
NEST WITH TWO OPENINGS.
We must not omit to mention, that in some parts of South America, especially in Paraguay, there is a spider which forms a spherical cocoon for its eggs, an inch in diameter, of a yellow silk, which the inhabitants spin on account of the permanency of the colour. It must also be observed that the silk of spiders is useful to the astronomer, who employs the strongest thread (the one, namely, which supports the web) for the divisions of the micrometer. By its ductility, this thread acquires about a fifth of its ordinary length.
WHITE WAX INSECT OF CHINA.
CHAPTER IV.
MANUFACTURE OF WAX BY THE HIVE BEE, THE HUMBLE BEE, AND THE WHITE WAX INSECT OF CHINA.
GRUB IN CELL.
The most notable insect manufacturer, after the silkworm, is the common hive bee, which is able to produce three distinct substances, honey, wax, and silk; the first two only being useful to mankind. Persons who have never seen bees in any other than their perfect state, and are unacquainted with the internal economy of the hive, will learn with surprise that the first appearance of this insect is that of a small straight worm, which rapidly increases in size until it touches the sides of the cell which forms its dwelling-place. It then coils itself up, until the extremities meet and form a complete ring. When it ceases eating, the nurse-bees seal up the cell, leaving the caterpillar to spin its cocoon in safety. The silken film in which the insect now begins to wrap itself, proceeds from a spinner, situated in the middle part of the under lip, and is composed of two threads, gummed together as they issue from the two orifices of the spinner. The caterpillar is employed during thirty-six hours in making its cocoon; three days after which it becomes a chrysalis. Over this chrysalis, or rather over the cell in which it is contained, the nurse-bees brood until the warmth of their bodies penetrates, and assists in producing the last change of the insect within. The cocoon, by degrees, becomes attached to the interior of the cell like a lining, and the bee, having its parts gradually unfolded, begins at length to cut its way through the cover of the cell. It is now a perfect bee, and capable at once of taking its part in the labours of the hive. These labours chiefly relate to food, shelter, and care of the young. In the article of food, the bee is a most industrious collector of the sweet juices of flowers, which are converted into the luscious honey with which she stores her hive. She also collects pollen, as an ingredient in the food of the young, and a gummy substance called propolis, which oozes from the poplar, birch, and willow, and which she uses as a sort of varnish and cement to the projecting parts of the hive.
BEES GATHERING HONEY.
HEAD OF BEE.
(Magnified.)
For the purpose of collecting, carrying home, and manufacturing these several products, the working bee is provided with a complete and beautiful apparatus, consisting of a proboscis (almost as wonderful in its way as that of the elephant), by which she ascertains the nature of food, and imbibes such as is adapted to her wants; a honey bag, or second stomach, which is a small transparent globe about the size of a pea, where she deposits her nectar; a pair of baskets, one in each hind leg, in which she stores the pollen of flowers, and the propolis or gum of trees; and lastly, in the case of the wax-makers, four pairs of wax pockets, or membranous bags, contained in the abdomen, where by some unknown process wax is secreted from the food taken into the stomach. What an astonishing provision for the requirements of a single insect!
HIND LEG OF WORKER.
a, the haunch; b, the thigh; c, the tibia, or pallet, containing the basket or cavity; d, e, the foot.