Fig. 192.—The Convolvulus Sphinx (Sphinx convolvuli).This is the mission of science, to dissipate the thousands of prejudices and dangerous superstitions which mislead ignorant people.Fig. 193.—Death's-head Hawk-MothFig. 193.—Death's-head Hawk-Moth (Acherontia atropos).This moth has the front wings of a blackish brown colour, having lighter irregular bands varied with brown and grey, above and below. On the middle of the front wing there is a well-defined white dot. The hind wings have two black bands, the upper narrower than the lower one; the rest of the wing is a fine yellow. The abdomen has likewise from five to six yellow and as many black bands; in the middle is a long blackish longitudinal band. This moth is not very rare, and may be found in autumn. Its flight is heavy, and, as we have said, the insect never flies till after sunset. If caught, or when teased, it utters a cry which is very audible.The death's-head hawk-moth would be a very inoffensive being if it did not make its way into bee-hives, in order to steal the honey, of which it is excessively fond. It is to no purpose that the bees dart their stings at the intruder, they only blunt them against its thick skin, and soon, terrified at its presence, disperse on all sides.Fig. 194.—Larva of the Death's-head Hawk-MothFig. 194.—Larva of the Death's-head Hawk-Moth (Acherontia atropos).The caterpillar of theAcherontia atropos(Fig. 194) is the largest of all European caterpillars. It attains to as much as four and a half inches in length by eight lines in diameter. Its colour is lemon yellow, which changes into green on the sides and belly. From the fourth to the tenth ring inclusively it is ornamented laterally with seven oblique bands of an azure blue, which are tinted with violet, and bordered with white on the side. These bands joining together over the back of each segment resemble so manychevronsplaced parallel to eachother. The body is, moreover, dotted with black. At its extremity is a yellow horn, curved back like a hook, and covered with tubercles. The head is green, and marked laterally with a black stripe. It lives chiefly on the potato, and theLycium barbarum, sometimes called the tea-tree, a shrub belonging to theSolanaceæ. It buries itself in the earth to change into a chrysalis (Fig. 195) of a bright chestnut brown.Fig. 195.—Chrysalis of the Death's-head Hawk-Moth.Fig. 195.—Chrysalis of the Death's-head Hawk-Moth.Fig. 196.—Lime Hawk-MothFig. 196.—Lime Hawk-Moth (Smerinthus tiliæ).Fig. 197.—Larva of the Lime Hawk-MothFig. 197.—Larva of the Lime Hawk-Moth (Smerinthus tiliæ).Fig. 198.—Eyed Hawk-MothFig. 198.—Eyed Hawk-Moth (Smerinthus ocellatus).We will mention still further, in the family of theSphingidæ, three species of the genusSmerinthus, which fly heavily and by twilight.The Lime-tree Hawk-moth (Smerinthus tiliæ,Fig. 196) has its upper wings grey with some shades of green, and moreover, in the middle of the wing an irregular band of a brownish green colour. The thorax, covered with hairs, is grey, with three green longitudinal bands. The abdomen is also grey. The moth flies heavily after sunset, and is found on the trunks of trees during the months of May and June. The larva (Fig. 197) is glaucous green dotted with yellow, and marked on each side with seven oblique lines of the same colours. Its wrinkly horn is blue above and yellow below. It is found on the lime and the elm. It buries itself at the foot of the tree on which it has fed to change into a chrysalis without making a cocoon.Fig. 199.—Poplar Hawk-MothFig. 199.—Poplar Hawk-Moth (Smerinthus populi).We will content ourselves by here giving drawings of two other species of the same genus: the Eyed Hawk-Moth (Smerinthus ocellatus,Fig. 198), which is not rare during the months of May and sometimes August, the caterpillar of which lives on the leaves of willows, poplars, and fruit-trees; and the Poplar Hawk-Moth (Smerinthus populi,Fig. 199), whose caterpillar (Fig. 200) lives on the poplar, the aspen, and sometimes on the willow and birch.The division ofBombycinacontains the largest of moths, and atthe same time species of a middle and small size. These moths take no nourishment, and live only for a short time—long enough to propagate their species. They rarely fly during the day, only showing themselves in the evening. The group is dispersed over nearly all parts of the world, and may be recognised by the antennæ generally being cut like the teeth of a comb in the males, by their thick, strong bodies, and, in the majority of cases, by their large head, by their wings more or less large, and by their heavy flight.Fig. 200.—Larva of the Poplar Hawk-MothFig. 200.—Larva of the Poplar Hawk-Moth (Smerinthus populi).In theBombycinaare found the generaSericaria,Attacus,Bombyx,Orgyia,Liparis, &c.It is to the genusBombyxthat the silkworm belongs, that celebrated insect called by LinnæusBombyx mori, a name which reminds us at the same time of its most ancient denomination, and of the mulberry tree, on which these caterpillars feed.M. Guérin-Méneville has called the silkworm "the dog of insects," for it has been domesticated from the most ancient times, and has become deprived of great part of its strength in the process. The moth of the silkworm can no longer keep its position in the air, or on the leaves of the mulberry when they are agitated by the wind. It can no longer protect itself, under the leaves, from the burning heat of the sun and from its enemies. The female, always motionless,seems to be ignorant of the fact that she has wings. The male no longer flies; he flutters round his companion, without quitting the ground. It ought, however, to be possessed in the wild state of a sufficiently powerful flight. M. Ch. Martins found that after three generations reared in the open air, the males recovered their lost power.Before speaking of the different phases of the life of the silkworm and the rearing of this precious insect, we will notice the origin and progress of the silk trade, one of the most important branches of commerce in the South of Europe and in the East.The native country of the silkworm is not better known than that of the greater number of plants and animals which form the staple of agricultural industry. Probably, however, it was China. It was certainly in this vast empire that long since the business of fabricating silk began. One reads the following in "L'Histoire générale de la Chine," by M. Mailla:—"The Emperor Hoang-ti, who lived 2,600 years before our era, wished that Si-ling-chi, his wife, should contribute to the happiness of his people; he charged her to study the silkworm, and to try to utilise its threads. Si-ling-chi caused a great quantity of these insects to be collected, which she fed herself in a place destined exclusively for the purpose; she not only discovered the means of rearing them, but still further the manner of winding off their silk and of employing it in the manufacture of fabrics."It may be asked, however, if the learned men who composed this recital did not collect under the reign of the emperor Hoang-ti all the events and all the discoveries whose dates were lost in the obscurity of the most remote periods of history. Is not the Empress Si-ling-chi a mythical person? a sort of Chinese Ceres, to whom, under the title of goddess of the silkworm, they then raised altars?Here, at any rate, is how Duhalde[50]analyses the recital of the Chinese annalists on the remarkable fact of the introduction of the silkworm and its rich products into the Chinese empire:—"Up to the time of this queen (Si-ling-chi)," says he, "when the country was only lately cleared and brought into cultivation, the people employed the skins of animals as clothes. But these skins were no longer sufficient for the multitude of the inhabitants; necessity made them industrious; they applied themselves to the manufacture of cloth wherewith to cover themselves. But it was to this princess that they owed the useful invention of silk stuffs. Afterwards,the empress, named by Chinese authors, according to the order of their dynasties, found an agreeable occupation in superintending the hatching, rearing, and feeding of silkworms, in making silk, and working it up when made. There was an enclosure attached to the palace for the cultivation of mulberry trees."The empress, accompanied by queens and the greatest ladies of the court, went in state into this inclosure, and gathered with her own hand the leaves of three branches which her ladies in waiting had lowered till they were within her reach; the finest pieces of silk which she made herself, or which were made by her orders and under her own eye, were destined for the ceremony of the grand sacrifice offered to Chang-si. (Plate V.)"It is probable," adds Duhalde, "that policy had more to do than anything else with all this trouble taken by the empresses. Their intention was to induce, by their example, the princesses and ladies of quality, and the whole people, to rear silkworms: in the same way as the emperors, to ennoble in some sort agriculture, and to encourage the people to undertake laborious works, never failed, at the beginning of each spring, to guide the plough in person, and with great state to plough up a few furrows, and in these sow someseed."As far as concerns the empresses, it is a long time since they have ceased to apply themselves to the manufacture of silk; one sees, nevertheless, in the precincts of the imperial palace, a large space covered with houses, the road leading to which is still called the road which leads to the place destined for the rearing of silkworms, for the amusement of the empresses and queens. In the books of the philosopher Mencius, is a wise police rule, made under the first reigns, which determines the space destined for the cultivation of mulberry trees, according to the extent of the land possessed by each private individual."M. Stanislas Julien[51]tells us of many regulations made by the Emperor of China, to render obligatory the care and attention requisite to rearing silk.Tchin-iu, being governor of the district of Kien-Si, ordered that every man should plant fifty feet of land with mulberry trees.[52]The Emperor (under the dynasty of Witei) gave to each man twenty acresof land on condition that he planted fifty feet with mulberry trees.[53]Hien-tsang (who ascended the throne in 806) ordered that the inhabitants of the country should plant two feet in every acre with mulberry trees.[54]The first Emperor of the dynasty of Song (who began to reign about the year 960) published a decree forbidding his subjects to cut down the mulberry trees.[55]V.—The Empress Si-ling-chi gathering Mulberry Leaves.V.—The Empress Si-ling-chi gathering Mulberry Leaves.By all these means, according to the testimony of M. Stanislas Julien, the business of the fabrication of silk became general in China. This great empire soon furnished its neighbours with this precious textile material, and created for its own profit a very important branch of commerce.It was forbidden, under pain of death, to export from China the silkworm's eggs, or to furnish the necessary information in the art of obtaining the textile material. The manufactured article only could be sold out of the empire. It was thus that the Asiatic nations very soon understood silk; and that in many of their cities they applied themselves to weaving stuffs of this precious substance. The carpets and dyed stuffs of Babylon, mixed with gold and silk, enjoyed in ancient times an unparalleled renown. China was not, however, the only country that then furnished silk to the towns of Asia Minor. At a very distant period India sent by her caravans very considerable quantities of it. M. Émile Blanchard (of the Institute) remarks, however, that the tissues of India must be made of a different silk from that of China, that is to say, of a silk of some of thoseBombycesof which the public has been told so much of late years, and of which we shall have soon to speak.Silk commanded for centuries a prodigiously high price. In the time of Alexander its value in Greece was exactly its own weight in gold, and so it was very parsimoniously employed in silk tissues. These were so transparent that women who wore them were scarcely covered.Silk was unknown to the Romans before Julius Cæsar. It was to him that Rome owed its acquaintance with this new material. He introduced it, moreover, in a singularly magnificent manner. One day, at afêtegiven in the Colosseum—a combat of animals and gladiators—the people saw the coarse tent of cloth, intended to keep off the rays of the sun, replaced by a magnificent covering of Oriental silk. They murmured at this gorgeous prodigality, but declaredCæsar a great man. The introduction of silk among the Romans was the signal for luxurious expenditure. The patricians made a great display with their silk cloaks of incalculable value; so that, from the time of Tiberius, the Senate felt itself called upon to forbid the use of silk garments to men. Examples of simplicity are sometimes set in high places; thus, the Emperor Aurelian refused to the Empress Severina so costly a dress.The commerce in silk bore doubly hard upon Europe, both on account of the value of the material and of the great use which was made of it. Persia was the emporium, and had the monopoly of this merchandise. The Emperor Justinian I., who reigned at Constantinople fromA.D.527 to 565, tried all the means within his power of freeing his States from this ruinous tyranny, when a circumstance occurred, very fortunately for the national commerce, which brought about the introduction into Europe of sericulture, or the cultivation of silk.Two monks of the order of St. Basil, in their ardour for the propagation of the faith, had pushed forwards into China. There they had been initiated into the operations which furnished the fabric so highly prized. On their return to Constantinople, and hearing of the project that Justinian entertained of depriving the Persians of the monopoly in silk, the two monks proposed to the Emperor to enrich his state by introducing the art of fabricating this material. The proposition was greedily accepted, and the two monks returned again to China, with the object of procuring the eggs of the insect. Having arrived at the end of their journey, they succeeded in getting possession of a quantity of silkworms' eggs. They hid them between the knots of their sticks, and started back to their native country, without being once interfered with. Two years afterwards they re-entered Constantinople with their precious booty.[56]The larva were fed on mulberry leaves. Immediately afterwards began the rearing of the worms and the preparation of the silk, according to the instructions given by these courageous travellers. The first broods succeeded perfectly, and so plantations of mulberry trees were seen to multiply and spread through the whole extent of the Eastern Empire. It was, above all, in Southern Greece that this branch of industry assumed an immense importance. It was then the Peloponnesus lost its old name, and was called the Morea, from the Latin name for "mulberry,"morus.[57]Constantinople and Greece, during centuries, furnished the whole of Europe with silkworms. This diffusion, however, was effected very slowly. The Greeks attached great importance to retaining the monopoly, and the emperor Justinian had caused to be established at Constantinople itself silk manufactories, where the most skilful artificers of Asia, who were forbidden to reveal the various processes to strangers, worked.Towards the beginning of the eighth century the Arabs introduced the silkworm into Spain. But this industry remained confined within narrow limits. It was in fact not till after the twelfth century that sericulture began to spread throughout Europe. Roger, King of the Two Sicilies, possessing a navy that commanded the Mediterranean, employed it chiefly in making excursions and conquests. He ravaged Greece, and, not satisfied with the booty he carried away from that unfortunate country, wished still further to deprive them, for the good of his own kingdom, of the silk monopoly, the source of their riches. Roger carried away into Sicily and Naples a great number of prisoners, amongst whom were some weavers and men who had devoted themselves to the rearing of silkworms. In 1169 he established these workmen in houses adjoining his own palace at Palermo. There they dyed the silk of different colours, and mixed it with gold, pearls, and precious stones.From Sicily the art of preparing silk spread over the rest of Italy. In 1204 the workers in silk constituted themselves into a syndicate at Florence. It is not, however, till 1423—more than two hundred years after the introduction of this branch of industry into Italy—that we find the first mention of the cultivation of the mulberry tree in Tuscany. In 1440 each Tuscan peasant was forced to plant at least five mulberry trees on the land he cultivated. In 1474 the commerce in silk fabrics with all parts of the world had become extremely prosperous at Florence. In 1314 the Venetian manufactures began to assume much importance. Three thousand workers in silk were then established in Venice.Without dwelling longer on the propagation of the silk trade in Italy, let us pass on to its establishment in France. It was in 1340 that some French gentlemen, who had stayed some time in Naples, planted in Avignon the first mulberry trees.[58]According to Olivierde Serres, it was not introduced till much later into Dauphiné. It was not introduced into Alan, near Montelimart, till 1495, by the Seigneur Guyape de Saint-Aubain.[59]Louis XI. made great efforts to develop the silk trade in France, by inviting over Italian workmen; and they began under his reign to fabricate silks in Touraine and Lyons. Francis I. greatly developed the trade of Lyons. In 1554, under Henry II., the masters and men employed in the manufacture of gold, silver, and silk in Lyons were twelve thousand in number. Under Henry II. were planted the mulberry trees of Bourdezière, Tours, Chenonceaux, Toulouse, and Moulins. These plantations, however, were of very small extent. They were not the result of a general and truly popular effort; moreover, civil war came very soon, and turned men's minds away from the isolated attempts of some few private individuals. Sericulture, in fact, did not assume any great importance in France till the reign of Henry IV.This king saw with grief considerable sums of money leaving France each year for the purchase of raw silk or of silk stuffs. Two men marvellously furthered his project of encouraging the silk trade. One of these men was Barthelemy Laffemas, calledBeausemblant. For a long time he had been writing memoir upon memoir, to demonstrate the advantages to be derived from the plantation of the mulberry tree in France; and he tells us that silkworms were then raised with success at Nantes, at Poissy, and even at Paris. The second supporter whom Henry IV. found in the propagation of sericulture was a man distinguished in a very different way from that of M. Laffemas. This was Olivier de Serres, the author of the "Théâtre de l'Agriculture;" he whom Henry IV. called hislord and master in agriculture. Olivier de Serres was the first among his countrymen who had published instructions regarding the cultivation of mulberry trees and the rearing of silkworms. Henry IV., who had noticed his writings, called him to Paris; and, on his solicitation, caused twenty thousand mulberry trees and a great quantity of silkworms' eggs, of which a distribution was made over the whole of France, to be imported from Italy. From that moment, sericulture was propagated rapidly in the Cévennes, in Provence, in Languedoc, in Touraine, and many other provinces. Mulberry trees were planted at Fontainebleau, in the royal park of Tournelles, and even in the Tuileries, where an Italian lady, named Julle, reared silkworms for Henry IV.Notwithstanding this great impulse, sericulture dwindled awayon the death of that king. It received a fresh impulse under Colbert, the great minister, who succeeded in creating the spirit of commerce and trade in France. New manufactories were established, and plantations of mulberry trees formed in many of the provinces. All this progress was suddenly brought to a standstill by the iniquitous revocation of the Edict of Nantes, which deprived France of her leading commercial men. Driven from their own country, the Protestant families of the Cévennes established abroad silk manufactories, the fabrics of which rivalled those of French production.In the eighteenth century the intendants of the provinces tried, but with very slight success, to give a fresh impetus to sericulture in France. The Abbé Boissier de Sauvages published, about 1760, some works, which prove him to have been a patient observer, an accurate reasoner, and a clever rearer of silkworms. Boissier de Sauvages is the father of modern silk-culture. During the first Revolution, men's minds were occupied with graver subjects than the cultivation of the mulberry tree. But, on the return of peace, they got to work again on all sides. In 1808, the minister Chaptal estimated the weight of the cocoon harvest at between five or six thousand kilogrammes; whilst the invention of the Jacquard loom gave an immense impulse to the weaving of silk stuffs. Amongst those who introduced and benefited the art of sericulture, we must not forget Dandolo. Dandolo, who was born at Venice in 1758, and died in 1819, was the first who, at the beginning of this century, applied himself seriously to the amelioration of the processes employed in the cultivation of silk. He endeavoured to regulate the temperature, to introduce more order into the distribution of the food to the worms, to have more spacious premises, and to have these properly ventilated.Now we are on this subject, we must mention the names of those who at the present day have rendered important services to sericulture—such as M. Camille Beauvais, who raised silkworm rearing from the inactivity into which it had been plunged; M. Eugène Robert, who founded in the south of France the first successful silkworm nursery; M. Guérin-Méneville, who has devoted his life to the study of the same question, and to whom Europe owes the introduction and the acclimatisation of some species which will render us, perhaps, one day very great services; and lastly, M. Robinet, who has elucidated several practical questions in the art of sericulture. In bringing to a close this rapid historical epitome, we will state that France consumes annually 30,000 kilogrammes of silkworms' eggs, each kilogramme being at the present time worth from 300 to 500francs, and even more. The value of manufactured silks represents annually about 8,000,000 francs; and we find by official statistics that France exported in 1863 silk stuffs to the value of 384,000,000 francs. This immense trade shows how much silk is now-a-days everywhere appreciated; in those numerous tissues called taffeta, satin, and velvet, each of which seems to have a charm—a peculiar attraction. The consistency of the stuff, the smoothness, the softness of surface, the manner in which silk receives colours, the brightness, fineness, power of reflecting, the rustling, the light or heavy folds,—all these are beauty, elegance, and luxury, in whatever way these words are understood.TheBombyx morihas, however, nothing alluring in its appearance. Other caterpillars of the genusBombyxhave brilliant liveries; they are adorned with spots, blue as sapphires, green as emeralds, red as rubies, but produce threads without brightness and fineness. The humble silkworm, in a white blouse, like a workman, has nothing brilliant in its dress, and yet it gives to the whole world its most beautiful and gorgeous array. The body of the silkworm is composed of thirteen distinct segments. In front are three pairs of articulated legs, which will become later those of the moth. In the middle and towards the posterior part, are five pairs of membranous legs, furnished with a circle of very fine bristles, which assist the animal to hook itself on to leaves and stalks. On the two sides of its body are eighteen stigmata, or respiratory mouths.The head of the silkworm is remarkable; it is scaly, horny, and formed of one single piece. The mouth is provided with six small articulated pieces. Below is a simple blade, the upper lip, having in its middle a hollow, into which the animal causes the edge of the leaf it is gnawing to enter, and holds it thus without any exertion. Underneath the lip are inserted two large jaws, which cut the leaf as a pair of scissors. Underneath, some weaker jaws divide the fragments, and a little organ, articulated on to each jaw, that is to say, a palpus, pushes them back towards the mouth, and prevents the smallest particle of the leaf from falling. And lastly, in the space comprised between the two jaws, is an under-lip, which completely closes the mouth below. At the extremity of this piece may be seen a little prolongation, a sort of papilla, pierced with a hole, which is the orifice that gives issue to the silky thread.The organs which serve for the elaboration and emission of the silk have a peculiar interest for us. If we dissect a silkworm under water, we succeed, sooner or later, after having removed the outer parts, in laying bare a double apparatus, placed along the two sidesof the intestinal canal and below it. This is the apparatus which secretes the silk; it is the double silk-bearing gland. Each one of these glands is composed of a tube formed of three distinct parts (Fig. 201). The part which is nearest to the tail of the worm is a bent tube,A B C, of a thirtieth of an inch in diameter, and about nine inches in length, twisted a great many times into irregular zig-zags. This part of the silk-producing organ is continued in an enlarged portion,D E, which is the reservoir of the silky matter. To the extremity,E, of this reservoir, is attached another capillary tube,E F. These two capillary tubes, proceeding from the two glands, unite together like two venous trunks, as the plate shows, in one single, short canal,F, which opens in the mouth of the worm, at its under-lip.Fig. 201.Silk secreting apparatus.It is in the narrow hinder tubes that the silky matter is formed. It collects in the swollen part,D E, which is, properly speaking, the reservoir; and remains there in the glutinous state. Having reached the capillary tubes, it begins to assume consistency, and forms two threads, which are united together at the point of junction of the tubes, and come out through the orifice, with the appearance of a single thread, to be conducted and directed by the animal to those points it has selected.It was hoped that by taking from the body of the worm the viscous matter contained in the glands, silk could be formed. But this hope was disappointed. It was found possible, it is true, to take the silk out; to draw it out into threads more or less fine; but up to this time it has only been possible in this way to obtain a matter which, when dried, more or less resembles catgut, and is easily enough spoilt by water.The viscous substance contained in the glands must then be elaborated by the insect itself. When it arrives in the conduit common to the capillary tubes, under the form of a thread, it is impregnated with a sort of varnish, which is poured into them from two neighbouring glands. The varnish unites the two threads into one single thread, and imparts to it the brilliancy of silk, and the property of resisting the action of water. It is during the last phases of the worm's development that the silky matter becomes abundant in theglands. At this period the animal eats much; and it is certain that the substance to be converted is furnished by the leaf of the tree on which the insect feeds.In consequence of this having been remarked, some manufacturers have attempted to obtain their silk directly from the mulberry leaf; but they only get a bad floss or refuse silk. This is because the silk is not formed in the mulberry leaf. The organs of insects are laboratories, in which manipulations unknown to man are carried on, manipulations which he has not been able to imitate.After this rapid glance at the fundamental parts of the organism of the silkworm, we will occupy ourselves with the natural history, properly so called, of this insect, and with its rearing, carried on with a view to the production of silk.As belonging to the first part of this programme, we have to speak of themoult, of theagesof the silkworm, of its maturity, of itsmountingorascending season, of the formation of the cocoon, of the chrysalis, of the moth, and the eggs.—Head of the Silkworm during moulting.Fig. 203.—Position of Silkworm while moulting.Fig. 202.Head of the Silkworm during moulting.Fig. 203.Position of Silkworm while moulting.The name moult has been given to a sort of crisis during which the renewing of the skin of larvæ takes place. When it approaches, the silkworm changes its colour. Its robe, which was white or grey, and opaque, becomes yellow and somewhat transparent. The head swells considerably, especially above, and the skin becomes wrinkled (Fig. 202). The worm then fasts, and prepares to cast its skin. It places here and there some silk threads on the surrounding objects. It then slips under these threads, so that during its movements the old skin which it will abandon is, so to speak, gathered up. It then assumes a peculiar position, that represented inFig. 203, and remains in it in a state of immobility which has been called sleep (sommeil).During this sleep the new skin is formed under the old. A liquid oozes forth between the two membranes which separates them, and allows the silkworm to leave its old skin. To effect this, the worm begins by raising its head, and by making contortions. The old skin splits round the muzzle, or snout, on the head and back; then bydifferent movements the animal emerges from its skin, which remains held up by the silken threads. The duration of the time occupied in moulting varies with the degree of the heat or humidity of the atmosphere; but in general the state ofsleeplasts from twelve to twenty-four hours. One hour after the crisis the worm begins again to eat.Fig. 204.Egg and firstage.Theagesof the silkworm are the periods of time which elapse between one moult and another. If we observe some silkworms when the temperature is favourable, we shall find that there are four moults, and consequently five ages. At the first age (Fig. 204), the silkworm is black and hairy; then of a nut colour at the moment when the first moult is going to take place. "The appearance presented by these worms collected together on a leaf," says Dandolo, "is that of a downy surface of a dark chestnut colour, in the midst of which one sees nothing but a movement of little animals having their heads raised, working them about, and presenting black, shiny muzzles. Their bodies are completely covered with hairs arranged in straight lines, between which one perceives along the whole length of the body other longer hairs."[60]Fig. 205.Second age.Fig. 206.Third age.Fig. 207.Fourth age.The first age lasts for five days. At the second (Fig. 205), the worm is grey, almost without down, then of a yellowish white, and one sees the crescents making their appearance on the second and fifth segment. At the third age (Fig. 206), there is not a single hair remaining, and the worm becomes whitish, and is always becoming lighter. The third age lasts six days, as does also the fourth (Fig. 207). At the fifth (Fig. 208), the worm has very nearly reached the end of its career in the caterpillar state, and now is the time of its greatest voracity. This age is the longest; it lasts nine days.At each of these periods in the life of the silkworm may beremarked a physiological fact to which has been given the name offrèze. When the silkworm has just moulted it eats little, but the time very soon arrives when it does so with extraordinary avidity. It is indeed insatiable. Thefrèzeof the last age is called thegrande frèze. It takes place about the seventh day. During this day worms, the produce of thirty grammes[61]of eggs, consume in weight as much as four horses, and the noise which their little jaws make resembles that of a very heavy shower of rain. It is at the end of this stage that the insect prepares the shelter in which is to be brought about its metamorphosis into a chrysalis.Fig. 208.—Fifth age.A little while before this it ceases to eat, turns yellow, and becomes as transparent as a grape. It is now said to have reached itsmaturity. Up to this moment the worm had never tried to leave its litter. It lived a sedentary life, and never thought of wandering away from its food. Now it is seized with an imperious desire for changing its quarters. It gets up, it roams about, and moves its head in all directions to find some place to cling on to. It walks over everything within its reach, particularly over those obstacles which are placed vertically. It aspires, not to descend, like the heroes of classic tragedy, but to rise. It is for this reason that this period of the silkworm's life has received the name of themountingorascending season. It now looks for a convenient place in which to establish its cocoon. Every one has remarked how the animal sets to work to accomplish its task. It begins by throwing from different sides threads destined for fixing the cocoon; this is what we callrefuse silk. The proper space having been circumscribed by this means, the worm begins to unwind its thread—a continuous thread of about a thousand mètres long.It has been calculated, let us say by the way, that forty thousand cocoons would suffice to surround the earth at the equator with one thread of silk. Folded on itself almost like a horse-shoe, its backwithin, its legs without, the worm arranges its thread all round its body, describing ovals with its head. It approximates gradually the points of attachment of the thread. As long as the cocoon is not very thick one can watch it through the meshes of the web applying and fixing its thread, still to a certain degree soft, in such a manner as to make it adhere closely to the parts already formed."We can state," says M. Robinet, "that the silkworm makes every second a movement extending over about five millimètres. The length of the threads being known, it follows that the worm moves its head three hundred thousand times in making its cocoon. If it employs seventy-two hours at its work, it is a hundred thousand movements every twenty-four hours, four thousand one hundred and sixty-six an hour, and sixty-nine a minute, that is to say, a little more than one a second."About the fourth day, after having expended all its silk,[62]the worm shut up in the cocoon becomes of a waxy white colour, and swollen in the middle of its body. The abdominal legs wither away; the six fore legs approach each other and become black. The parts of the mouth tend downwards; the skin wrinkles. Very soon it is detached and pushed down towards the hinder part, and the chrysalis appears under the rents in the skin. It is at first white, but speedily becomes of a brown red.The silkworm remains in general from fifteen to seventeen days in the pupa state. At the moment of hatching, the moth begins by breaking the skin in which it is shut up, and which is pretty thin. But how can it come out of the silky prison which it has itself built? To effect this it makes use of a peculiar liquid contained in a little bladder with which its head is provided, and which was discovered by M. Guérin-Méneville. It moistens the cocoon with this liquid; which soaks through and penetrates the whole thickness of the silken wall which confines it. The threads of silk of which it is composed are moistened and disunited, but not broken. The moth opens a passage for itself through the threads thus separated, and makes its appearance in the light of day. Its wings are folded back on themselves, and it is still quite wet, but it seeks immediately for a good place in which to dry itself, and in a little time assumes its final appearance (Figs.209,210). The female (Fig. 210) has whitish wings, the antennæ only slightly developed and pale, the abdomen voluminous, cylindrical, and well filled. It is quiet, heavy, and stationary. The male is smaller; its wings are tinged with grey,its antennæ blackish; it moves about, beats its wings together, and is lively and petulant.Fig. 253.—Silkworm Moth (Bombyx mori), male.
Fig. 192.—The Convolvulus Sphinx (Sphinx convolvuli).
This is the mission of science, to dissipate the thousands of prejudices and dangerous superstitions which mislead ignorant people.
Fig. 193.—Death's-head Hawk-MothFig. 193.—Death's-head Hawk-Moth (Acherontia atropos).
This moth has the front wings of a blackish brown colour, having lighter irregular bands varied with brown and grey, above and below. On the middle of the front wing there is a well-defined white dot. The hind wings have two black bands, the upper narrower than the lower one; the rest of the wing is a fine yellow. The abdomen has likewise from five to six yellow and as many black bands; in the middle is a long blackish longitudinal band. This moth is not very rare, and may be found in autumn. Its flight is heavy, and, as we have said, the insect never flies till after sunset. If caught, or when teased, it utters a cry which is very audible.
The death's-head hawk-moth would be a very inoffensive being if it did not make its way into bee-hives, in order to steal the honey, of which it is excessively fond. It is to no purpose that the bees dart their stings at the intruder, they only blunt them against its thick skin, and soon, terrified at its presence, disperse on all sides.
Fig. 194.—Larva of the Death's-head Hawk-MothFig. 194.—Larva of the Death's-head Hawk-Moth (Acherontia atropos).
The caterpillar of theAcherontia atropos(Fig. 194) is the largest of all European caterpillars. It attains to as much as four and a half inches in length by eight lines in diameter. Its colour is lemon yellow, which changes into green on the sides and belly. From the fourth to the tenth ring inclusively it is ornamented laterally with seven oblique bands of an azure blue, which are tinted with violet, and bordered with white on the side. These bands joining together over the back of each segment resemble so manychevronsplaced parallel to eachother. The body is, moreover, dotted with black. At its extremity is a yellow horn, curved back like a hook, and covered with tubercles. The head is green, and marked laterally with a black stripe. It lives chiefly on the potato, and theLycium barbarum, sometimes called the tea-tree, a shrub belonging to theSolanaceæ. It buries itself in the earth to change into a chrysalis (Fig. 195) of a bright chestnut brown.
Fig. 195.—Chrysalis of the Death's-head Hawk-Moth.Fig. 195.—Chrysalis of the Death's-head Hawk-Moth.
Fig. 196.—Lime Hawk-MothFig. 196.—Lime Hawk-Moth (Smerinthus tiliæ).
Fig. 197.—Larva of the Lime Hawk-MothFig. 197.—Larva of the Lime Hawk-Moth (Smerinthus tiliæ).
Fig. 198.—Eyed Hawk-MothFig. 198.—Eyed Hawk-Moth (Smerinthus ocellatus).
We will mention still further, in the family of theSphingidæ, three species of the genusSmerinthus, which fly heavily and by twilight.
The Lime-tree Hawk-moth (Smerinthus tiliæ,Fig. 196) has its upper wings grey with some shades of green, and moreover, in the middle of the wing an irregular band of a brownish green colour. The thorax, covered with hairs, is grey, with three green longitudinal bands. The abdomen is also grey. The moth flies heavily after sunset, and is found on the trunks of trees during the months of May and June. The larva (Fig. 197) is glaucous green dotted with yellow, and marked on each side with seven oblique lines of the same colours. Its wrinkly horn is blue above and yellow below. It is found on the lime and the elm. It buries itself at the foot of the tree on which it has fed to change into a chrysalis without making a cocoon.
Fig. 199.—Poplar Hawk-MothFig. 199.—Poplar Hawk-Moth (Smerinthus populi).
We will content ourselves by here giving drawings of two other species of the same genus: the Eyed Hawk-Moth (Smerinthus ocellatus,Fig. 198), which is not rare during the months of May and sometimes August, the caterpillar of which lives on the leaves of willows, poplars, and fruit-trees; and the Poplar Hawk-Moth (Smerinthus populi,Fig. 199), whose caterpillar (Fig. 200) lives on the poplar, the aspen, and sometimes on the willow and birch.
The division ofBombycinacontains the largest of moths, and atthe same time species of a middle and small size. These moths take no nourishment, and live only for a short time—long enough to propagate their species. They rarely fly during the day, only showing themselves in the evening. The group is dispersed over nearly all parts of the world, and may be recognised by the antennæ generally being cut like the teeth of a comb in the males, by their thick, strong bodies, and, in the majority of cases, by their large head, by their wings more or less large, and by their heavy flight.
Fig. 200.—Larva of the Poplar Hawk-MothFig. 200.—Larva of the Poplar Hawk-Moth (Smerinthus populi).
In theBombycinaare found the generaSericaria,Attacus,Bombyx,Orgyia,Liparis, &c.
It is to the genusBombyxthat the silkworm belongs, that celebrated insect called by LinnæusBombyx mori, a name which reminds us at the same time of its most ancient denomination, and of the mulberry tree, on which these caterpillars feed.
M. Guérin-Méneville has called the silkworm "the dog of insects," for it has been domesticated from the most ancient times, and has become deprived of great part of its strength in the process. The moth of the silkworm can no longer keep its position in the air, or on the leaves of the mulberry when they are agitated by the wind. It can no longer protect itself, under the leaves, from the burning heat of the sun and from its enemies. The female, always motionless,seems to be ignorant of the fact that she has wings. The male no longer flies; he flutters round his companion, without quitting the ground. It ought, however, to be possessed in the wild state of a sufficiently powerful flight. M. Ch. Martins found that after three generations reared in the open air, the males recovered their lost power.
Before speaking of the different phases of the life of the silkworm and the rearing of this precious insect, we will notice the origin and progress of the silk trade, one of the most important branches of commerce in the South of Europe and in the East.
The native country of the silkworm is not better known than that of the greater number of plants and animals which form the staple of agricultural industry. Probably, however, it was China. It was certainly in this vast empire that long since the business of fabricating silk began. One reads the following in "L'Histoire générale de la Chine," by M. Mailla:—
"The Emperor Hoang-ti, who lived 2,600 years before our era, wished that Si-ling-chi, his wife, should contribute to the happiness of his people; he charged her to study the silkworm, and to try to utilise its threads. Si-ling-chi caused a great quantity of these insects to be collected, which she fed herself in a place destined exclusively for the purpose; she not only discovered the means of rearing them, but still further the manner of winding off their silk and of employing it in the manufacture of fabrics."
It may be asked, however, if the learned men who composed this recital did not collect under the reign of the emperor Hoang-ti all the events and all the discoveries whose dates were lost in the obscurity of the most remote periods of history. Is not the Empress Si-ling-chi a mythical person? a sort of Chinese Ceres, to whom, under the title of goddess of the silkworm, they then raised altars?
Here, at any rate, is how Duhalde[50]analyses the recital of the Chinese annalists on the remarkable fact of the introduction of the silkworm and its rich products into the Chinese empire:—
"Up to the time of this queen (Si-ling-chi)," says he, "when the country was only lately cleared and brought into cultivation, the people employed the skins of animals as clothes. But these skins were no longer sufficient for the multitude of the inhabitants; necessity made them industrious; they applied themselves to the manufacture of cloth wherewith to cover themselves. But it was to this princess that they owed the useful invention of silk stuffs. Afterwards,the empress, named by Chinese authors, according to the order of their dynasties, found an agreeable occupation in superintending the hatching, rearing, and feeding of silkworms, in making silk, and working it up when made. There was an enclosure attached to the palace for the cultivation of mulberry trees.
"The empress, accompanied by queens and the greatest ladies of the court, went in state into this inclosure, and gathered with her own hand the leaves of three branches which her ladies in waiting had lowered till they were within her reach; the finest pieces of silk which she made herself, or which were made by her orders and under her own eye, were destined for the ceremony of the grand sacrifice offered to Chang-si. (Plate V.)
"It is probable," adds Duhalde, "that policy had more to do than anything else with all this trouble taken by the empresses. Their intention was to induce, by their example, the princesses and ladies of quality, and the whole people, to rear silkworms: in the same way as the emperors, to ennoble in some sort agriculture, and to encourage the people to undertake laborious works, never failed, at the beginning of each spring, to guide the plough in person, and with great state to plough up a few furrows, and in these sow someseed.
"As far as concerns the empresses, it is a long time since they have ceased to apply themselves to the manufacture of silk; one sees, nevertheless, in the precincts of the imperial palace, a large space covered with houses, the road leading to which is still called the road which leads to the place destined for the rearing of silkworms, for the amusement of the empresses and queens. In the books of the philosopher Mencius, is a wise police rule, made under the first reigns, which determines the space destined for the cultivation of mulberry trees, according to the extent of the land possessed by each private individual."
M. Stanislas Julien[51]tells us of many regulations made by the Emperor of China, to render obligatory the care and attention requisite to rearing silk.
Tchin-iu, being governor of the district of Kien-Si, ordered that every man should plant fifty feet of land with mulberry trees.[52]The Emperor (under the dynasty of Witei) gave to each man twenty acresof land on condition that he planted fifty feet with mulberry trees.[53]Hien-tsang (who ascended the throne in 806) ordered that the inhabitants of the country should plant two feet in every acre with mulberry trees.[54]The first Emperor of the dynasty of Song (who began to reign about the year 960) published a decree forbidding his subjects to cut down the mulberry trees.[55]
V.—The Empress Si-ling-chi gathering Mulberry Leaves.V.—The Empress Si-ling-chi gathering Mulberry Leaves.
By all these means, according to the testimony of M. Stanislas Julien, the business of the fabrication of silk became general in China. This great empire soon furnished its neighbours with this precious textile material, and created for its own profit a very important branch of commerce.
It was forbidden, under pain of death, to export from China the silkworm's eggs, or to furnish the necessary information in the art of obtaining the textile material. The manufactured article only could be sold out of the empire. It was thus that the Asiatic nations very soon understood silk; and that in many of their cities they applied themselves to weaving stuffs of this precious substance. The carpets and dyed stuffs of Babylon, mixed with gold and silk, enjoyed in ancient times an unparalleled renown. China was not, however, the only country that then furnished silk to the towns of Asia Minor. At a very distant period India sent by her caravans very considerable quantities of it. M. Émile Blanchard (of the Institute) remarks, however, that the tissues of India must be made of a different silk from that of China, that is to say, of a silk of some of thoseBombycesof which the public has been told so much of late years, and of which we shall have soon to speak.
Silk commanded for centuries a prodigiously high price. In the time of Alexander its value in Greece was exactly its own weight in gold, and so it was very parsimoniously employed in silk tissues. These were so transparent that women who wore them were scarcely covered.
Silk was unknown to the Romans before Julius Cæsar. It was to him that Rome owed its acquaintance with this new material. He introduced it, moreover, in a singularly magnificent manner. One day, at afêtegiven in the Colosseum—a combat of animals and gladiators—the people saw the coarse tent of cloth, intended to keep off the rays of the sun, replaced by a magnificent covering of Oriental silk. They murmured at this gorgeous prodigality, but declaredCæsar a great man. The introduction of silk among the Romans was the signal for luxurious expenditure. The patricians made a great display with their silk cloaks of incalculable value; so that, from the time of Tiberius, the Senate felt itself called upon to forbid the use of silk garments to men. Examples of simplicity are sometimes set in high places; thus, the Emperor Aurelian refused to the Empress Severina so costly a dress.
The commerce in silk bore doubly hard upon Europe, both on account of the value of the material and of the great use which was made of it. Persia was the emporium, and had the monopoly of this merchandise. The Emperor Justinian I., who reigned at Constantinople fromA.D.527 to 565, tried all the means within his power of freeing his States from this ruinous tyranny, when a circumstance occurred, very fortunately for the national commerce, which brought about the introduction into Europe of sericulture, or the cultivation of silk.
Two monks of the order of St. Basil, in their ardour for the propagation of the faith, had pushed forwards into China. There they had been initiated into the operations which furnished the fabric so highly prized. On their return to Constantinople, and hearing of the project that Justinian entertained of depriving the Persians of the monopoly in silk, the two monks proposed to the Emperor to enrich his state by introducing the art of fabricating this material. The proposition was greedily accepted, and the two monks returned again to China, with the object of procuring the eggs of the insect. Having arrived at the end of their journey, they succeeded in getting possession of a quantity of silkworms' eggs. They hid them between the knots of their sticks, and started back to their native country, without being once interfered with. Two years afterwards they re-entered Constantinople with their precious booty.[56]The larva were fed on mulberry leaves. Immediately afterwards began the rearing of the worms and the preparation of the silk, according to the instructions given by these courageous travellers. The first broods succeeded perfectly, and so plantations of mulberry trees were seen to multiply and spread through the whole extent of the Eastern Empire. It was, above all, in Southern Greece that this branch of industry assumed an immense importance. It was then the Peloponnesus lost its old name, and was called the Morea, from the Latin name for "mulberry,"morus.[57]
Constantinople and Greece, during centuries, furnished the whole of Europe with silkworms. This diffusion, however, was effected very slowly. The Greeks attached great importance to retaining the monopoly, and the emperor Justinian had caused to be established at Constantinople itself silk manufactories, where the most skilful artificers of Asia, who were forbidden to reveal the various processes to strangers, worked.
Towards the beginning of the eighth century the Arabs introduced the silkworm into Spain. But this industry remained confined within narrow limits. It was in fact not till after the twelfth century that sericulture began to spread throughout Europe. Roger, King of the Two Sicilies, possessing a navy that commanded the Mediterranean, employed it chiefly in making excursions and conquests. He ravaged Greece, and, not satisfied with the booty he carried away from that unfortunate country, wished still further to deprive them, for the good of his own kingdom, of the silk monopoly, the source of their riches. Roger carried away into Sicily and Naples a great number of prisoners, amongst whom were some weavers and men who had devoted themselves to the rearing of silkworms. In 1169 he established these workmen in houses adjoining his own palace at Palermo. There they dyed the silk of different colours, and mixed it with gold, pearls, and precious stones.
From Sicily the art of preparing silk spread over the rest of Italy. In 1204 the workers in silk constituted themselves into a syndicate at Florence. It is not, however, till 1423—more than two hundred years after the introduction of this branch of industry into Italy—that we find the first mention of the cultivation of the mulberry tree in Tuscany. In 1440 each Tuscan peasant was forced to plant at least five mulberry trees on the land he cultivated. In 1474 the commerce in silk fabrics with all parts of the world had become extremely prosperous at Florence. In 1314 the Venetian manufactures began to assume much importance. Three thousand workers in silk were then established in Venice.
Without dwelling longer on the propagation of the silk trade in Italy, let us pass on to its establishment in France. It was in 1340 that some French gentlemen, who had stayed some time in Naples, planted in Avignon the first mulberry trees.[58]According to Olivierde Serres, it was not introduced till much later into Dauphiné. It was not introduced into Alan, near Montelimart, till 1495, by the Seigneur Guyape de Saint-Aubain.[59]Louis XI. made great efforts to develop the silk trade in France, by inviting over Italian workmen; and they began under his reign to fabricate silks in Touraine and Lyons. Francis I. greatly developed the trade of Lyons. In 1554, under Henry II., the masters and men employed in the manufacture of gold, silver, and silk in Lyons were twelve thousand in number. Under Henry II. were planted the mulberry trees of Bourdezière, Tours, Chenonceaux, Toulouse, and Moulins. These plantations, however, were of very small extent. They were not the result of a general and truly popular effort; moreover, civil war came very soon, and turned men's minds away from the isolated attempts of some few private individuals. Sericulture, in fact, did not assume any great importance in France till the reign of Henry IV.
This king saw with grief considerable sums of money leaving France each year for the purchase of raw silk or of silk stuffs. Two men marvellously furthered his project of encouraging the silk trade. One of these men was Barthelemy Laffemas, calledBeausemblant. For a long time he had been writing memoir upon memoir, to demonstrate the advantages to be derived from the plantation of the mulberry tree in France; and he tells us that silkworms were then raised with success at Nantes, at Poissy, and even at Paris. The second supporter whom Henry IV. found in the propagation of sericulture was a man distinguished in a very different way from that of M. Laffemas. This was Olivier de Serres, the author of the "Théâtre de l'Agriculture;" he whom Henry IV. called hislord and master in agriculture. Olivier de Serres was the first among his countrymen who had published instructions regarding the cultivation of mulberry trees and the rearing of silkworms. Henry IV., who had noticed his writings, called him to Paris; and, on his solicitation, caused twenty thousand mulberry trees and a great quantity of silkworms' eggs, of which a distribution was made over the whole of France, to be imported from Italy. From that moment, sericulture was propagated rapidly in the Cévennes, in Provence, in Languedoc, in Touraine, and many other provinces. Mulberry trees were planted at Fontainebleau, in the royal park of Tournelles, and even in the Tuileries, where an Italian lady, named Julle, reared silkworms for Henry IV.
Notwithstanding this great impulse, sericulture dwindled awayon the death of that king. It received a fresh impulse under Colbert, the great minister, who succeeded in creating the spirit of commerce and trade in France. New manufactories were established, and plantations of mulberry trees formed in many of the provinces. All this progress was suddenly brought to a standstill by the iniquitous revocation of the Edict of Nantes, which deprived France of her leading commercial men. Driven from their own country, the Protestant families of the Cévennes established abroad silk manufactories, the fabrics of which rivalled those of French production.
In the eighteenth century the intendants of the provinces tried, but with very slight success, to give a fresh impetus to sericulture in France. The Abbé Boissier de Sauvages published, about 1760, some works, which prove him to have been a patient observer, an accurate reasoner, and a clever rearer of silkworms. Boissier de Sauvages is the father of modern silk-culture. During the first Revolution, men's minds were occupied with graver subjects than the cultivation of the mulberry tree. But, on the return of peace, they got to work again on all sides. In 1808, the minister Chaptal estimated the weight of the cocoon harvest at between five or six thousand kilogrammes; whilst the invention of the Jacquard loom gave an immense impulse to the weaving of silk stuffs. Amongst those who introduced and benefited the art of sericulture, we must not forget Dandolo. Dandolo, who was born at Venice in 1758, and died in 1819, was the first who, at the beginning of this century, applied himself seriously to the amelioration of the processes employed in the cultivation of silk. He endeavoured to regulate the temperature, to introduce more order into the distribution of the food to the worms, to have more spacious premises, and to have these properly ventilated.
Now we are on this subject, we must mention the names of those who at the present day have rendered important services to sericulture—such as M. Camille Beauvais, who raised silkworm rearing from the inactivity into which it had been plunged; M. Eugène Robert, who founded in the south of France the first successful silkworm nursery; M. Guérin-Méneville, who has devoted his life to the study of the same question, and to whom Europe owes the introduction and the acclimatisation of some species which will render us, perhaps, one day very great services; and lastly, M. Robinet, who has elucidated several practical questions in the art of sericulture. In bringing to a close this rapid historical epitome, we will state that France consumes annually 30,000 kilogrammes of silkworms' eggs, each kilogramme being at the present time worth from 300 to 500francs, and even more. The value of manufactured silks represents annually about 8,000,000 francs; and we find by official statistics that France exported in 1863 silk stuffs to the value of 384,000,000 francs. This immense trade shows how much silk is now-a-days everywhere appreciated; in those numerous tissues called taffeta, satin, and velvet, each of which seems to have a charm—a peculiar attraction. The consistency of the stuff, the smoothness, the softness of surface, the manner in which silk receives colours, the brightness, fineness, power of reflecting, the rustling, the light or heavy folds,—all these are beauty, elegance, and luxury, in whatever way these words are understood.
TheBombyx morihas, however, nothing alluring in its appearance. Other caterpillars of the genusBombyxhave brilliant liveries; they are adorned with spots, blue as sapphires, green as emeralds, red as rubies, but produce threads without brightness and fineness. The humble silkworm, in a white blouse, like a workman, has nothing brilliant in its dress, and yet it gives to the whole world its most beautiful and gorgeous array. The body of the silkworm is composed of thirteen distinct segments. In front are three pairs of articulated legs, which will become later those of the moth. In the middle and towards the posterior part, are five pairs of membranous legs, furnished with a circle of very fine bristles, which assist the animal to hook itself on to leaves and stalks. On the two sides of its body are eighteen stigmata, or respiratory mouths.
The head of the silkworm is remarkable; it is scaly, horny, and formed of one single piece. The mouth is provided with six small articulated pieces. Below is a simple blade, the upper lip, having in its middle a hollow, into which the animal causes the edge of the leaf it is gnawing to enter, and holds it thus without any exertion. Underneath the lip are inserted two large jaws, which cut the leaf as a pair of scissors. Underneath, some weaker jaws divide the fragments, and a little organ, articulated on to each jaw, that is to say, a palpus, pushes them back towards the mouth, and prevents the smallest particle of the leaf from falling. And lastly, in the space comprised between the two jaws, is an under-lip, which completely closes the mouth below. At the extremity of this piece may be seen a little prolongation, a sort of papilla, pierced with a hole, which is the orifice that gives issue to the silky thread.
The organs which serve for the elaboration and emission of the silk have a peculiar interest for us. If we dissect a silkworm under water, we succeed, sooner or later, after having removed the outer parts, in laying bare a double apparatus, placed along the two sidesof the intestinal canal and below it. This is the apparatus which secretes the silk; it is the double silk-bearing gland. Each one of these glands is composed of a tube formed of three distinct parts (Fig. 201). The part which is nearest to the tail of the worm is a bent tube,A B C, of a thirtieth of an inch in diameter, and about nine inches in length, twisted a great many times into irregular zig-zags. This part of the silk-producing organ is continued in an enlarged portion,D E, which is the reservoir of the silky matter. To the extremity,E, of this reservoir, is attached another capillary tube,E F. These two capillary tubes, proceeding from the two glands, unite together like two venous trunks, as the plate shows, in one single, short canal,F, which opens in the mouth of the worm, at its under-lip.
Fig. 201.Silk secreting apparatus.
It is in the narrow hinder tubes that the silky matter is formed. It collects in the swollen part,D E, which is, properly speaking, the reservoir; and remains there in the glutinous state. Having reached the capillary tubes, it begins to assume consistency, and forms two threads, which are united together at the point of junction of the tubes, and come out through the orifice, with the appearance of a single thread, to be conducted and directed by the animal to those points it has selected.
It was hoped that by taking from the body of the worm the viscous matter contained in the glands, silk could be formed. But this hope was disappointed. It was found possible, it is true, to take the silk out; to draw it out into threads more or less fine; but up to this time it has only been possible in this way to obtain a matter which, when dried, more or less resembles catgut, and is easily enough spoilt by water.
The viscous substance contained in the glands must then be elaborated by the insect itself. When it arrives in the conduit common to the capillary tubes, under the form of a thread, it is impregnated with a sort of varnish, which is poured into them from two neighbouring glands. The varnish unites the two threads into one single thread, and imparts to it the brilliancy of silk, and the property of resisting the action of water. It is during the last phases of the worm's development that the silky matter becomes abundant in theglands. At this period the animal eats much; and it is certain that the substance to be converted is furnished by the leaf of the tree on which the insect feeds.
In consequence of this having been remarked, some manufacturers have attempted to obtain their silk directly from the mulberry leaf; but they only get a bad floss or refuse silk. This is because the silk is not formed in the mulberry leaf. The organs of insects are laboratories, in which manipulations unknown to man are carried on, manipulations which he has not been able to imitate.
After this rapid glance at the fundamental parts of the organism of the silkworm, we will occupy ourselves with the natural history, properly so called, of this insect, and with its rearing, carried on with a view to the production of silk.
As belonging to the first part of this programme, we have to speak of themoult, of theagesof the silkworm, of its maturity, of itsmountingorascending season, of the formation of the cocoon, of the chrysalis, of the moth, and the eggs.
The name moult has been given to a sort of crisis during which the renewing of the skin of larvæ takes place. When it approaches, the silkworm changes its colour. Its robe, which was white or grey, and opaque, becomes yellow and somewhat transparent. The head swells considerably, especially above, and the skin becomes wrinkled (Fig. 202). The worm then fasts, and prepares to cast its skin. It places here and there some silk threads on the surrounding objects. It then slips under these threads, so that during its movements the old skin which it will abandon is, so to speak, gathered up. It then assumes a peculiar position, that represented inFig. 203, and remains in it in a state of immobility which has been called sleep (sommeil).
During this sleep the new skin is formed under the old. A liquid oozes forth between the two membranes which separates them, and allows the silkworm to leave its old skin. To effect this, the worm begins by raising its head, and by making contortions. The old skin splits round the muzzle, or snout, on the head and back; then bydifferent movements the animal emerges from its skin, which remains held up by the silken threads. The duration of the time occupied in moulting varies with the degree of the heat or humidity of the atmosphere; but in general the state ofsleeplasts from twelve to twenty-four hours. One hour after the crisis the worm begins again to eat.
Fig. 204.Egg and firstage.
Theagesof the silkworm are the periods of time which elapse between one moult and another. If we observe some silkworms when the temperature is favourable, we shall find that there are four moults, and consequently five ages. At the first age (Fig. 204), the silkworm is black and hairy; then of a nut colour at the moment when the first moult is going to take place. "The appearance presented by these worms collected together on a leaf," says Dandolo, "is that of a downy surface of a dark chestnut colour, in the midst of which one sees nothing but a movement of little animals having their heads raised, working them about, and presenting black, shiny muzzles. Their bodies are completely covered with hairs arranged in straight lines, between which one perceives along the whole length of the body other longer hairs."[60]
The first age lasts for five days. At the second (Fig. 205), the worm is grey, almost without down, then of a yellowish white, and one sees the crescents making their appearance on the second and fifth segment. At the third age (Fig. 206), there is not a single hair remaining, and the worm becomes whitish, and is always becoming lighter. The third age lasts six days, as does also the fourth (Fig. 207). At the fifth (Fig. 208), the worm has very nearly reached the end of its career in the caterpillar state, and now is the time of its greatest voracity. This age is the longest; it lasts nine days.
At each of these periods in the life of the silkworm may beremarked a physiological fact to which has been given the name offrèze. When the silkworm has just moulted it eats little, but the time very soon arrives when it does so with extraordinary avidity. It is indeed insatiable. Thefrèzeof the last age is called thegrande frèze. It takes place about the seventh day. During this day worms, the produce of thirty grammes[61]of eggs, consume in weight as much as four horses, and the noise which their little jaws make resembles that of a very heavy shower of rain. It is at the end of this stage that the insect prepares the shelter in which is to be brought about its metamorphosis into a chrysalis.
Fig. 208.—Fifth age.
A little while before this it ceases to eat, turns yellow, and becomes as transparent as a grape. It is now said to have reached itsmaturity. Up to this moment the worm had never tried to leave its litter. It lived a sedentary life, and never thought of wandering away from its food. Now it is seized with an imperious desire for changing its quarters. It gets up, it roams about, and moves its head in all directions to find some place to cling on to. It walks over everything within its reach, particularly over those obstacles which are placed vertically. It aspires, not to descend, like the heroes of classic tragedy, but to rise. It is for this reason that this period of the silkworm's life has received the name of themountingorascending season. It now looks for a convenient place in which to establish its cocoon. Every one has remarked how the animal sets to work to accomplish its task. It begins by throwing from different sides threads destined for fixing the cocoon; this is what we callrefuse silk. The proper space having been circumscribed by this means, the worm begins to unwind its thread—a continuous thread of about a thousand mètres long.
It has been calculated, let us say by the way, that forty thousand cocoons would suffice to surround the earth at the equator with one thread of silk. Folded on itself almost like a horse-shoe, its backwithin, its legs without, the worm arranges its thread all round its body, describing ovals with its head. It approximates gradually the points of attachment of the thread. As long as the cocoon is not very thick one can watch it through the meshes of the web applying and fixing its thread, still to a certain degree soft, in such a manner as to make it adhere closely to the parts already formed.
"We can state," says M. Robinet, "that the silkworm makes every second a movement extending over about five millimètres. The length of the threads being known, it follows that the worm moves its head three hundred thousand times in making its cocoon. If it employs seventy-two hours at its work, it is a hundred thousand movements every twenty-four hours, four thousand one hundred and sixty-six an hour, and sixty-nine a minute, that is to say, a little more than one a second."
About the fourth day, after having expended all its silk,[62]the worm shut up in the cocoon becomes of a waxy white colour, and swollen in the middle of its body. The abdominal legs wither away; the six fore legs approach each other and become black. The parts of the mouth tend downwards; the skin wrinkles. Very soon it is detached and pushed down towards the hinder part, and the chrysalis appears under the rents in the skin. It is at first white, but speedily becomes of a brown red.
The silkworm remains in general from fifteen to seventeen days in the pupa state. At the moment of hatching, the moth begins by breaking the skin in which it is shut up, and which is pretty thin. But how can it come out of the silky prison which it has itself built? To effect this it makes use of a peculiar liquid contained in a little bladder with which its head is provided, and which was discovered by M. Guérin-Méneville. It moistens the cocoon with this liquid; which soaks through and penetrates the whole thickness of the silken wall which confines it. The threads of silk of which it is composed are moistened and disunited, but not broken. The moth opens a passage for itself through the threads thus separated, and makes its appearance in the light of day. Its wings are folded back on themselves, and it is still quite wet, but it seeks immediately for a good place in which to dry itself, and in a little time assumes its final appearance (Figs.209,210). The female (Fig. 210) has whitish wings, the antennæ only slightly developed and pale, the abdomen voluminous, cylindrical, and well filled. It is quiet, heavy, and stationary. The male is smaller; its wings are tinged with grey,its antennæ blackish; it moves about, beats its wings together, and is lively and petulant.
Fig. 253.—Silkworm Moth (Bombyx mori), male.