SILKWORMS.
“The proudest king
May thank the silkworm for his robe of state.”—Akenside.
The rearing and management of silkworms is an innocent and agreeable pastime both to boys and girls, and it is very interesting in many points of view. One fact is, that while the caterpillars of all the other tribes of moths and butterflies, when they have arrived at a certain state of maturity, show a restless disposition, and wander about and hide themselves in a variety of places in order to spin their cocoons, the silkworm, on the contrary, is content to remain stationary in the open tray or box in which it may be placed. After consuming its immediate supply of mulberry leaves, it waits for a further quantity, and when the period arrives for spinning its cocoon, instead of showing any migratory disposition, it seems to place itself with confidence under the care of man to provide it with a suitable place for its convenience and protection.
The silkworm is systematically known under the name of the Bombyx Mori of Linnæus, or the Mulberry-tree Moth, which in the winged state is of a cream colour, with several transparent bands of a darker colour across the anterior wings and a crescent-shaped central mark. The caterpillar when full grown is nearly three inches in length, and is too well known to our young friends to need any particular description. The eggs when good are of a pale slate or dark lilac colour; they may be purchased in Covent Garden market for about ten shillings per ounce; and care should be taken to obtain them of a proper colour, because those that are of a pale yellow are imperfect.
The silkworm when first hatched is black, and does not exceed in length one-fourth of an inch. The desire for food is the first symptom it exhibits of life, and at this period it is more active than at any other. When about eight days have elapsed after its hatching, its head becomes considerably enlarged, and it turns sick, refuses food, and remains in a state of lethargy for about three days. This sickness would appear to arise from the pressure of the animal’s skin, which has become too tight for the increased bulk of its body. Indeed, the very great difference in the size of the worm from the beginning to the end of the caterpillar state is so great, that Nature has furnished it with several skins, each of which it casts in succession.
The body of the caterpillar is begirt by twelve rings, which approach to or recede from each other according to its motion; there are nine breathing-holes on each side of the body, seven eyes on each side of the head, and two small orifices below the jaws, through which the worm ejects its silken filament.
The art of using this filamentous substance seems to have originated with the Chinese, and to have been discovered at a very early period, and the raw material was purchased by the Persians, Tyrians, and Indians for a long time before it was introduced into Europe. For many ages silk bore an enormous price at Rome, but about the middle of the sixth century two monks arrived at Constantinople from India, bringing with them the white mulberry and the eggs of the silkworm, which have since been reared in Italy, Spain, France, and other parts of Europe.
FOOD OF THE SILKWORM.
The silkworm feeds, as every one knows, on the leaves of the white mulberry; or, when these cannot be obtained, upon those of the black mulberry; or, in lieu of these, upon the leaves of the common garden lettuce. The white mulberry is especially cultivated for the value of its leaves, its fruit being insipid and very inferior to that of the common species, the leaves of which are equally good in this country for the food of the silkworm. There has been a variety lately introduced from the Philippine Isles (Morus multicaulis), which has larger leaves, and which is easily propagated by cuttings put into a cucumber frame in October, and transplanted in the following May; yet, still, to ensure success in the rearing of silkworms the young naturalist should stick to the old black mulberry, as such trees are to be found in various vicinities. To propagate this, a branch from another tree may be set in the earth, which will frequently grow. The amiable Sir John Philipport of Hammersmith, so celebrated for his “Elysian groves and fountains fair,” and for his sterling English qualities, has in his grounds a fine mulberry-tree, which he reared by placing a very loose branch in the ground in the autumn of 1850, which threw out roots, and started at once into a tree. The story of a gate-post made of a mulberry trunk becoming, and now remaining, a fruitful tree, is well authenticated. The leaves to be used should be those of a large and well-grown, prolific tree, and they should be gathered with care, so that the young buds of future leaves should in no way be injured; moreover, a tree should never be stripped twice in a year.
HATCHING, FEEDING, AND TEMPERATURE.
Having procured the eggs, which should be obtained about the latter end of April—they are generally bought on slips of paper just as they were laid by the moth—they should be placed in trays made of stout cartridge or thin pasteboard of the form seen in the cut, and there should be provided to go over the case some thin gauze. The trays may be placed in a window facing the south, where they are fully exposed to the rays of the sun; there they should remain undisturbed till they begin to hatch; and as the young worms appear they should be removed into other trays, and fed with the mulberry leaves. The temperature should be regulated from sixty-six to seventy degrees, and the room ventilated, and preserved equally free from damp or too much dryness. They should be kept particularly clean, dead leaves and dung cleared carefully away, and in lifting them from one tray to another they should not be touched by the fingers, but removed by threads of cotton passed under their bodies, or with a camel’s-hair pencil.
MOULTINGS.
The caterpillar has four moultings, which may be all accomplished in the period of four days each, if the heat of the room be increased to from ninety-five to one hundred degrees of Fahrenheit. When the heat is regulated to a lower standard, the first moulting takes place on the fourth or fifth day after hatching, the second in four days more, the third in five or six days more, and the last in about eight days. Ten days more are required after this moulting, so that in about thirty-two days after hatching the caterpillar has attained its full size. During all these changes of the worm it requires the nicest attention.
THE COCOON.
At the end of the time mentioned above the worms change to a clear pink or flesh colour, and look semi-transparent; they refuse their food, become restless, and prepare to spin or form their cocoon. At this time care should be taken to raise the walls of their tray habitation, or they will climb over them and be lost. What is called the cocoon nest should now be prepared by twisting the corners of a piece of writing-paper, and raising its edges into the form of the lower shell of an oyster. A number of these should be prepared and affixed to a piece of tape, with their pointed ends downwards; and into each one a single worm should be placed when it quits its food, and seems ready to spin: it will then dispose its web in such a manner as to leave a cavity within.
The cocoon consists of three distinct layers of silk: the first is loose and flossy, and is unserviceable for the silk manufacture; the second is closer, the silk crossing from side to side; and the third is still finer, and is glued strongly together, so as to form a compact inner coating.
THE AURELIA.
When the cocoon is completed, the enclosed caterpillar again casts its skin, with the head and jaws attached to it, when it appears under the form of a conical chrysalis of the ordinary shape. At first the chrysalis, when opened, exhibits only a yellowish fluid, but by degrees the various parts of the future moth appear, and in about a fortnight or three weeks a slight swelling of the chrysalis indicates the approach of another change; a rupture down its back succeeds, and by degrees the moth bursts through its horny coating into the hollow chamber of the cocoon, and if left to itself would soon eat its way out.
WINDING THE SILK.
The chrysalis, however, must be prevented from eating through the cocoon; and previous to the egress of the moth from its aurelian state, the silk must be wound off. When, by taking up the cocoon, it is found that the caterpillar has passed into the aurelian state—which may easily be known by shaking it, as then the aurelia, from its harder texture and shrunken size, will be heard to rattle—then it is time to wind off the silk. The cocoon is placed in a cup of warm water, after the loose outward silk has been removed, and then, an end being taken, the whole continuous filament may be wound off on a piece of card. The length of the thread of a cocoon varies from 600 to 1,000 feet; yet the whole does not weigh more than three grains and a half. An ounce of eggs will produce about 40,000 caterpillars, which will consume 1,073 lbs. of leaves, and produce from 80 lbs. to 100 lbs. of cocoon, or about eight pounds of raw silk.
THE MOTH.
When the silk is wound off the aurelia presents itself, and being put in a separate case, it remains motionless for about twenty days, when suddenly it appears as a pale yellow moth, with wings which seem scarcely adapted for flight. It crawls heavily about the place where it has been hatched, having a slight tremor in its wings, and eats nothing: the male speedily dies; the females hover about a while without flying, and lay their eggs on the slips of paper presented to them for that purpose. They then soon perish. The female moth generally produces about 300 or 400 eggs.
THE MOTH.
GENERAL REMARKS.
The place where silkworms are bred, should persons wish to pursue their rearing upon a larger scale, must be free from noisome smells, cattle, and all noises. Persons attending them must be scrupulously clean in their persons, and wash themselves after every meal. Great attention must also be paid to the temperature of the apartment in which they are kept, which must also be free from all dust or smoke; and the most thoughtful and tender care is requisite in everything connected with their treatment and management.
