Silk-Worm, or Phalaena Bombyx Mori, a native of China, where it propagates on the mulberry-tree, the leaves of which serve as its only natural food. From the labours of this valuable insect, we obtain Silk. The worm is hatched from yellowish eggs, the size of which is rather smaller than mustard-seed-, and which are laid by a species of white moth, mbling a butterfly. Raw silk has hitherto been imported into Britain, at a considerable annual expence; though, it appears that England, in particular, possesses certain advantages over the southern climate-, of Europe, for raising silk; and which, if they were properly attended to, promise to be productive of a great saving to the nation. Thus, the eggs may, in this country, be preserved throughout the winter and spring, without an apprehension of being hatched before the mulberry-leaves appear; provided they be kept in cool places, and not exposed to the influence of the sun; whereas, in Tuscany, and other warmer parts of Europe, it is scarcely practicable to keep them in an embryo state, even a few - Cold, thunder, and lightning, are equally destructive to and the countries above mentioned are subject to that endanger their existence ; while Britain is almost from the latter casualties. Nay, incalculable .
i of silk-worms are annually bred in Germany, Prussia, Swe-den, etc. the climates of which
My colder than the Bri-eral: hence, we trust, that the culture of slik will become a source of national profit.
When the egg is hatched, after being exposed to a warm temperature of from 60 to 70° of Fah-RENHeit, for a few days, a small black worm bursts forth, which is very eager for food, and ought to be supplied with the most tender mulberry-leaves. These will be greedily eaten for about eight days, at which period the worm is seized with a lethargic sleep, for three days ; when it changes its skin. The creature now begins to eat again for five or six days, till it becomes subject to a second sickness or sleep, of a similar duration. A third and fourth stages of equal length succeed, so that in about 32, or 36 days, the silk-worm attains its full growth, being in this climate from one to two inches, but, in the warmer countries, from three to four inches in length.
After these four successive revolutions, the insect devours its food with great avidity for five or six days longer; at the end of which it becomes sickly, and in a manner transparent, when it requires no farther nourishment: at this period, it endeavours to find a convenient spot between dry branches, in a dark corner, and begins to spin ; winding the silk which it draws from its bowels, around its own body, in an egg-shaped, roundish ball, denominated a cocoon. In this state, the worm remains for a fortnight, and upwards, inclosed in the centre of its silky habitation, whence it bursts forth in the form of a whitish moth, the wings of which are marked with yellow or brown lines : each female lays from 3 to 500 eggs, within two or three days, when she dies without tasting any food ; and the male generally perishes in 24 hours, after having propagated its species. - It deserves to be remarked, that, during the first day of its labours, the silk-worm spins only the exterior, irregular texture, which is known, in commerce, under the name of floret, or coarse silk, serving lor inferior stockings, gloves, etc. On the second or third day, it begins to manufatture fine, connected filaments, extending several hundred yards in length ; and, after this useful work, the creature completes its task, by forming its oval solid case, that resembles thin parchment, and in which it rests with safety, till it emerges in the shape of a butter-fly. - Those co-coons, however, which are intended for the production of silk, ought to be selected within a week, and exposed to a hot oven, in which bread has been previously baked ; with a view to prevent the worm from cutting the siik : on the contrary, such as are designed for breeding, ought to be carefully selected, namely, one male to each female; the cocoons of the former being somewhat pointed at one end, while those of the latter are generally of a larger size.
Having thus stated the various changes which silk-worms undergo, we shall proceed to point out the most proper vegetables for their subsistence. The best adapted for this purpose, are the leaves of the black and white Mulberry-tree ; and, though we have remarked, vol. iii. p. 241, that this tree did not prosper in Britain, yet we understand from later information, that it may be advantageously cultivated, particularly in Cornwall ; on which account the Board of Agriculture has been induced to recommend the breeding of silkworms to the inhabitants of that county. As, however, mulberry-leaves cannot always be procured in sufficient quantity, the insects, if kept in a warm place, may be occasionally fed with those of lettuces. The young (neither moist nor withered), leaves of blackberries, vines, cowslips, ash, and primroses, have also been advantageously employed for this purpose ; and it is asserted, that elmes may be safely given to them; though some breeders observe, that such food inevitably causes their uction. In the management of silkworms, cleanliness is an object of the. first importance : hence, to facilitate the rearing of these profitable creatures, in this climate, the Rev. Mr. Swayne has contrived an ingenious apparatus, by means of which, large numbers may be bred in a small compass. It con-sists of a wooden frame, 4 feet 2 inches in height 5 each side being 16 1/2 inches wide, and divided into eight partitions, by means of small wooden grooves, into which are introduced sliders, that may thus be drawn in, or out, at pleasure. The upper slider is of paper, and is destined for the reception of the worms, as soon as the eggs are hatched. The two next are formed of cat-gut, the threads of which are about one-tenth of an inch asunder ; and are designed for them, when somewhat increased in size. The five lower sliders are constructed of wicker-work, with openings about a quarter of an inch square, through which the dung descends. Beneath all these are placed paper-sliders, to prevent the excrements from falling on those which are beneath them. - For a more detailed account of this contrivance, the reader is referred to the 7th volume of the " Transactions of the Society for the Encouragement of Arts, " etc. where it is fully described, and illustrated with an engraving.
For the successful rearing of silk-worms, two essential objects ought to be attended to : 1. A sufficient plantation of mulberry-trees; and 2. A proper stock of eggs for batching, obtained from a climate similar to that in which they are to be bred. Besides, it will be advisable to keep the latter in a cool, but not in a cold place, till the tender mulberry-leaves are secured from the effect of night-frosts. The room in which the insects are managed, should be lofty, dry, and rather dark than too light. In short, they ought to pass through their different stages of life, in an uniformly warm temperature, not exceeding that of summer heat.
The quality of silk greatly depends on the manner, in which the raw threads are manufactured. In order to wind them off the cocoons, they are immersed into hot water for a minute or longer, when they are taken out and reeled by means of a machine ; the threads are next twisted, and at length woven into ribbons, satins, &.c.
Convinced of the great importance of the silk-manufacture to this country, the Society for the Encouragement of Arts, etc. Lave offered various premiums, with a view to promote the production of silk, in Britain. The successful candidates were, 1. Mrs. Williams, who received 20 guineas in 1778, for her attention to this object. - 2. Miss HenRiettaRhoDes, to whom, in 1785, the Society presented their silver medal. - 3. The Rev. Mr. Swayne, who obtained a similar reward in 1789; and lastly, Mr. SalvatoRe BeRte-zen, on whom, in 1790, they bestowed their gold medal.
It would exceed the limits of our plan, to specify the different methods adopted by these patriotic individuals ; and, as we have already selected a few hints, both from their communications, and from foreign authorities, the inquisitive reader will consult the 2d, 4th, 5th, and 7th vols, of the Society's " Transactions, " etc. in which the various expedients practised by silk-cultivators in this country, are fully related. - Some practical remarks likewise occur in Mr. Bertezen's " Thoughts on the different kinds of Food given to Silk-worms" etc. (8vo. pp. 47, is. Rew, 1789); a treatise worthy of perusal.