Silk worm

“ The study and development of the various phases through which the silk worm passes, leading up to its production of the actual filament, have been a subject of intense research in many parts of the world for a great number of centuries. The present silk worm is nothing more than a highly specialized product of a long train of artificial cultivation.
Stages of Growth
The cultivated silk worm passes through four changes in its life of two months, i.e., egg, larva, chrysalis (or pupa) , and adult—a cream-white moth which is about one inch in length. ”

“ The Silk-worm in not the only creature that produces [Pg 3] substances of this description, for many other kinds of butterflies and moths do the same; a kind of silk has also been manufactured from the webs of spiders, and as they require less attention than the Silk-worms, the plan might have answered, had it not been for the ravenous appetites of the little spinners, who, when brought together in any quantity very speedily devour each other. Certain shell-fish also produce a kind of silky thread ”

“ Leaving popular superstitious influences out of account, the quality of the silk is first of all affected by the breed of the worms that spin it, then by the quality of the leaves and the mode of feeding. As I have already remarked, the silk-worm is injured by noise, by the presence and especially by the handling of strangers, and by noxious smells. They must be fed, too, at regular hours, and the temperature of the apartment must not be too high. The greatest defect in Chinese silk has been due to the primitive mode of reeling, which the natives adopt. ”

“ The silk-worm increases its size so considerably, and in so short a space of time,—its weight being multiplied many thousand fold in the course of one month,—that if only one skin had been assigned to it, which should serve for its whole caterpillar state, it would with difficulty have distended itself sufficiently to keep pace with the insect’s growth. The economy of nature has therefore admirably provided the embryos of other skins, destined to be successively called into use ”

“ It is a general law for insects; the butterfly of the silk-worm does not escape it. It is even more rigorous for him than for his brethren that we see flying from flower to flower. From the moment of entering the cocoon, the silk-worm takes no nourishment. When it becomes a butterfly, and has assured the perpetuity of the species, its task is accomplished; there is nothing more but to die. ”

“ The pleasure of the present life is like the Indian worm, which, having involved itself in the leaf of the tree and having been satisfied with food, chokes itself in the cocoon of its own thread.—Yates’s Translation.
This writer, whoever he was, appears to have had a correct idea of the manner in which the silk-worm wraps itself in a leaf of the tree, on which it feeds, and spins its tomb within [64] . ”

“ The silk-worm is an animal of such acute and delicate sensations, that too much care cannot be taken to keep its habitation clean, and to refresh it from time to time with pure air. I have seen them languish and die in scores, in consequence of an accidental bad smell. The soiled leaves, and the filth which they necessarily produce, should be carefully shifted every day ”

“ Among the great variety of caterpillars, the descriptions of which are to be found in the records of natural history, the silk-worm occupies a place far above the rest. Not only is our attention called to the examination of its various transformations, by the desire of satisfying our curiosity as entomologists, but our artificial wants incite us likewise to the study of its nature and habits, that we may best and most profitably apply its instinctive industry to our own advantage. ”

“ The silk worm was brought into the south of Europe in the sixth century, whence the insects, being found profitable, gradually spread into Italy and France, in both of which countries the production of silk has long been an important industry. The worms, when properly cared for, do remarkably well in this country, where, in an early day, considerable attention was given to silk culture. In colonial times the government encouraged the industry, and the production was considerable. ”

“ According to this ingenious observer, the silk formed by these insects is equally beautiful, strong, and glossy with that formed by the silk-worm. When first formed, the color of these spiders’ bags is gray, but, [Pg 159] by exposure to the air, they soon acquire a blackish hue. Other spider bags might probably be found of different colors, and affording silk of better quality, but their scarcity would render any experiment with them difficult of accomplishment; for which reason M. Bon confined his attention to the bags of the common sort of the short-legged kind. ”

“ Thus four or five threads of the spider must be brought together to [Pg 162] equal one thread of the silk-worm, and as it is impossible that these should be applied so accurately over each other as not to leave little vacant spaces between them, the light is not equally reflected, and the lustre of the material is consequently inferior to that in which a solid thread is used.
3. A great disadvantage of the spider’s silk is, that it cannot be wound off the ball like that of the silk-worm, but must necessarily be carded. ”

“ Silk is by far the strongest of the textile fabrics, being nearly three times as strong as flax; it consists of the filaments spun by the silk-worm, Phalœna Bombyx Anori. These filaments are always double, proceeding from two holes in the head of the worm, and are united by a sort of varnish which is moist and clammy when the threads proceed from the insect, and causes them to adhere together. The silk-worm in spinning, moves the head backwards and forwards, attaching the threads on alternate sides and all around till it is completely covered in with a ball of silk ”

“ When the caterpillars are full grown, they climb upon twigs placed for them and begin to spin or make the cocoon. The silk comes from two little orifices in the head in the form of a glutinous gum which hardens into a fine elastic fiber. With a motion of the head somewhat like the figure eight, the silk worm throws this thread around the body from head to tail until at last it is entirely enveloped. The body grows smaller and the thread grows finer until at last it has spun out most of the substance of the body and the task is done. ”

“ The Silk-glands of Lepidoptera are of great interest from the physiological point of view, as well as from the fact that they have furnished for many ages one of the most beautiful of the adornments made use of by our own species. The sericteria, or vessels that secrete silk, are of simple structure, and differ greatly in their size in the various forms of the Order; they sometimes become of great length; in the Silk-worm each of the two vessels is nearly five times as long as the body, while in Bombyx yamamai and others, even this is exceeded. ”

“ Anderson informs us, that in Madras the silk-worm goes through all its evolutions in the short space of twenty-two days. It appears, however, that the saving of time, and consequently labor, is the only economy resulting from the acceleration; as the insects consume as much food during their shorter period of life, as is assigned to the longer-lived silk-worms of Europe. ”

“ Before the introduction of the silk-worm into Europe, and as often as its production is mentioned by the Greek and Roman authors, they had not, for several centuries after the use of it became common, any certain knowledge either of the countries to which they were indebted for this favourite article of elegance, or the manner in which it was produced, By some, silk was supposed to be a fine down adhering to the leaves of trees or flowers; others imagined it to be a delicate species of wool or cotton ”

“ Besides the Bombyx mori, the Doctor enumerates the following seven species, formerly unknown:—1. “The wild silk-worm of the central provinces, a moth not larger than the Bombyx mori.” 2. “The Joree silk-worm of Assam, Bombyx religiosæ, which spins a cocoon of a fine filament, with much lustre. It lives upon the pipul tree (Ficus religiosa) , which abounds in India, and ought therefore to be turned to account in breeding this valuable moth.” 3. “Saturnia silhetica, which inhabits the cassia mountains in Silhet and Dacca, where its large cocoons are spun into silk.” ”

“ It costs less to raise silk-worms in Mexico than in Europe, and a far better quality are produced. Mulberry shoots will produce sufficient foliage to maintain silk-worms within three years after planting.
The eggs, while containing the embryo silk-worm, have a dull lavender color, but after discharging the worm they resembled little sugar pills. The worms were about one-sixteenth of an inch long, but the first week of moulting shows them to be half an inch long and the second week one inch. For the third moulting they are placed on perforated paper, through the holes of which the worms crawl. ”

“ Silken garments, and veils interwoven with gold, with which the body of the rich man is encompassed, are a loss to the living, and no gain to the dead.
Here we think it not out of place to introduce the account of the silk-worm by Georgius Pisida, who flourished about A. D. 640, although he lived at Constantinople after the breeding of silk-worms had been introduced there. According to him the silk-worm pines or moulders almost to nothing in its tomb, and then returns to its former shape. ”

“ It is not the happy fortune of many to be able to devote themselves exclusively to the study of nature, unquestionably the most fascinating of human employments; but almost every one may acquire sufficient knowledge to be able to derive a high gratification from beholding the more common operations of animal life. His materials for contemplation are always before him.
[129] Contemplation de la Nature, part ii. ch. 42.
The silk-worm is a species of caterpillar which, like all other insects of the same class, undergoes a variety of changes during the short period of its life ”

“ To dispose of its silk when spinning, it moves its head in all directions, and each movement is about one-sixth of an inch. As we know the length of the thread, we can calculate how many movements are made in disposing of the silk in 72 hours. We find in this way that a silk-worm makes nearly 300,000 motions in 24 hours, or 4,166 an hour, or 69 per minute. You see that our insect yields not in activity to any weaver; but we must add that it is beaten by the marvellous machines that the industry of our day has produced. ”

“ SPIDER'S SILK.
Urged by the increased demand for the threads which the silk-worm yields, many ingenious men have endeavored to turn the cocoons of other insects to account. In search of new fibres to weave into garments, men have dived to the bottom of the sea, to watch the operations of the pinna and the common mussel. Ingenious experimentalists have endeavored to adapt the threads which hold the mussel firmly to the rock, to the purposes of the loom ”

“ The time that elapses while the silk-worm is undergoing its changes, varies according to the warmth of the weather, and the quantity of nourishment with which it is supplied; the Chinese, who are very particular on this head, take the greatest pains to supply the little creature with food, as on this they say depends the quantity of silk which the worm will produce. ”

“ We have seen that the thread of the silk-worm is composed of two filaments united, but the spider’s thread would appear, from the first view of its five spinnerets, to be quintuple, and in some species which have six teats, so many times more. It is not safe, however, in our interpretations of nature to proceed upon conjecture, however plausible, nor to take anything for granted which we have not actually seen ”

“ It is closely allied to the Cynthia or Ailanthus worm, with the same kind of silk and a similar cocoon, and feeds on the castor oil plant.
The diseases of silk worms naturally receive much attention. Like those afflicting mankind, they arise from bad air, resulting from too close confinement, bad food, and other adverse causes. The most fatal and wide-spread disease, and one which since 1854 has threatened the extermination of silk worms in Europe, is the pebrine. It is due to the presence of minute vegetable corpuscles, which attack both the worms and the eggs. ”

“ In several parts of the East Indies, the silk-worm has been introduced, as might have been expected, with complete success; and, in Bengal alone, the factories find employment for upwards of two hundred thousand persons.
THE MANAGEMENT OF THE WORM.
Silk is the production of a species of Moth, called the Phalæna mori or Mulberry moth, and its original locality, as we have already stated, appears to have been China or Persia. The changes that butterflies or moths undergo, having already been described at page 212 of Vol. ”

“ The supply of waste silk is drawn from the following sources: (1) The silkworm, when commencing to spin, emits a dull, lustreless and uneven thread with which it suspends itself to the twigs and leaves of the tree upon which it has been feeding, or to the straws provided for it by attendants in the worm-rearing establishments: this first thread is unreelable, and, moreover, is often mixed with straw, leaves and twigs. (2) The outside layers of the true cocoon are too coarse and uneven for reeling ”

“ Raw silk is imported in quantities from India, China, Italy, &c.
How is the Silk taken from the Worm?
The people who are employed in the care of these insects collect the golden balls from off the mulberry trees, (to the leaves of which the insects glue their silk) and put them into warm water, that the threads may unfasten and wind off more easily; having taken off the coarse woolly part which covers the balls, they take twelve or fourteen threads at a time, and wind them off into skeins. ”