By the time the worms have attained their full maturity and growth, they have generally denuded of their foliage the whole plantation of mulberry-trees, and the attendants therefore look anxiously for the lime when they shall cease eating; this they do suddenly, and again fall into a state of stupor, which lasts about two days. On again awaking to activity, the silkworm, for the first time since it came into life, shows signs of restlessness, and crawls hastily about in search of a retreat. As soon as this restlessness is perceived, the attendants carry in a quantity of dried twigs and branches, and carefully scatter them over the worms, who take to them with such avidity, that, in the course of an hour or two, not one will be found who has not selected for himself a spot whereon to weave a silken bed.
As soon as the caterpillar has fixed upon a place for the formation of its cocoon, it attaches long threads of glutinous matter or silk from side to side, to form a support for itself, and thus continues to work until it has woven around itself a hollow envelope of light tissue-like texture. As it does not move or change the position of the hinder part of its body, but continues moving its head from side to side, attaching and drawing the thread from point to point, it follows naturally that, after a time, its body becomes enclosed by the network thus produced. The work is then continued from one thread to another, the caterpillar moving its head and spinning in a zigzag manner, bending the forepart of its body back so as to spin in all directions within reach; and the position of the body is only changed for the purpose of covering the part which was beneath it with silk. As the web is thus spun by bending the forepart of the body back, it follows that the silkworm very soon encloses itself in a cocoon very much snorter than its own body, and the work is thus continued with the worm in a bent position. Thus the worm, by pure instinct, forms a cocoon which is of just sufficient size for its purposes in the chrysalis stage, and not guided by its present proportions. During the time of spinning, the silkworm decreases considerably in length, and, by the time it has completed its cocoon, has diminished its size by one-half.
The cocoon consists of three distinct layers of silk ; the first loose and flossy, the second of a closer texture, and the inner coating finer, and glued or gummed closely together and forming a compact surface. After building the cocoon, the silkworm divests itself of its caterpillar garment, and is at once transformed into a chrysalis. In the chrysalis state the animal remains for about a fortnight, during which period the delicate and beautiful limbs of the moth are being formed.
At the end of this period a slight swelling of the chrysalis indicates that a new life is about bursting forth ; a rupture down the back succeeds, and, by degrees, the snowy moth emerges from her horny shell into the hollow silken chamber of the cocoon. There, after fluttering for a few minutes, it emits a fluid which has the power of softening the silk at the pointed end of the cocoon, through which the moth soon afterwards bursts into life and activity. The cocoon takes about five days' incessant and unceasing labour in its formation, and, when finished, is egg-shaped, and about an inch and a-half in length.
It must be borne in mind that the silk composing the cocoon is spun out by the animal in one continuous thread, from the first commencement to the completion of the fine lining; the length of this thread of course varies in some small degree, but generally the continuous unbroken thread produced and spun by each worm is about one thousand feet. Of course, as the value and use of the silk depends upon its perfect length being preserved, it would be very prejudicial to allow the moth to be formed in those cocoons which are intended for use. A sufficient quantity having been set aside for producing eggs for the next season, the rest are either exposed to the broiling sun, or placed in a furnace until the poor little animal is stifled in the very beautiful edifice which his ingenuity has formed, and which is so soon converted into a tomb. This done, the grower opens the soft external covering of floss-silk, and removes the harder cocoon. This floss-silk is afterwards brought to a manufactured state by spinning.
The cocoons are now formed into hanks ready for use by the manufacturer. For this purpose small furnaces are raised, adapted to the purpose, on the top of which is placed a vessel of water. Into this water a number of the cocoons are thrown, and the heat of the water soon softens the gum or glue, and renders the separation and proper winding the delicate threads a matter of easy accomplishment. The reeler is provided with a whisk of fine twigs bound together and cut off evenly at the ends, and with this she gently stirs and presses the cocoons in the water till the loose threads become entangled on its points. She then raises the whisk with the threads attached, removes them from it, and draws their ends through her fingers. The operator collects ten, fifteen, or twenty threads together, and passes them through small loops or eyes in a reeling machine. This apparatus is very simple, consisting only of a hollow wheel, upon which she attaches the ends of the threads, while another female turns the handle. By this means fifteen or twenty cocoons are unwound at one time, and as each is drawn off another is substituted, and thus a continuous thread, composed of many cocoons, is produced.
To give a more clear insight into the wonderful capacity of the silkworm for the operations it has to perform, we place before the reader engravings of the animal and its transformations, referring to our previous remarks for the explanations how these changes are effected. In the annexed illustrations we have - A, the female silkworm moth; B, the male moth ; C, the eggs; D, the pupa removed from the cocoon ; E, the caterpillar; F, position of the silk bags and spinnaret in the worm; and G, the cocoon.