mounting or ascending 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 larvae 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 in Fig. 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 aliows the silkworm to leave its old skin. To effect this, the worm begins by raising its head, and by making contortions. The old skin spHts round the muzzle, or snout, on the head and back; then by

Fig. 202. ilkworm during moulting. Positio Fig. 203. ilkworm w Fig. 202. Fig. 203. Head of the Silkworm during moulting. Position ot Silkworm while moulting.

different 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 of sleep lasts from twelve to twenty-four hours. One hour after the crisis the worm begins again to eat. The ages of 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 Fig. 204. collected together on a leaf," says Dandolo, "is that of a ^^^rge/'' 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

Fig. 205. Fig. 206. Fig. 207.

Second age. Third age. Fourth age.

in Straight lines, between which one perceives along the whole length of the body other longer hairs." *

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 silkwonn may be

“L’Art d’élever les Vers à Soie,” par le Comte Dandolo. In 8vo. 2e édition. Lyon, 1825.

remarked a physiological fact to which has been given the name of freze. 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. T\q freze of the last age is called i\Q grande freze. It takes place about the seventh day. During this day worms,

Fig. 208.— Fifth age.

the produce of thirty grammes* 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.

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 its maturity. 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 the moiiutiug or ascending 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 j sides threads destined for fixing the cocoon; this is what we call; refuse silk. The proper space having been circumscribed by this means, the worm begins to unwind its thread — a continuous thread of about a thousand metres 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 back

One gramme = I5'4325 gr. troy.

(Vitliin, 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 millimetres. 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,* 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 skifi. 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 efi"ect this it makes use of a peculiar liquid contained in a Htdc bladder with which its head is provided, and which was discovered by M. Guerin-Meneville. 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 litde time assumes its final appearance (Figs. 209, 210). The female (Fig. 210) has whitish wings, the antennae 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

g5 * ** Manuel «ic I'Educateur du Ver » Soie," p. 37.

its antennae blackish; it moves about, beats its wings together, and is Uvely and petulant. Before laying her eggs, the female looks out for a place suitable for this purpose. When she has found this place, she ejects an egg covered with a viscous liquid, which causes it to adhere to the body upon which it falls. Very soon she lays a second egg by the side of the first, then a third

Fig. 209. — Silkworm Moth (Bomhyx male. by the side of the second, and so on. She very rarely piles them up on each other. The laying lasts about three days; the number of eggs is from 300 to 700 for each female. The.sc eggs are generally tentacular and flattened towards the centre. At the moment at which they are laid they are of a bright yellow. In a week they become brown. The colour changes then to a reddish grey; lastly it becomes of a slaty grey, remaining this colour during the autumn, winter, and a great part of the spring. Then as the temperature rises, the colour of the eggs passes successively through bluish, violet, ashy, and yellowish shades. And, lastly, they become more and more \

whitish every day as the '

Fig. 210. — Silkworm Moth {Bomhyx ntori), female. hatching time approaches. If looked at closely, one remarks a black spot and a brownish crescent extending along the | circumference. ■ The black spot is the head of the worm, which ' closely touches the shell; the crescent is the body, which is already covered with little hairs. ^Vhen it leaves the egg, the silkworm gnaws through the shell on its side, never on its flat surface. When the opening is large enough, it breaks out through it, head foremost, and immediately fixes a thread of silk to any object it can reach, | no doubt in order to prevent itself from falling. Sometimes the opening is too small to allow of the head passing out, ajid the larva

—...fe^

Is forced to come out backwards, that is to say, tail foremost. At times, not being able to get its head free, the poor animal very soon dies of fatigue and hunger.

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