The Insect World: Being a Popular Account of the Orders of Insects

After the muscai^dine, we must mention another epidemic disease still more terrible, the gattine. This disease shows itself from the very beginning of the rearing, and increases in intensity at each age, so that the number of worms able to enter regularly into the moult

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becomes smaller and smaller. We are still in a state of utter ignorance as to the cause of this last affection, which has occasioned, at various periods, incalculable losses in the rearing-houses, which threatens the silkworm with complete destruction, and which threatened to ruin the unfortunate countries of the Cevennes, the principal seat of sericulture in France.

During the fifth age, the worms become large so quickly that on the fifth or sixth day they are obliged to be moved away from each other on the litter. The dtliteinent must be made every two days, or indeed, every day now, on account of the enormous amount of the excrement; and, at the same time, a good ventilation must be constantly maintained. The temperature of the room should now be kept to 24^^, without ever exceeding this degree of heat. When it is

Fig. 213. — Sprigs of heather arranged so that Silkworms may mount into them.

perceived that the worms wish to ascend, or vioiint^ there are placed on the tables, at certain distances from each other, little sprigs of heather or very dry branches of light wood.

When the worms begin to mount into the heather, one must encabajier — that is to say, form with these branches little hedges, curved back like a hut or cradle, the openings of which are, on an average, seventeen inches or so (Fig. 213). At the expiration of twenty-four hours all the good worms have mounted. The laggards who remain under the cabcvies are taken off by hand, and placed on a table, which is vmxxx^^x^i^Xy cncabanca.

The cocoons spun on these branches of heather ought to be large, heavy, and well-shaped. The good cocoons are regular; their ends are rounded and not pierced; and they are hard, especially at their extremities, and have a fine grain (Fig. 214). They are cylindrical. The best are drawn in towards the middle, or have a concavity on either side of it (Fig. 215). Every one knows that there are white and yellow cocoons, the produce of different races of worms.

LEPIDOPTERA.

Commerce recognises two kinds of white silk: theyfrj-/ white and the second white. The silk of the first white is produced by the race Sina, the cocoons of which are of a perfect and azured white. They produce the most beautiful and most precious silk, and serve for the fabrication of light and delicate-coloured tissues. The silk of the secotid white is furnished by two races: the Espagnolet and the Roquemaiire.

The races that produce yellow cocoons are more numerous than the white ones. The yellow races are divided into three groups:

"^w^y

Fig. 214. — Spherical cocoon Fig. 215. — Cocoon of Bombyx mori, of the Bombyx mori. drawn in towards the middle.

those that have small, middle-sized, or large cocoons. The first and second are stronger, and more esteemed than the last.

The greater number of the races of silkworms have, let us here mention, white and yellow cocoons; there are some, however, whose cocoons are of a greenish white, or even quite green, or of a reddish green. One race, raised in Tu-scany, near Pistoja, has cocoons of a pale rose colour; and, lastly, mention has been made of cocoons of a purple colour. When the cocoons are completed, the people in charge of the rearing- establishments separate them from the heather and sell them to the silk-spinners. But they must manage to get these cocoons into a state in which they will remain entire during a long time. They must, in other words, kill the chrysalis, to prevent the cocoons being pierced by the moth. To kill the chrysalis so as to prevent the

Fig. 2i6.— Larva, pupa, cocoon, and moth of Bombyx mori.

development of the Imago is an operation which is called the etouffage, or stifling. To effect this stifling, the cocoons are exposed to a high temperature. Formerly, in the C^vennes, the cocoons were placed m a

LEPIDOPTRRA.

baker's oven, heated for baking bread. But they ran -the risk thus of l)eing burnt, or of a certain number of chrysahdes remaining' aUve. Now, to kill the chrysalides, they use steam at too°, produced by water boihng in a vessel, and passing through wicker baskets filled with cocoons (Fig. 217).

The rearer must also take care at the time he gathers them,,to separate the cocoons which are to provide eggs for the next year. As the female cocoons are heavier than the male cocoons, they are easily separated by weighing them in a pair of scales. To obtain the, eggs, or grain, the cocoons are fixed on sheets of brown paper, covered with a slight coating of paste made of flour. They are arranged in such a manner that the moths shall find no obstacle when they come out of them, head foremost; and, moreover, so that they may be able to reach with their legs the cocoon which is opposite them, so as to hang on to it, and to facilitate their exit from their own cocoon (Fig. 218). The male and female cocoons are pasted on separate Fig. 217. Apparatusin the forcocoons.stifling the chrysalides sheets. It is from fifteen to twenty days after the montce^ or mounting, and when the temperature of the rooms has been kept between 20*^ and 25^, that the moths begin to be hatched. As they appear, they are seized by the wings and placed^ on cloths stretched out for the purpose, where they are left for about an hour, till their wings have fallen flat on their bodies. As soon as they have evacuated a red liquor, the males and females, which up to that time have been apart, are put together. They then stick sheets of paper on to screens, putting from twenty-five to thirty females on each sheet (Fig. 219). It is here the moths lay their eggs. The sheets of paper, covered with eggs, are then hung on wires, at a small distance from the ceiling of a room

having a northern aspect, which is never warmed. They remain thus, exposed to all variations of temperatrure, till the return of the warm weather. We will

piifnpW! riiiiiiiiiiiniii!iiiii!!iP"'''^"'MliiWBiiifiii F|i|[|«friPW!r|^^ ^^y ^ '^^^^'Tt^o an^end^ on the windmg of cocoons and the spinning of silk. The winding of co-miUMuiuMinxL coons is an operation which at first sight ap-

CillliiijLUiOJiittt) I pears very simple, but M'hich is in reality a diffi- cittjUiiiittfiiaia] itiMiiittttaxiitiij It requirescult and delicateunremittingprocess.

CiitiiMitiittxlti^,^^^^^ attention, great experi-

I, ence, and a delicacy of touch which can only be

Fig. 218.— Sheet of p;iper with rows of cocoons prepared for found in the fingers of the exit of the moths destined for laying eggs. woman, or rather, in the fingers of certain women. The woman who is spmning, stands before a sort of loom which is called /our (Fig. 220). Under her hand is a copper containing water, which she heats to the required degree by opening the tap of a tube, which brings a current of steam. She plunges the cocoons into the hot water, and moves them about in it, to soften the gummy substance which sticks the silken threads of the cocoon together. Then she beats them, with a light hand, with a small birch-broom. The threads of the cocoons

Fig. 219. — Sheets of paper stuck into screens, and incHned for the reception of moths. get caughttremities of thein twigsthe ex-of which the little broom is made, and the workwoman seizes with her fingers the bundle of threads, and shakes them about till she perceives that thoy arc all single, and in a tit state to be joined together.

Fig. 220.—Silk-winding Establishment.

Let us suppose that it is wished now to make up a b?-in, or staple, by uniting together the ends of five cocoons. She chooses five ends in the mass, makes of these a bundle, and introduces it into the hole of 2.filiere. She makes two staples {brifis) at once, one on her right, the other on her left hand. She then brings them together, she crosses them, rolls them, and twists them, the one on the other, several times; after which, she separates them from above and keeps them well apart, making each of them pass into a hook at a distance, i^from which they are going to twist round into a hank, separately, on jta wheel. The two threads thus twisted are drawn close together, com])ressed, and become one, getting round by rolling on each other, and being kept in continual motion, drawn out as they are by the rapid motion of the wheel.

The difficulty which the emptying the cocoon of its silk thread I jj-presents, makes us understand what difficulties those manufacturers ' '"'must have met with who have lately attempted to extract from the stalks of mulberry leaves a sort of silk. We will enter into no details of the attempts which have been made to accomplish this object in our time, attempts which have, however, been crowned with no success whatever. We will confine ourselves to reminding the reader that these attempts are far from being of recent origination, since they date as far back as to Olivier de Serres, the father of French sericulture. In a little work published by Olivier de Serres, in 1603, under the title of Cueillette de la Soie, " The Gathering of Silk," we find a memoir entitled: La seconde richesse du juurier, qui se trouve en son escora\ pour en /aire des ioilcs de ioute sorte, non moifis utile que la sole proveuaut d'iaiui, " The seco'.id v»'calth of the mulberry tree which is found in its bark, how to make of it cloth of all sorts, not less useful

than the silk derived from this tree." Olivier de Serres proves in this memoir that the second bark, or liber^ of the mulberry tree contains a fibre capable of replacing hemp or flax, and he describes the processes by which this may be obtained. The processes which had been proposed by Olivier de Serres in 1603, were resumed in the

Ce'vennes several years ago by M. Duponchel on the one hand, and on the other by M. Cabanis,"^ who operated on die bark instead of taking the whole of the wood of the mulberry tree. But none of these attempts gave any good results.