Page images
PDF
EPUB

The male cocoons differ from the female by their shape and size. The former are smaller than the latter, and present a cavity upon their back. The latter are larger, presenting the figure of an olive or the egg of a small bird.

The color of these cocoons ought to be of a golden yellow after collecting, and should exhibit no spot or stain of any kind.

In the same breed, the heaviest cocoons are in general those which offer the greatest chance of affording the best reproductions. Then, after having put a certain number of male cocoons on one side and of female on the other, weigh both parts to find the average weight of each, and every time that this average weight is exceeded there is a presumption that excellent cocoons are obtained for reproduction, all other things being equal.

[ocr errors]

It is, however, necessary to remark that, as one part of the cocoons contains sometimes the same gross measurement, it should not be confounded with the normal cocoons. Cocoons of an exceptional bulk are in general the result of two grubs united under the same envelope. Their product is known under the name of "doubles," or "douppions," or twin threads.

This sort of product is always inferior, as much because the beds or envelopes are almost invisible, as because the association in the work indicates a weakness in the subject.

Notwithstanding all the attention and care given by the breeder to prevent the production of doubles, and sometimes even of triples, he must inevitably expect to find a certain proportion of those, the value of which is hardly one-third the price of the normal product.

There was exhibited in the Exposition an apparatus contrived by an Italian silk husbandman, designed to prevent these douppions in the breeding of worms.

The apparatus consists in an arrangement of cells made of very light wood, each one of which has only the bulk necessary for a single grub. When these come to their full development, ready to spin their cocoon or boll, instead of preparing heath, shrubs, or other kinds of shelter or supports against which the worms are to spin, this kind of cells is supplied where each insect has its own separate case, which prevents two or any greater number from uniting to make a defective product.

The Italian exhibitor is endeavoring to bring into general use this system of isolation or cellular breeding.

The system presents, according to the inventor, other advantages, by the facility which it offers in the choice of the best reproducers, and by preventing the coupling between grubs of the same family, consanguinity having been considered as one cause of the rapid deterioration of the breed.

When the coupling has been accomplished, the females are removed and made to lay, each in the cell reserved for her, in such a way as to be able to weigh separately the eggs of each laying.

This weight is not to be inferior to a certain ascertained proportion, for the eggs would then be evidently bad. In order that they may offer good chances of success, each laying should weigh at least 60 or 70 grams, (per kilogram of cocoons,) each gram to contain 1,350 to 1,500 eggs on an average.

THE SILK-WORM AND ITS VARIETIES.

THE COMMON SILK-WORM, (Bombyx Mori.)

The common silk-worm and the species mostly in use, and which produces by far the best silk, is born in the spring, ordinarily about the middle of May. It feeds on the leaves of the mulberry tree and attains its full growth in about six weeks.

During that period it changes its skin four times, and according to M. de Quatrefages, of the French Institute, increases its weight 72,000 times. Early in July, having reached its full development, it establishes the workshop of its wonderful manufacture.

Placed in a comfortable and secure position, it proceeds to envelop itself in a cocoon formed by a filament of exceedingly fine silk, emitted from the stomach of the insect. It soon disappears in the centre of the cocoon or silken envelope, and, after about 72 hours of unremitting labor, produces a thread ordinarily not less than 1,600 yards in length.

In that chosen retreat the silk-worm again sheds its skin, for the fifth time, but the insect which comes out is no longer a silk-worm, but a chrysalis-bearing but slight resemblance to the worm. After two weeks or more, according to the temperature, the skin of the chrysalis opens, and, changing for the last time, it becomes a butterfly, lays some hundreds of eggs, and dies.

Besides the Bombyx Mori, there are other species of silk-worms that merit a brief notice, and particularly the following:

CASTOR-OIL PLANT SILK-WORM, (Bombyx Arrindia.)

This species of silk-worm is a native of Bengal and of British India. It lives, both in its wild and its domesticated condition, upon common castor-oil plants and other vegetation. It was but lately introduced into Europe by means of a few living cocoons imported into Malta. Their propagation was not only successful, but was continued in Italy, whence many were sent to France and the Canary islands.

Wherever the castor-oil plant grows spontaneously, as in Algiers, Brazil and Rio de la Plata, the efforts to raise this species of silk-worm have been crowned with success. Its cocoons cannot be reeled in the ordinary way, but they furnish a staple which, when spun into threads, produces fabrics of good suppleness and durability, though almost destitute of lustre.

AILANTHUS SILK-WORM, (Bombyx Cynthia Vera.)

This kind of worm is indigenous to the temperate regions of China, where it lives mainly on the ailanthus. It has long been cultivated by the Chinese in the open air, and produced an elongated cocoon of a red. dish shade, furnishing a kind of bourre de soie, from which is made a very strong and durable tissue.

This silk-worm was introduced into Europe for the first time in 1857, and into France in 1858, where the first successful rearing of it is chiefly due to Madame Drouyn de Lhuys.

But it is to M. Guerin Ménéville, who, under the patronage of the Emperor, experimented extensively and with success, that belongs the credit of having given to this silk its growing importance and industrial value.

THE TUSSEH SILK-WORM, (Bombyx Milita.)

This notable insect lives in a wild state in Bengal, and in the hot regions of India, in the woods, where the inhabitants go to gather the cocoons, which are remarkable for their size and form. Its favorite food is the leaves of the jujube tree. Efforts have been made repeatedly to reproduce it in France, but in vain. The cocoons of this insect produce a fine and brilliant silk, and very strong, known in India as Tusseh, of which large quantities are exported to Europe.

THE WILD SILK-WORM OF JAPAN, (Bombyx Yama May.)

This worm, raised from eggs sent from Japan by the consul-general of France at Yeddo, has been successfully reared. The oak leaf and trees of the same kind are its only nourishment. It does not require great heat, and is easy to raise. Its cocoon, of a greenish yellow, is formed like that of the ordinary silk-worm, and can be reeled into a beautiful silk.

BOMBYX CECROPIA.

This description of worms, indigenous to the temperate regions of North America, is found principally in the Carolinas, Louisiana and Virginia.

In its uncultivated state it lives upon the elm, the willow, and other trees. It produces a large cocoon of a loose texture and coarse silk.

At the Exposition there was a collection of silk-worms in their different stages. A quantity of eggs, of mulberry leaves, and all that relates to the rearing of the silk-worm, were also displayed there.

The silk-worm is tender and delicate. The experiences of the last twenty years have proven that it is liable to epidemics, that rage with peculiar violence and fatality.

THE SILK-WORM MALADY AND THE REMEDIES PROPOSED.

During the period in which the disease in question has attacked the silk-worms, great research and the most minute study have been made to ascertain the cause.

Some have ascribed this calamity to the mulberry; others have compared it to a species of Asiatic cholera, or an epidemic analagous to the cattle distemper from which England and Germany have suffered so much within the last few years.

Others have asserted that the breeder had gradually departed from and neglected those healthful traditions and maxims so essential to be observed in the breeding and rearing of such delicate creatures.

The breeder, perceiving that he could abridge the period of rearing by raising the temperature of the nursery, prematurely matured unhealthy broods, and thence there arose numerous accidents, because by raising the temperature the appetite was forced, which caused derangements in the animal economy.

These different causes, more or less vague and indeterminate, may have contributed to the development of the epidemic. However, the theory of disease in the mulberry is hardly admissible, considering that it has been demonstrated that worms of different breeds or races, nourished by the leaves of the same tree, have experienced different fates. Some succeeded, the others were attacked by the disease and perished; therefore the food in these cases was innocent of the effect.

In the difficulties by which we find ourselves involved in endeavoring to determine the cause of the malady, we have only to seek out the character and seat of the evil, to be able a priori to reject infected subjects.

After numerous investigations by eminent men, certain spots or bodies of peculiar form and appearance were discovered, with the aid of the microscope, in the very tissues of the diseased worms at the bottom of their digestive canal, evidently foreign to their organization, and in quantities proportionate to the violence of the disease. To these little spots or bodies the name of corpuscules was given. They are oval, transparent, smaller than the globules of the human blood, and resemble the globules of certain fermentations.

Widely different theories prevail in regard to these corpuscules and the remedies required for their eradication. The distinguished savant M. Pasteur has come to the conclusion that it is an organic, constitutional affection of the insect, to destroy which either a specific remedy must be found, or else all the conditions favorable to the production of the corpuscules must be avoided, either by obtaining eggs from countries exempt from the malady, or by allowing none but healthy insects to propagate. He has demonstrated that contact between healthy and infected worms does not impart the disease; while, on the other hand, the absorption of a few corpuscules by feeding upon leaves washed with corpusculous water causes the epidemic to spread with incredible rapidity.

M. Pasteur is of the opinion that search must be made for the corpuscules in the chrysalis, and he developes a very ingenious method for facilitating the discovery.

He recommends the immediate destruction of all insects known to be infected, and the separation from them of the healthy ones, and enjoins the utmost cleanliness as an essential condition for the extirpation of the disease in a silk nursery.

M. Béchamp, who has devoted great patience to the investigation, propounds the theory that the disease is parasitic, and that the parasite is of a vegetable nature of the order of fermentations, and that remedies like creosote will arrest if not destroy the development of these vegetable corpuscules.

His mode of application is to wash the eggs in a solution of creosote, or diffuse an impregnating vapor through the rooms of the silk-worm nursery. Suffice it to say, that the methods recommended by each of these gentlemen for the extermination of the disease have been tried, but with only partial success; but all concur in the opinion that the eggs of diseased subjects are unfit for use, and should be rejected.

It has been demonstrated also that the grubs, the chrysalides, and the moths proceeding from the Japanese race or that of the South American states, have been to the present moment free from all trace of corpuscules and all symptoms of the disease.

Practical breeders of the south of France have made very interesting experiments, from which it resulted that the worm when hatched and bred in stables or in sheep folds generally did well.

Comparative experiments prove that the same lot of eggs divided into two parts gave products good in quality and quantity as to the half raised in the atmosphere of a stable, while the grubs of the other part bred under the ordinary conditions generally perished.

These repeated trials appear to demonstrate that the grave nature of the affliction can be modified by the alkalinity of the atmosphere which developes itself in so declared a manner under the conditions of which we have just spoken. It is a species of treatment analogous to that of the water and salt of Vichy and other thermal springs.

BREEDING OF SILK-WORMS.

The industry whose object is the production of cocoons is composed of elements so special and so different from those of manufactures in general as to require that some details be given on the subject, partly agricultural and partly manufacturing.

The basis of the labor of the silk-worm breeder is founded in general on the amount of mulberry leaves consumed. These leaves constitute in this case the raw material.

We will give some figures derived from localities where the population is relatively condensed, such as the south of France and the north of

« ՆախորդըՇարունակել »