A large variety of materials have been used in their manufacture by different peoples at different times - painted linen and shavings of stained horn by the Egyptians, gold and silver by the Romans, rice-paper by the Chinese, silkworm cocoons in Italy, the plumage of highly coloured birds in South America, wax, small tinted shells, &c. At the beginning of the 8th century the French, who originally learnt the art from the Italians, made great advances in the accuracy of their reproductions, and towards the end of that century the Paris manufacturers enjoyed a world-wide reputation.
Other Hydrophilidae carry their egg-cocoons about with them beneath the abdomen.
It contains breweries, tanneries, sugar, tobacco, cloth, and silk factories, and exports skins, cloth, cocoons, cereals, attar of roses, "dried fruit, &c. Sofia forms the centre of a railway system radiating to Constantinople (300 m.), Belgrade (206 m.) and central Europe, Varna, Rustchuk and the Danube, and Kiustendil near the Macedonian frontier.
The cultivation of silk cocoons, formerly a flourishing industry, has greatly declined in recent years, but efforts are now being made to revive it.
These cocoons, which may often be seen carried between the mandibles of the workers, are the "ants' eggs" prized as food for fish and pheasants.
C. Janet observed that in a nest of Lasius alienus, established by a single female, the first workers emerged from their cocoons on the 102nd day.
These worms lay cocoons like the Oligochaeta and leeches, and where they depart from the structure of the Oligochaeta agree with that of leeches.
The annual average value maybe put at not quite £2,000,000, machinery and tin-plate being a long way the most important items. There is further a small transit trade through Transcaucasia from Persia to the value of less than half a million sterling annually, and chiefly in carpets, cocoons and silk, wool, rice and boxwood; and further a sea-borne trade between Persia and Caucasian.
Several facts point to the conclusion that the primary use of this secretion was the formation of egg-cases or cocoons by the female, for this is the only constant use for which the silk is employed, without exception, by all species.
Other articles of export are silk cocoons, wool, hides, sponges, eggs and fruits (oranges, almonds, raisins and the like); the amounts of cotton, tobacco and wine sent out of the country are small.
The staple silk industry (which dates from the 16th century) has declined, the number both of filande (establishments wherein the cocoons are unwound) and of filatoje (those wherein the silk is spun) having diminished.
The modern town is connected with Smyrna by railway, and exports cotton, wool, opium, cocoons and cereals.
The value of trade probably exceeds 2,000,000, principal exports being rice, raw silk, dry fruit, fish, sheep and cattle, wool and cotton, and cocoons, the principal imports sugar, cotton goods, silkworm "seed" or eggs (70,160 worth in 1906-7), petroleum, glass and china., The trade in dried silkworm cocoons has increased remarkably since 1893, when only 76,150 lb valued at 6475 were exported; during the year 1906-7 ending 10th March, 2,717,540 lb valued at 238,000 were exported.
The larvae of the latter usually vacate their galls, to spin their cocoons in the earth, or, as in the case of Athalia abdominalis, Klg., of the clematis, may emerge from their shelter to feed for some days on the leaves of the gall-bearing plant.
Some of them build cocoons within their galls, others descend to the ground or become pupae.
It has manufactures of cotton, tobacco and leather, and a large trade in wine, silk cocoons and red pepper.
The art of sericulture concerns itself with the rearing of silkworms under artificial or domesticated conditions, their feeding, the formation of cocoons, the securing of these before they are injured and pierced by the moths, and the maturing of a sufficient number of moths to supply eggs for the cultivation of the following year.
Cf seed of 30 grammes producing 30,000 to 35,000 silkworms (30,000 may be depended upon to reach the cocoon stage) will give a harvest of 130 to 140 lb fresh cocoons and an ultimate yield of about 12 lb raw silk properly reeled.
Crowding of positions must now be guarded against, to prevent the spinning of double cocoons (doupions) by two worms spinning together and so interlacing their threads that they can only be reeled for a coarser and inferior thread.
Such cocoons as are selected for the production of graine, on the other hand, are collected, freed from the external floss, and preserved at a temperature of from 66° to 72° F., and after a lapse of from eleven to fifteen days the moths begin to make their appearance.
Partly supported by imported eggs, the production of silk in France was maintained, and in 1853 reached its maximum of 26,000,000 kilos of cocoons, valued at 117,000,000 francs.
From that period, notwithstanding the importation at great cost of foreign graine, reaching in some years to 60,000 kilos, the production of silk fell off with startling rapidity: in 1856 it was not more than 7,500,000 kilos of cocoons; in 1861 and 1862 it fell as low as 5,800,000 kilos; and in 1865 it touched its lowest weight of about 4,000,000 kilos.
He found corpuscles in Japanese cocoons and in many specimens which had been preserved for lengthened periods in public collections.
At intervals of five days after spinning their cocoons specimens were to be opened and the chrysalides examined microscopically for corpuscles.
For special treatment towards the regeneration of an infected race, the most robust worms were to be selected, and the moths issuing from the cocoons were to be coupled in numbered cells, where the female was to be confined till she deposited her eggs.
Besides these there are many other mulberry-feeding Bombycidae in the East, principally belonging to the genera Theophila and Ocinara, the cocoons of which have not attracted cultivators.
Common cocoons enclosing chrysalides weigh each from 16 to 50 grains, or say from 300 to 600 of small breeds and from 270 to 300 of large breeds to the lb.
Under favourable conditions it is estimated that i r kilogrammes of fresh cocoons give 1 kilogramme of raw silk for commerce, and about the same quantity for waste spinning purposes.
It is only floss, injured and unreelable cocoons, the husks of reeled cocoons, and other waste from reeling, with certain wild silks, which are treated by the spun silk process, and the silk thereby produced loses much of the beauty, strength and brilliance which are characteristic of the manufactures from reeled silk.
When the cocoons have been gathered the chrysalides they contain are killed either by dry heat or by exposure to steam.
All cocoons stained by the premature death of the chrysalides (chiques), pierced cocoons, and any from other causes rendered unreelable, are put aside for the spun-silk manufacture.
Then the uninjured cocoons are by themselves sorted into classes having similar shades of colour, size and quality of fibre.
The object of reeling is to bring together the filaments (bave) from two or more (generally four or five, but sometimes up to twenty) cocoons, and to form them into one continuous, uniform, and regular strand, which constitutes the " raw silk " of commerce.
To do this, the natural gum of the cocoons which holds the filaments together must be softened, the ends of the filaments of the required number of cocoons must be caught, and means must be taken to unwind and lay these filaments together, so as to form a single uniform rounded strand of raw silk.
As the reeling proceeds the reeler has to give the most careful attention to the thickness of the strand being produced, and to introduce new cocoons in place of any from which the reelable silk has become exhausted.
In this water the cocoons are kept stirring by small brushes rotated by mechanical means, and as the silk softens the brushes gradually rise out of the water, bringing entangled with them the loose floss, and thereby revealing the main filament of each cocoon.
The cocoons are next, in sufficient number, transferred to the reeler's tray (bacinella), where the water is heated to about 140° to 150°.
According to the qualities of raw silk used and the throwing operations undergone the principal classes of thrown silk are - (1) " singles," which consist of a single strand of twisted raw silk made up of the filaments of eight to ten cocoons; (2) tram or weft thread, consisting of two or three strands of raw silk not twisted before doubling and only lightly spun (this is soft, flossy and comparatively weak); (3) organzine, the thread used for warps, made from two and rarely three twisted strands spun in the direction contrary to that in which they are separately twisted.
A portion of the eria cocoons are white, while the others are of a lively brown colour, and for the dyeing of light colours the latter require to undergo a bleaching process.
Moonga silk from Antheraea assama has generally a rather darkbrown colour, but that appears to be much influenced by the leaves on which the worm feeds, the cocoons obtained on the champaca tree (Michelia champaca) giving a fine white fibre much valued in Assam.
This increased production of medium silk, and the growing demand for fine sorts, induced many of the cocoon-growers in the Levant to sell their cocoons to Europeans, who reeled them in Italian fashion under the name of " Patent Brutia," thus producing a very fine valuable silk.
(3) Pierced cocoons-i.e.
White cocoons are exported to western Europe (394 cwt.
Turning now to instances of the opposite kind, it is known that silkworms which spin colourless cocoons are more resistant to the attacks of a certain deadly fungus than are those which spin the yellow ones.
The town is one of the most important markets for raw silk and cocoons in the south of France, and the Gardon supplies power to numerous silkmills.
There is a school of the industrial arts and handicrafts, and majolica, paper, and silk cocoons are produced.
The exports are: - Cereals, cotton, cotton seed, dried fruits, drugs, fruit, gall nuts, gum tragacanth, liquorice root, maize, nuts, olive oil, opium, rice, sesame, sponges, storax, timber, tobacco, valonia, walnut wood, wine, yellow berries, carpets, cotton yarn, cocoons, hides, leather, mohair, silk, silk stuffs, rugs, wax, wool, leeches, live stock, minerals, &c. The imports are: - Coffee, cotton cloths, cotton goods, crockery, drysalteries, fezzes, glass-ware, haberdashery, hardware, henna, ironware, jute, linen goods, manufactured goods, matches, petroleum, salt, sugar, woollen goods, yarns, &c.
The various agricultural products, cattle and mules, cheese, wines and spirits, silk cocoons and gypsum make up the bulk of the exports.
All tithes have been abolished, except those on cereals, carobs, silk cocoons, and, in the form of to% ad valorem export duties, those on cotton, linseed, aniseed and raisins (all other export duties and a fishing tax have been abolished); (4) sheep, goat, and pig tax; (5) an excise on wine, spirits and tobacco; (6) import duties; (7) stamps, court fees, royalties, licenses, &c.; (8) salt monopoly.
Cocoons and raw silk valued at 316,140 were exported in 1906-1907.