Page:The New International Encyclopædia 1st ed. v. 18.djvu/212

* SILKWOKM. 170 SILKWORM. France now supplies her own market and ex- ports 300,000 ounces of silkworm eggs annually. In worms affected with flacherie the food fer- ments in the alimentary tract and sustains vi- brios and certain fungi. This disease is proba- bly induced by improper care of the eggs. Gat- tine is probably only a modification of flacherie. The cause of grasserie (q.v.) is unknown. It is the least fatal of silkworm diseases. To keep silkworms healthy they must be reared in a suitable and constant temperature. Humidity, ventilation, and cleanliness must also be strictly and constantly attended to. Lime is used for whitewashing 'the walls and buildings in which the worms are reared, and sulphur fumes for sterilizing the trays. CuLTunE OF 81LKWOKMS. The leaf of the white mulberry (Mori(s aiha) is apparently the nat- ural food of the domestic silkworm. There are many horticultural varieties of this plant, some much better adapted than others to commercial silk culture, and some better suited to certain localities. The Mortis moretti, the Morus multi- caulis, and the black nuilberry (Morus nigra) are also used. The red mulberry (Morus rubra) does not make good food, and the paper mulberry (Broussonetia papyrifera) is also valueless. The best varieties of mulberries are propagated by means of seeds and by cuttings. The trees should be planted well apart and should be pruned so as to form a short trunk and a close low head. Silkworm eggs are kept through the winter at a low temperature, the embryo beginning to take form when the temperature rises above 50° F. The re- ceptacle in which they are stored should be - ventilated, the air should not be moist, and great care should be taken to keep them out of the reach of mice and insects. The eggs are hatched in an artificial incubator or by natural heat. When an incubator is used the tempera- ture should be gradually increased until 73° F. is reached. The whitening of the eggs de- notes the near approach of the hatching. The eggs should then be covered with sheets of tulle or finely perforated paper, sprinkled over with finely cut white mulberry leaves. The young caterpillars will at once mount to the leaves, and should be fed eight to ten times during twenty-four hours. After each feeding the lower sheet of perforated paper or tulle should be re- moved with the frass. About the sixth day they will begin to molt and pass into the second stage. As the worms increase in size, paper in which the perforations are larger should be used, and the same general directions followed for each stage until the fifth has been reached. The worms have now grown to nearly full size, and are very voracious, and it is very difficult to satisfy their appetite. After five days in the fifth stage they are ready to spin. In making preparations for spinning, dry brush, bundles of straw or shavings or finely split-up wood may be used. The brush or straw should be placed up- right between the feeding shelves, in rows, about 16 inches apart, the tops spread out to form arches and to allow the worms plenty of room to spin. The temperature during spinning should be 75° F., and the humidity through- out the rearing about 65°. The rearing-room should be well ventilated, and before introduc- ing the worms should be disinfected with chloride of lime or sulphur. One ounce of eggs con- tains approximately 40.000, and the space re- quired may be estimated by allowing one square yard for tliis amount at birth, on the fourth day two square yards, for the second stage four square yards, tliree days later eight square yards, for the third stage 16 square yards, for the fourth stage 32 square yards, and for the fifth stage 00 square j-ards. Plenty of space is desirable, since when crowded the worms will not be so robust. A mean temperature of about 74° F. is the best. There are many commer- cial varieties of the silkworm graded ac- cording to the size, color, and quality of the co- coon. When the cocoons are completed, which is known by the absence of any soimd within, they are carefully sorted, and a certain number are kept for laying. The sexes are readily known by the difference of shape as well as of size, the female being plumper and the male, besides being much smaller, having a central de- pression and sharper extremities. The French growers sort them into nine varieties, those which are less compact, or in which the worm has died — a fact kno«Ti by external indications — being separated from the good ones. When the sorting is finished, the cocoons are placed in an oven with a gentle heat, which kills the inclosed chrysalis, otherwise they would all be- come perforated by the insect eating through. The cocoons are then ready for the first stage in the manufacturing process, which consists in the removal and winding of the fibrous cover- ing as described under SiLK. Other Silkworms. It is supposed by some entomologists that the original wild silkworm from wiiich descended the silkworm of commerce is a species known as Theophila Huttoni, which occurs in .Japan, the Northwest Himalayas, and Assam. Tlie moth is of the same size as that of Bombyx niori, is light brown in color, and has the characteristic markings on the wings. The larva almost precisely resembles the domestic silkworm, but has a pair of small black thorns on the back of each segment of the abdomen. It seems very unlikely, however, that this species '■ could have been the ancestor of Bombyx mori, since it lacks palpi, which are present in the Bomby.x. Oriental people have utilized the cocoons of a number of species of bombycid moths in the manufacture of silk goods. The so-called tussah, tusseh, or tusser silkworm is Antherwa mylitta, a species which occurs in China, India, an(l Ceylon. In Upper India this silk is extensively produced, and the cocoons are collected id the jungle districts by the Sahars and other half- wild castes w-ho live in such places. Other silk- worms which are said to be used in the manu- facture of tusseh silk are Antherwa pernyi, from Cliina; Antherwa Assama (Satitrnia Perotictti and Antherwa mezanhoorm are synonyms of this species), a native of Assam, and there called 'moonga' or 'moogha ;' Antherwa Roylei, from India; Antherwa Helferi from Sikhim; Antherwa jana. from Java ; Antherwa Frithii. from Sikhim, Bhutan, and Darjeeling; and Antherwa larissa, from Java. The very large and beautiful Attacus atlas, from India, Ceylon. Burma, and Java, is also said to produce cocoons used in making tusseh silk. The wild silkworms which have received the