1356

ARBORETUM AND FRUTICETUM.

PART III.

to Count Dandolo, a hundred trees, great and small, will furnish 7,000 lb. ofleaves, and these will be sufficient for 200,000 silkworms.

Management of the SWcworm. The silkworm is the popular name for the larva, or caterpillar, ofthe moth known to entomologists as the iJombyx m6ri Fab .; a native of China, which was introducedinto Europe, as we have before seen, in 550. Fig. 1224. represents this insect, in its various stages ,

1224 ;

LCJS

a

of the natural size: a, the eggs, which, when good, are of a pale slate or dark lilac colour; bis the larva, or caterpillar, when full grown ; c is the insect in its chrysalis state, after the silk hasbeen removed ; d is the male imago, or perfect insect; and e, the female. When full grown, thelarva is nearly 3 in. long, of a yellowish grey colour, with a horn-like process on the last joint of thebody. The eggs, in Britain, may be purchased in Covent Garden Market, at 10s. per oz.; and careshould be taken that .they are of the proper colour; because those that are of a pale yellowcolour are imperfect. They are preserved in a cool place, that is, in a temperature of from 10° to 12°Reaumur (55° to 59° Fahr.), till wanted for use, and will retain their vitality upwards of a year.To hatch them, a temperature of 86° Fahr. is required ; for which purpose, in most parts ofEurope where the silkworm is cultivated, the rooms used for that purpose are heated by stoves;though in the East Ind’es, in the Islands of France and Bourbon, &c., and in the southernparts of the United States, the natural temperature of the air is found sufficient. The houses inwhich the insects are kept are built with numerous windows, for the admission of air; and fur-nished with tables or shelves, on which the insects r a.re kept. These shelves have movable ledges,of 1 in. or more in height, on each side, to confine the insects ; and several stages of them may beformed one above the other, if care be taken that they are not attached to the wall, in order to admita free circulation of air on every side. When the mulberry begins to unfold its leaves, it is time tocommence the hatching of the eggs. These should be placed on the shelves in the temperaturementioned; and when they begin to turn white, which will be in about ten days, they should becovered with sheets of writing paper, turned up at the edges, and pierced full of holes with a largeknitting needle. On the upper side of the paper should be laid some young twigs of mulberry,which the insects will smeli; and, crawling through the holes in the paper, will begin to eat as soonas they are hatched. As fastas these twigs become covered with insects, they are carefully takenup and removed to another shelf, where they are placed on whity-brown or any- absorbent paper,about one to every square inch. The silkworm changes its skin four times before it spins its cocoon.Its life is thus divided into five ages; during the first of which it is fed with chopped or youngleaves, fresh ones being given as soon as it has eaten what it had before. At this time it frequentlyappears to sleep, when it should on no account be disturbed. When the silkworm is in its secondage, it may be fed with young leaves entire, or old ones chopped small; a great part of this age alsois passed in sleep. During the third age the silkworms become more lively and vigorous, and they willdevour full-grown leaves without cutting. In the fourth age the silkworm changes to a flesh colour,and eats greedily. In the fifth age the silkworm will eat the coarsest leaves, and it should be fedabundantly night and day, and have plenty of air and warmth. Each change is preceded by a day ortwo’s apparent sickness and want of appetite in the insect, which becomes torpid before the changeof its skin takes place. During the whole period of the silkworm’s life, the litter made by the wasteleaves, &c., must be frequently removed, theinsectsbeing attracted to one corner of their shelves withsome fresh leaves, while the other parts are cleaned. When the caterpillars cease to eat, and run to andfro, frequently looking up, it is an indication that they are preparing to make their cocoons. Theywill now have become transparent, of a clear pearly colour, and the green circles round their bodieswill have assumed a golden hue, Twigs of oak, tufts of dandelion, rolled up shavings from thecabinet-maker, cornets of paper, or sprigs of alaternus, phillyrea, heath, or broom, as may be mostconvenient, are then placed on the tables or shelves, to serve as a support for the insects ; the tablesor shelves having been previously cleared of all litter, and the branches, or other materials, havingbeen so arranged as to give the insects a feeling of security. They then immediately begin to maketheir cocoons, which are exuded in threads from the mouth, and which are generally completed infrom four to seven days. When the insects have done working, the cocoons are taken from thetwigs, and sorted : those that are double, or in any way imperfect, are thrown aside ; a certain num-ber are selected to breed from, and the rest are set apart for reeling the silk. The first operationwith these last is to kill the insects enclosed. This is performed, in Italy, by exposing the cocoons tothe heat of the sun for three days, from 10 o’clock a. m. to 5 o’ clock p. m., when the thermometerstands at 88° Fahr. In France they are put into bags or baskets, and enclosed for half an hour inovens heated to 88°; but in America they are generally placed in sieves or boxes, having perforatedbottoms; these are covered very closely with a woollen cloth, and then placed over the steameither of boiling water, or boiling whiskey or rum. (See New York Farm., vol. vi. p. 227.) The in-sects being killed, and the cocoons cleared of the external floss .which is manufactured under thename of floss, or spun, silk), they are thrown by handfuls into basins of pure soft water, placed oversmall furnaces of charcoal fires. W T hen the water is almost at the boiling point, the cocoons are sunkwith a whisk of broom or peeled birch under water for two or three minutes, to soften the gum andloosen the fibre. This, however, is unnecessary when they have been killed by the steam of boiling