The male is winged, and the female not. The latter is of an oval form, convex on the back, and covered with a white downy substance resembling the finest cotton. The antennæ are half as long as the body, and the legs are short and black.
Cochineal is one of the most valuable substances that are used in dyeing. As imported into this country, it is in the form of a reddish shrivelled grain, covered with a white bloom or powder.
The cochineal insects adhere in great numbers, and in an apparently torpid state, to the leaves of the prickly pear. At a certain period of the year they are carefully picked or brushed off, either by a bamboo twig shaped somewhat into the form of a pen, or by an instrument formed of a squirrel's or stag's tail: and so tedious is the operation, that the persons employed in it are sometimes obliged to sit for hours together beside a single plant. In some parts of South America the insects, after being collected in a wooden bowl, are thickly spread upon a flat dish of earthen ware, and cruelly placed alive over a charcoal fire, where they are slowly roasted, till their downy covering disappears, and they are perfectly dried. In other parts they are killed by being thrown into boiling water, by being placed in ovens, or being exposed in heaps to the sun.
The quantity of cochineal annually exported from South America is said to be worth more than 500,000l. sterling, a vast sum to arise from so minute an insect; and the present annual consumption of cochineal in England has been estimated at about 150,000 pounds' weight.
It is for dyeing scarlet that cochineal is chiefly in demand; but although a peculiarly brilliant dye is now obtained from it, this substance gave only a dull crimson colour until a chemist of the name of Kuster, who, about the middle of the seventeenth century, lived at Bow, near London, discovered the art of preparing it with a solution of tin. Cochineal, if kept in a dry place, may be preserved, without injury, for a great length of time. An instance has been mentioned of some of this dye, 130 years old, having been found to produce the same effect as though it had been perfectly fresh.
The attention of the East India Company has, for many years, been directed to the production of cochineal in the East, but hitherto with little success. That which has been brought from India is very small, and greatly inferior to what is imported from New Spain.
An imitation of cochineal is made by a preparation of bullock's blood, and some other ingredients.
261. The SILK-WORM is a smooth and somewhat lead-coloured caterpillar, produced from the eggs of a moth (Phalæna mori) which is found in great abundance in China, the East Indies, the Levant, several parts of Italy, and the South of Spain.
So great is the importance of silk, in a commercial view, that, in most of the Eastern countries of the world, a close attention is paid to the growth and cultivation of the insects by which it is produced. Each moth lays about two hundred small straw-coloured eggs. As soon as the worms are hatched they are fed with the tenderest leaves of the mulberry-tree, or with these leaves chopped very fine; and, when they have attained sufficient strength, they are removed into wicker baskets, or placed upon shelves made of wickerwork. Here they feed for about thirty days, until they are full grown, when they are furnished with little bushes of heath or broom. On these they spin the nests in which they are about to change into chrysalids. These nests have the general name of coccoons, and consist of somewhat oval-shaped balls of silk, of marigold colour. The exterior of the coccoon is composed of a rough cotton-like substance, called floss. Within this is the thread, which is more distinct and even; and appears arranged in a very irregular manner, winding off first from one side of the coccoon, and then from the other. Previously to the silk being wound from the coccoons they are baked for about an hour to kill the chrysalids they contain. When the silk is to be wound off, the coccoons are put into small coppers or basins, of water, each placed over a small fire. The ends of the threads are found by brushing the coccoons gently with a whisk made for the purpose; and so fine are these threads that eight or ten of them are generally rolled off into one. In winding them, they are each passed through a hole in an horizontal iron bar placed at the edge of the basin, which prevents them from being entangled.
The art of manufacturing silk was known to the ancients; but in Europe this commodity, long after its invention, was of very great value. We are informed that, in the third century, the wife of the Roman Emperor Aurelian entreated him to give her a robe of purple silk, and that he refused this under an allegation that he could not buy such a robe for its weight in gold.