"—set to work millions of spinning worms,
That in their green shops weave the smooth-hair'd silk
To deck her sons[643],"
she was conferring upon them a benefit scarcely inferior to that consequent upon the gift of wool to the fleecy race, or a fibrous rind to the flax or hemp plants; and that mankind is not under much less obligation to Pamphila, who, according to Aristotle, was the discoverer of the art of unwinding and weaving silk, than to the inventors of the spinning of those products[644].
It seems to have been in Asia that silk was first manufactured; and it was from thence that the ancients obtained it, calling it, from the name of the country whence it was supposed to be brought, Sericum. Of its origin they were in a great measure ignorant, some supposing it to be the entrails of a spider-like insect with eight legs, which was fed for four years upon a kind of paste, and then with the leaves of the green willow, until it burst with fat[645]; others, that it was the produce of a worm which built clay nests and collected wax[646]; Aristotle, with more truth, that it was unwound from the pupa of a large horned caterpillar[647]. Nor was the mode of producing and manufacturing this precious material known to Europe until long after the Christian æra, being first learnt about the year 550 by two monks, who procured in India the eggs of the silk-worm moth, with which, concealing them in hollow canes, they hastened to Constantinople, where they speedily multiplied, and were subsequently introduced into Italy, of which country silk was long a peculiar and staple commodity. It was not cultivated in France until the time of Henry the Fourth, who, considering that mulberries grew in his kingdom as well as in Italy, resolved, in opposition to the opinion of Sully, to attempt introducing it, and fully succeeded.
The whole of the silk produced in Europe, and the greater proportion of that manufactured in China, is obtained from the common silk-worm; but in India considerable quantities are procured from the cocoons of the larvæ of other moths. Of these the most important species known are the Tusseh and Arindy silk-worms, of which an interesting history is given by Dr. Roxburgh in the Linnean Transactions[648]. These insects are both natives of Bengal. The first (Attacus Paphia,) feeds upon the leaves of the Jugube tree (Rhamnus Jujuba) or Byer of the Hindoos, and of the Terminalia alata glabra, Roxburgh, the Asseen of the Hindoos, and is found in such abundance as from time immemorial to have afforded a constant supply of a very durable, coarse, dark-coloured silk, which is woven into a cloth called Tusseh-doot'hies, much worn by the Brahmins and other sects; and would doubtless be highly useful to the inhabitants of many parts of America and of the South of Europe, where a light and cool, and at the same time cheap and durable dress, such as this silk furnishes, is much wanted. The durability of this silk is indeed astonishing. After constant use for nine or ten years it does not show any signs of decay. These insects are thought by the natives of so much consequence, that they guard them by day to preserve them from crows and other birds, and by night from the bats.—The Arindy silk-worm (Attacus? Cynthia, Drury), which feeds solely on the leaves of the Palma Christi, produces remarkably soft cocoons, the silk of which is so delicate and flossy, that it is impracticable to wind it off: it is therefore spun like cotton; and the thread thus manufactured is woven into a coarse kind of white cloth of a loose texture, but of still more incredible durability than the last, the life of one person being seldom sufficient to wear out a garment made of it. It is used not only for clothing, but for packing fine cloths, &c. Some manufacturers in England to whom the silk was shown, seemed to think that it could be made here into shawls equal to any received from India.
Other species, as may be inferred from an extract of a letter given in Young's Annals of Agriculture[649], are known in China, and have been recently introduced into India. "We have obtained," says the writer, "a monthly silk-worm from China, which I have reared with my own hands, and in twenty-five days have had the cocoons in my basins, and by the twenty-ninth or thirty-first day a new progeny feeding in my trays. This makes it a mine to whoever would undertake the cultivation of it."
Whether it will ever be expedient to attempt the breeding of the larvæ of any European moths, as Catocala pacta, Sponsa, &c. proposed with this view by Fabricius[650], seems doubtful, though certainly many of them afford a very strong silk, and might be readily propagated; and I have now in my possession some thread more like cotton than silk spun by the larva of a moth, which when I was a very young entomologist I observed (if my memory does not deceive me) upon the Euonymus, and from the twigs of which (not the cocoon) I unwound it. It is even asserted that in Germany a manufacture of silk from the cocoons of the emperor moth (Saturnia Pyri?) has been established[651]. There seems no question, however, that silk might be advantageously derived from many native silk-worms in America. An account is given in the Philosophical Transactions of one found there, whose cocoon is not only heavier and more productive of silk than that of the common kind, but is so much stronger that twenty threads will carry an ounce more[652]. Don Luis Neé observed on Psidium pomiferum and pyriferum ovate nests of caterpillars eight inches long, of gray silk, which the inhabitants of Chilpancingo, Tixtala, &c. in America, manufacture into stockings and handkerchiefs[653]. Great numbers of similar nests of a dense tissue, resembling Chinese paper, of a brilliant whiteness, and formed of distinct and separable layers, the interior being the thinnest and extraordinarily transparent, were observed by Humboldt in the provinces of Mechoacan and the mountains of Santarosa at a height of 10,500 feet above the level of the sea, upon the Arbutus Madrôno and other trees. The silk of these nests, which are the work of the social caterpillars of a Bombyx (B. Madrôno), was an object of commerce even in the time of Montezuma, and the ancient Mexicans pasted together the interior layers, which may be written upon without preparation, to form a white glossy pasteboard. Handkerchiefs are still manufactured of it in the Intendency of Oaxaca[654]. De Azara states that in Paraguay a spider, which is found to near the thirtieth degree of latitude, forms a spherical cocoon (for its eggs) an inch in diameter, of a yellow silk, which the inhabitants spin on account of the permanency of the colour[655]. And according to M. B. de Lozieres, large quantities of a very beautiful silk, of dazzling whiteness, may be collected from the cocoons even of the Ichneumons that destroy the larvæ of some moth in the West Indies which feed upon the indigo and cassada[656].
It is probable, too, that other articles besides silk might be obtained from the larvæ which usually produce it, particularly cements and varnishes of different kinds, some hard, others elastic, from their gum and silk reservoirs, from which it is said the Chinese procure a fine varnish, and fabricate what is called by anglers Indian grass[657]. The diminutive size of the animal will be thought no objection, when we recollect that the very small quantity of purple dye afforded by the Purpura of the ancients did not prevent them from collecting it.
I now conclude this long series of letters on the injuries caused by insects to man, and the benefits which he derives from them; and I think you will readily admit that I have sufficiently made good my position, that the study of agents which perform such important functions in the economy of nature must be worthy of attention. Our subsequent correspondence will be devoted to the most interesting traits in their history,—as their affection to their young, their food and modes of procuring it, habitations, societies, &c.
I am, &c.