Insect Manufactures

CHAPTER IX.

OTHER INSECT PRODUCTIONS USEFUL TO MAN 154

INTRODUCTION.

If we are struck with wonder and admiration at the progress of the arts and manufactures, and have daily reason to congratulate ourselves on the skill and ingenuity of our fellow-creatures, by which our comforts and conveniences are so much increased; it must also occasionally have crossed our minds, that some of the meaner creatures, though not gifted with our reasoning powers, and therefore not able to profit by the experience of the past, are yet employed in their several departments, and according to their several wants, in exceedingly curious and useful manufactures, mostly designed for the shelter and preservation of themselves or their offspring, but serving, not unfrequently, a higher purpose, in administering to the wants of mankind.

In reading the history, or in watching the proceedings of birds and insects, how many remarkable instances do we meet with of that which may be called manufacture, though performed without hands! How curious to watch in the early spring the proceedings of those busy basket-making birds, the rooks! Rude and clumsy as their nests may at first appear, it is just the sort of workmanship best calculated for their wants. They do not, indeed, choose the smooth and flexible osier-twigs which we should think necessary for basket-making, but they contrive by means of brittle, dead, forked sticks, to plait together a strong bristling out-work, within which they interweave a finer basket-work of fibrous roots, rude indeed, but not inelegant or unsuitable. Then, among birds and insects too, what persevering and industrious carpenters, masons, tailors, miners, and weavers may we not find. Perhaps there are not many persons who have watched the mason-wasps boring their galleries in brick or sand, or building the round towers which serve them as out-works; nor the mason-bee, as she plasters together her neat mud-wall cottage or cell, as the future habitation of her young; but there are few persons unacquainted with the masonry of the chimney swallow, or of the house-martin twittering on the eaves. With no other tools than those which nature supplies, how cleverly do these creatures shape and mould their nests into the required form, using for their work a mortar carefully prepared by their own labour and skill, and just of the consistency required. Few, again, may have had an opportunity of seeing carpenter-bees boring holes in posts or palings, and forming their smoothly chiselled cells, or of inspecting the partitioned galleries dug out in old timber by carpenter-wasps; but perhaps many persons have observed the colonies of emmets, or carpenter-ants, working in the trunks of decaying oak or willow trees; or they may have listened to that interesting carpenter-bird, the wood-pecker, tapping and boring into trees, in pursuit of insects, and for the purpose of making a nesting-place for its young. Most of us know only by hearsay that there are tailor-birds, common enough in American orchards, who sew together broad pieces of grass to make their nests, working them through and through, as if actually done with a needle; but almost every one can say from his own knowledge, that there are weaver-birds, such as our common hedge-sparrow and chaffinch, who weave a circular piece of haircloth for the interior of their nests, each hair being collected and interwoven singly, and always bent so as to lie smoothly in the hollow of the nest. Then who shall describe all the wondrous proceedings of tent-making caterpillars, upholsterer-bees, turret-building ants, net-making spiders, paper and card-making wasps, and spinning worms? Volumes have been written, and volumes might still be written on the history of these creatures. Any one possessing a garden, and taking delight therein, has ample opportunity of watching the habits of birds and insects, and of confirming, if not of adding to, the accounts given by naturalists, of the commoner species. But we must still be indebted to the patient observations of those who have made insects or birds their especial study, for many of the most curious particulars, and for all our knowledge of rare or foreign species.

Interesting as is the whole subject of bird and insect manufactures, there is one department in which we are more concerned than the rest; namely, that in which the product can be applied to our own use, either in the way of food or clothing. Now this department is supplied wholly by insects, no bird, that we are aware of, producing by its own manufacturing powers, any substance that can be so employed, unless, indeed, we except the curious edible nests of the Java swallow, which have been converted by the taste of oriental epicures into an article of food.

Let us then proceed to notice such of the insect manufactures as are useful to man, and trace, at the same time, the history and performances of these small but not insignificant manufacturers.

CHAPTER I.. Manufacture of Silk by Caterpillars of Various Kinds.

MANUFACTURE OF SILK BY CATERPILLARS OF VARIOUS KINDS.

The most important of all the insect manufactures is doubtless that of silk-spinning. It seems almost past belief that the magnificent velvets, satins, and silks which form so elegant a part of female attire, and which are heaped together in such costly profusion in the shops of the metropolis, and in those of all considerable towns, whether in our own, or in foreign countries—that these splendid fabrics, together with all ribbons, gauzes, damasks, or other articles composed of silk, should owe the raw material of which they are formed to the labours of a race of little creeping caterpillars, which in this their early and imperfect state spin for themselves cocoons, or cases of silk, where they may quietly undergo their changes until they become perfect winged insects.

CATERPILLAR SUSPENDED BY ITS SILKEN THREAD. ]

The astonishing task of supplying silk for the whole civilized world is performed almost without exception by the common silkworm, or caterpillar of the mulberry-tree moth. But it must not be supposed that this is the only silk-producing insect. On the contrary, all the caterpillars of butterflies and moths have the power of spinning a certain quantity of silken thread, however small, and however inferior to that of the silkworm, properly so called. It is very common in gardens to see numbers of caterpillars dangling by their silken threads from the young branches of fruit-trees. In this way they let themselves down, or break their fall if blown off by the wind, or otherwise shaken from their favourite tree. And in the case of some caterpillars when the insect has completed the term of its existence and becomes a chrysalis, it suspends itself by silken cords to some fixed point, where it remains in complete repose, without food, perhaps for months before the perfect winged insect bursts forth, as different a creature from the caterpillar as the chrysalis is from either,—and yet these are but three different states of existence of the same insect.

CHRYSALIS SUSPENDED BY SILKEN CORDS. ]

According to the particular species of caterpillar, the silk will vary in strength and fineness, and also in colour, but seldom will it be found strong enough, or in sufficient quantity to be of use to us. The insects themselves employ it in many ways for their own safety and shelter. How common it is to find some of the leaves of a lilac-tree made up into little rolls, or folded together at their edges, where they stick so fast that it requires some little force to pull them asunder. This is the work of a small caterpillar, whose subsistence is found on that tree. A single egg has been laid on each leaf selected by the parent moth, and soon after it is hatched, the caterpillar begins rolling up the lilac leaf, and fastening the edges with silk. This is a work of time, but gradually proceeds as the caterpillar increases in strength, until at last it is shut up in a gallery of its own making, safe from the attacks of birds and larger insects. The leaves of various other trees are rolled in a somewhat similar manner, as those of the oak, the willow, and the rose, and also those of humbler plants, as the plantain, nettle, thistle, &c. The mode in which these leaf-rolling caterpillars set to work to form convenient habitations of the leaves of the plants on which they feed, is well described by Kirby and Spence.

OAK LEAF ROLLED BY A CATERPILLAR. ]

“Some of these merely connect together with a few silken threads several leaves, so as to form an irregular packet, in the centre of which the little hermit lives. Others confine themselves to a single leaf, of which they simply fold one part over the other. A third description form and inhabit a sort of roll, by some species made cylindrical, by others conical, resembling the papers in which grocers put their sugar, and as accurately constructed; only there is an opening left at the smaller extremity for the egress of the insect in case of need. If you were to see one of these rolls, you would immediately ask by what mechanism it could possibly be made—how an insect, without fingers, could contrive to bend a leaf into a roll, and to keep it in that form until fastened with the silk which holds it together? The following is the operation: the little caterpillar first fixes a series of silken cables from one side of the leaf to the other: she next pulls at these cables with her feet; and when she has forced the sides to approach, she fastens them together with stronger threads of silk. If the insect finds that one of the larger nerves of the leaf is so strong as to resist her efforts, she weakens it by gnawing it here and there half through. What engineer could act more sagaciously? To form one of the conical or horn-shaped rolls, which are not composed of a whole leaf, but of a long triangular portion cut out of the edge, some other manœuvres are requisite. Placing herself upon the leaf, the caterpillar cuts out with her jaws the piece which is to compose her roll. She does not, however, entirely detach it; it would then want a base. She detaches that part only which is to form the contour of the horn. This portion is a triangular strap, which she rolls as she cuts. When the body of the horn is finished, as it is intended to be fixed upon the leaf in nearly an upright position, it is necessary to elevate it. To effect this, she proceeds as we should with an inclined obelisk. She attaches threads, or little cables, towards the point of the pyramid, and raises it by the weight of her body.”

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