3. A great disadvantage of the spider’s silk is, that it cannot be wound off the ball like that of the silk-worm, but must necessarily be carded. By this latter process, its evenness, which contributes so materially to its lustre, is destroyed.
The ferociousness and pugnacity of the spiders are not exaggerated; they fight like furies. Their voracity, too, is almost incredible, and it is very questionable whether the mere collection of flies sufficient to feed a large number of the spiders would not involve an amount of expense fatal to the project as a lucrative undertaking. The strength of the spiders’ filament is, if anything, overstated by Réaumur. Deficiency of lustre arising from the carding of the filaments is common to the spider-fabric and to spun silk; this objection would, perhaps, not be of very great weight but for the decisive calculation by which Réaumur showed the comparative amount of production between the spider and the silk-worm.
The largest cocoons weigh four, and the smaller three grains each; spider-bags do not weigh above one grain each; and, after being cleared of their dust, have lost two-thirds of this weight; therefore the work of twelve spiders equals that of only one silk-worm; and a pound of spider-silk would require for its production 27,648 insects. But as the bags are wholly the work of the females, who spin them as a deposit for their eggs, it follows that 55,296 spiders must be reared to yield one pound of silk: yet this will be obtained only from the best spiders; those large ones ordinarily seen in gardens, &c., yielding not more than a twelfth part of the silk of the others. The work of 280 of these would therefore not yield more silk than the produce of one industrious silk-worm, and 663,552 of them would furnish only one pound of silk!
Although Réaumur’s report completely extinguished Mr. Bon’s project in France, it was revived in England two or three times in the early part of the last century. Swift has not neglected to make it a portion of his unrivalled satire against speculators and projectors, in his account of Gulliver’s visit to the Academy of Lagado:
“I went into another room, says he, where the walls and ceilings were all hung round with cobwebs, except a narrow passage for the artist to go in and out. At my entrance he called out to me not to disturb his webs. He lamented the fatal mistake the world had been so long in, of using silk-worms, while we had such plenty of domestic insects, who infinitely excelled the former, because they understood how to weave as well as spin. And he proposed further, that, by employing spiders, the charge of dyeing silk should be wholly saved; whereof I was fully convinced, when he showed me a vast number of flies most beautifully colored, wherewith he fed his spiders, assuring us that the webs would take a tincture from them, and as he had them of all hues, he hoped to suit every body’s fancy, as soon as he could find proper food for the flies, of certain gums, oils, and other glutinous matter to give a strength and consistency to the threads.”
The Ingenuity of Spiders.—Mr. Thomas Ewbank of New York, in a letter to the Editor of the Journal of the Franklin Institute, bearing date September 20th, 1842, gives us the following interesting description of the ingenuity of the Spider.
“The resources of the lower animals have often excited admiration, and though no comprehensive and systematic series of observations have yet been made upon them(?), the time is, I believe, not distant when the task will be undertaken—perhaps within the next century. But whenever and by whomsoever accomplished, the mechanism of animals will then form the subject of one of the most interesting and useful volumes in the archives of man.
“Among insects, spiders have repeatedly been observed to modify and change their contrivances for ensnaring their prey. Those that live in fields and gardens often fabricate their nets or webs vertically. This sometimes occurs in locations where there is no object sufficiently near to which the lower edge or extremity of the web can properly be braced; and unless this be done, light puffs or breezes of wind are apt to blow it into an entangled mass. Instead of being spread out, like the sail of a ship, to the wind, it would become clewed over the upper line, or edge, like a sail when furled up. Now how would a human engineer act under similar circumstances? But ere the reader begins to reflect(!), he should bear in mind that it would not do to brace the web by running rigging from it to some fixed or immovable object below—by no means;—for were this done, it could not yield to impulses of wind; the rigging would be snapped by the first blast, and the whole structure probably destroyed.
“Whatever contrivances human sagacity might suggest, they could hardly excel those which these despised engineers sometimes adopt. Having formed a web, under circumstances similar to those to which we have referred, a spider has been known to descend from it to the ground by means of a thread spun for the purpose, and after selecting a minute pebble, or piece of stone, has coiled the end of the thread round it. Having done this, the ingenious artist ascended, and fixing himself on the lower part of the web, hoisted up the pebble until it swung several inches clear of the ground. The cord to which the weight was suspended was then secured by additional ones, running from it to different parts of the web, which thus acquired the requisite tension, and was allowed, at the same time, to yield to sudden puffs of wind without danger of being rent asunder.
“A similar instance came under my notice a few days ago. A large spider had constructed his web, in nearly a vertical position, about six feet from the ground, in a corner of my yard. The upper edge was formed by a strong thread, secured at one end to a vine leaf, and the other to a clothes line. One part of the lower edge was attached to a Penyan sun-flower, and another to a trellis fence, four or five feet distant. Between these there was no object nearer than the ground, to which an additional brace line could be carried; but two threads, a foot asunder, descended from this part of the web, and, eight or ten inches below it, were united at a point. From this point, a single line, four or five inches long, was suspended, and to its lower extremity was the weight, a living one, viz. a worm, three inches long, and one-eighth of an inch thick. The cord was fastened around the middle of the victim’s body, and as no object was within reach, all its writhings and efforts to escape were fruitless. Its weight answered the same purpose as a piece of inanimate matter, while its sufferings seemed not in the least to disturb the unconcerned murderer, who lay waiting for his prey above.