The Atlantic Monthly | Page 9

be unwound, and so made of any further use.
I tried now to ascertain how much silk could be obtained from a single
spider at once. It will be remembered that the first specimen, wound on
Folly Island, was one hundred and fifty yards in length, and weighed
one third of a grain. I now exhausted the supply of a spider for three
days, using the same spindle, one inch in diameter, and turning this at
the rate of one hundred and sixty times per minute. On the first day I
reeled for twenty minutes, which gave two hundred and sixty-six and
two thirds yards; on the third day, the second being Sunday, for
twenty-five minutes, giving three hundred and thirty-three and one
third yards; and on the fourth day, for eighteen minutes, giving two
hundred and thirty-three and one third yards,--amounting in all to eight
hundred and thirty-three and one third yards in three or four days. This
was all that could be got, and the spider herself seemed unable to
evolve any more; but on killing her and opening her abdomen, plenty
of the gum was found in the little silk bags into which it is secreted. As
this has always been the case, I have concluded that the evolution of the
silk is almost entirely a mechanical process, which is but little
controlled by the spinners themselves, and that the gum requires some
degree of preparation after it is secreted before it is fit for use as silk;
for it must be remembered that with the spider, as with the silk-worm,

the silk is formed and contained in little bags or glands in the abdomen,
not as threads, but as a very viscid gum. This passes in little tubes or
ducts to the spinners, through minute openings, in which it is drawn out
into filaments, uniting and drying instantly in the air, and so forming
the single fibre from each spinner.
The silk obtained the first day was of a deep yellow; to my great
astonishment, the second reeling from the same spider gave silk of a
brilliant silver-white color; while on the third occasion, as if by magic,
the color had changed again, and I got only yellow silk. The hypothesis
of individual peculiarity, adopted the previous year to explain why
some spiders gave yellow, and others white silk, was now untenable;
and, remembering that, beside these two positive colors there was also
(and indeed more commonly) a light yellow, as if a combination of the
other two, I saw that the real solution of the mystery must lie in the
spinners themselves. Examining carefully the thread as it came from
the body, it was seen to be composed of two distinct portions, differing
materially in their size, their color, their elasticity, and their relative
position; for one of them was white and inelastic, crinkling and flying
up when relaxed, and seemed to proceed from the posterior of the two
principal pairs of spinners, while the other was larger, yellow, so
elastic that when relaxed it kept its direction, and seemed to come from
the anterior pair of spinners, and so, in the inverted position of the
spider, was above the other. By putting a spider under the influence of
chloroform, and then carrying the first thread under a pin stuck in a
cork to one part of a spindle, and the second or yellow line over another
pin to a different part of the spindle, I reeled off from the same spider,
at the same time, two distinct bands of silk, of which one was a deep
golden-yellow, the other a bright silver-white; while, if both threads ran
together, there was formed a band of light yellow from the union of the
two. Thinking such a difference must subserve some use in the
economy of the insect, I made a more careful examination of its webs.
At first sight these resembled those of most geometrical spiders, in
being broad, rounded, nearly vertical nets; but they were unusually
large, and in their native woods often stretched between trees and
across the paths, so as to be two, three, and even more, feet in diameter,
and in my room at Mt. Pleasant hung like curtains before the windows.

They were of a bright yellow color and very viscid; but now I noticed
that neither the color nor the viscidity pertained to the entire net, for
although the concentric circles constituting the principal part of the web
were yellow, and very elastic, and studded with little beads of gum,
(Fig 3,) yet the diverging lines or radii of the wheel-shaped structure,
with all the guys and stays by which it was suspended and braced, were
dry and inelastic, and of a white or lighter yellow color.
[Illustration: Fig. 3. Silk