Page:The Atlantic Monthly, Volume 18.djvu/147

1866.] 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.

Now, however, a new mystery presented itself. We will admit that the spider had the power, not only to vary the size of her lines according to the number of spinners, or of the minute holes in each spinner, which were applied to the surface whence the line was to proceed, but also to make use of either golden or silver silk at will. But how was it that this yellow silk—which was quite dry and firm, though elastic, as reeled from the spider, or as spun by her in the formation of her cocoons—was nevertheless, when used for the concentric circles of the web, so viscid as to follow the point of a pin, stretching in so doing many times its length? A satisfactory explanation of this has never yet been offered, nor can be until the minute anatomy of the spinning organs is better understood, and the evolution of the silk more carefully