Two Spiders, the Banded and the Silky, sign their work by laying a broad white ribbon in a thick zigzag from the center to the lower edge of the web. Sometimes they put a second band of the same shape, but a little shorter, opposite the first, on the upper part of the web.
THE STICKY SNARE
The spiral part of the Garden Spider’s web is a wonderful contrivance. The thread that forms it may be seen with the naked eye to be different from that of the framework and the spokes. It glitters in the sun, and looks as though it were knotted. I cannot examine it through the microscope outdoors because the web shakes so, but by passing a sheet of glass under the web and lifting it I can take away a few pieces of thread to study. The microscope now shows me an astounding sight.
Those threads, so slender as to be almost invisible, are very closely twisted twine, something like the gold cord of officers’ sword-knots. Moreover, they are hollow. They contain a sticky moisture resembling a strong solution of gum arabic. I can see it trickling from the broken ends. This moisture must ooze through the threads, making them sticky. Indeed, they are sticky. When I lay a straw flat upon them, it adheres at once. We see now that the Garden Spider hunts, not with springs, but with sticky snares that catch everything, down to the dandelion-plume that barely brushes against the web. Nevertheless, the Spider herself is not caught in her own snare. Why?
For one thing, she spends most of her time on her resting-floor in the middle of the web, which the spiral does not enter. The resting-floor is not at all sticky, as I find when I pass a straw against it. But sometimes when a victim is caught, perhaps right at the end of the web, the Spider has to rush up quickly to bind it and overcome its attempts to free itself. She seems to be able to walk upon her network perfectly well then. Has she something on her feet which makes them slip over the glue? Has she perhaps oiled them? Oil, you know, is the best thing to prevent surfaces from sticking.
I pull out the leg of a live Spider and put it to soak for an hour in disulphide of carbon, which dissolves fat. I wash it carefully with a brush dipped in the same fluid. When the washing is finished, the leg sticks to the spiral of the web! We see now that the Spider varnishes herself with a special sweat so that she can go on any part of her web without difficulty. However, she does not wish to remain on the spiral too long, or the oil might wear away, so most of the time she stays on her safe resting-floor.
This spiral thread of the Spider’s is very quick to absorb moisture, as I find out by experiment. For this reason the Garden Spiders, when they weave their webs in the early morning, leave that part of the work unfinished, if the air turns misty. They build the general framework, they lay the spokes, they make the resting-floor, for all these parts are not affected by excess moisture; but they are very careful not to work at the sticky spiral, which, if soaked by the fog, would dissolve into sticky threads and lose its usefulness by being wet. The net that was started will be finished to-morrow, if the weather is right. But on hot days this property of the spiral is a fine thing; it does not dry up, but absorbs all the moisture in the atmosphere and remains, at the most scorching times of day, supple, elastic, and more and more sticky. What bird-catcher could compete with the Garden Spider in the art of laying snares? And all this industry and cunning for the capture of a Moth!
Then, too, what a passion the Spider has for production. I calculated that, in one sitting, each time that she remakes her web, the Angular Spider produces some twenty yards of gummy thread. The more skillful Silky Spider produces thirty. Well, during two months, the Angular Spider, my neighbor, renewed her snare nearly every evening. During that time she manufactured something like three quarters of a mile of this tubular thread, rolled into a tight twist and bulging with glue.
We cannot but wonder how she ever carries so much in her little body, how she manages to twist her silk into this tube, how she fills it with glue! And how does she first turn out plain threads, then russet foam, for her nest, then black stripes to adorn the nest? I see the results, but I cannot understand the working of her factory.