Back Aa

Insect Adventures

Close

<h2 id="chapter-21"><ANTIMG src="images/i_242.jpg" alt="" /> CHAPTER XXI THE SPIDER’S TELEGRAPH-WIRE</h2> Of the six Garden Spiders I have noticed, two only, the Banded and the Silky Spiders, stay constantly in their webs, even under the blinding rays of a fierce sun. The others, as a rule, do not show themselves until nightfall. At some distance from the net they have a rough and ready retreat in the brambles, a hiding-place made of a few leaves held together by stretched threads. It is here that they usually remain in the daytime, motionless and sunk in meditation. But the shrill light that vexes them is the joy of the fields. At such time, the Locust hops more nimbly than ever, more gayly skims the Dragon-fly. Besides, the sticky web, in spite of the rents suffered during the night, is still in fairly good condition. If some giddy-pated insect allow himself to be caught, will the Spider, at the distance whereto she has retired, be unable to take advantage of the windfall? Never fear. She arrives in a flash. How does she know what has happened? Let us explain the matter. It is the vibration of the web which tells her, rather than the sight of the captured object. To prove this, I laid upon several Spiders’ webs a dead Locust. I placed the Locust where the Spider might have plainly seen it. Sometimes the Spider was in her web, and sometimes she was outside, in her hiding-place. In both cases, nothing happened at first. The Spider remained motionless, even when the Locust was at a short distance in front of her. She did not seem to see the game at all. Then, with a long straw, I set the dead insect trembling. That was quite enough. The Banded Spider and the Silky Spider hastened to the central floor, the others, who were in hiding, came down from the branch; all went to the Locust, bound him with tape, treated him, in short, as they would treat a live prey captured under the usual conditions. It took the shaking of the web to decide them to attack. If we look carefully behind the web of any Spider with a daytime hiding-place, we shall see a thread that starts from the center of the web and reaches the place where the Spider lurks. It is joined to the web at the central point only. Its length is usually about twenty-two inches, but the Angular Spider, settled high up in the trees, has shown me some as long as eight or nine feet. <div class="figcenter"> <ANTIMG src="images/i_244.jpg" alt="" /> “The slanting cord is a telegraph wire.” </div> This slanting line is a foot-bridge by which the Spider hurries to her web when there is something going on there, and then, when her errand is finished, returns to her hut. But that is not all it is. If it were, the foot-bridge would be fastened to the upper end of the web. The journey would then be shorter and the slope less steep. The line starts from the center of the net because that is the place where the spokes meet and therefore where the vibration from any part of the net is best felt. Anything that moves upon the web sets it shaking. All then that is needed is a thread going from this central point to carry to a distance the news of a prey struggling in some part or other of the net. The slanting cord is not only a foot-bridge: it is a signaling-apparatus, a telegraph-wire. In their youth, the Garden Spiders, who are then very wide-awake, know nothing of the art of telegraphy. Only the old Spiders, meditating or dozing in their green tent, are warned from afar, by telegraph, of what takes place on the net. To save herself from keeping a close watch that would be drudgery and to remain alive to events even when resting, with her back turned on the net, the hidden Spider always has her foot upon the telegraph-wire. Here is a true story to prove it. An Angular Spider has spun her web between two laurestine-shrubs, covering a width of nearly a yard. The sun beats upon the snare, which is abandoned long before dawn. The Spider is in her day house, a resort easily discovered by following the telegraph-wire. It is a vaulted chamber of dead leaves, joined together with a few bits of silk. The refuge is deep: the Spider disappears in it entirely, all but her rounded hind-quarters, which bar the entrance. With her front half plunged into the back of her hut, the Spider certainly cannot see her web; she could not even if she had good sight, instead of being half blind as she is. Does she give up hunting during this period of bright sunlight? Not at all. Look again. Wonderful! One of her hind-legs is stretched outside the leafy cabin; and the signaling-thread ends just at the tip of that leg. Whoever has not seen the Spider in this attitude, with her hand, so to speak, on the telegraph-receiver, knows nothing of one of the most curious examples of animal cleverness. Let any game appear upon the scene, and the slumberer, at once aroused by means of the leg receiving the vibrations, hastens up. A Locust whom I myself lay on the web gives her this agreeable shock, and what follows? If she is satisfied with her prey, I am still more satisfied with what I have learned. One word more. The web is often shaken by the wind. The signaling-cord must pass this vibration to the Spider. Nevertheless, she does not leave her hut and remains indifferent to the commotion prevailing in the net. Her line, therefore, is something better than a bell-rope; it is a telephone capable, like our own, of transmitting infinitesimal waves of sound. Clutching her telephone-wire with a toe, the Spider listens with her leg; she can tell the difference between the vibration proceeding from a prisoner and the mere shaking caused by the wind. <div></div> <div style="break-after:column;"></div>

1 of 2

2 of 2