Nature has provided spiders with an organ filled always with liquid which, on being exposed to the air, hardens, and can be drawn out into the slender threads we know as cobwebs. The silk-worm encases its body with a mile or more of gleaming silk, but there its usefulness is ended as far as the silkworm is concerned. But spiders have found a hundred uses for their cordage, some of which are startlingly similar to human inventions. Those spiders which burrow in the earth hang their tunnels with silken tapestries impervious to wet, which, at the same time, act as lining to the tube. Then the entrance may be a trap-door of soil and silk, hinged with strong silken threads; or in the turret spiders, which are found in our fields, there is reared a tiny tower of leaves or twigs bound together with silk. Who of us has not teased the inmate by pushing a bent straw into his stronghold and awaiting his furious onslaught upon the innocent stalk! Footnote 2: From Beebe's _The Log of the Sun_, by permission of Henry Holt Company. A list of all the uses of cobwebs would take more space than we can spare; but of these the most familiar is the snare set for unwary flies,—the wonderfully ingenious webs which sparkle with dew among the grasses or stretch from bush to bush. The framework is of strong webbing and upon this is closely woven the sticky spiral which is so elastic, so ethereal, and yet strong enough to entangle a good-sized insect. How knowing seems the little worker, as when, the web and his dew of concealment being completed, he spins a strong cable from the center of the web to the entrance of his watch-tower. Then, when a trembling of his aerial spans warn him of a capture, how eagerly he seizes his master cable and jerks away in it, thus vibrating the whole structure and making more certain the confusion of his victim. What is more interesting than to see a great yellow garden-spider, hanging head downwards in the center of his web, when we approach too closely, instead of deserting his snare, set it vibrating back and forth so rapidly that he becomes a mere blur; a more certain method of escaping the onslaught of a bird than if he ran to the shelter of a leaf. Those spiders which leap upon their prey instead of setting snares for it have still a use for their thready life, throwing out a cable as they leap, to break their fall if they miss their foothold. What a strange use of the cobweb is that of the little flying spiders! Up they run to the top of a post, elevate their abdomens and run out several threads which lengthen and lengthen until the breeze catches them and away go the wingless aeronauts for yards or for miles as fortune and wind and weather may dictate! We wonder if they can cut loose or pull in their balloon cables at will. Many species of spiders spin a case for holding their eggs, and some carry this about with them until the young are hatched.