The caterpillars climbed serenely into the brush arches above their heads, selected spots that pleased their fancy, and began constructing their cocoons. First came the loose, web-like oval within which the cocoon itself was to be made. This was the work of the first day and its construction was of what is known as floss. Then followed the yellow, compact cocoon requiring three or four days for its spinning. Occasionally two worms would insist upon spinning together, crossing and recrossing their threads; these double cocoons always had to be sorted out from the others, however, as the silk could not be wound off them easily. The spinning was an interesting sight. The silkworms poised themselves on the lower extremity of their bodies and using their front legs to guide the thread, sent it hither and thither from their mouths in wavy, irregular motion until the little egg-shaped ball was finished. The two fibres from the right and left side of the worm were so perfectly united in the spinaret that it was impossible to detect more than one thread. Patiently the tiny spinners toiled, and those worms that failed to spin were put into a room by themselves where the temperature was graded to a higher degree of heat that the warmer atmosphere might stimulate them to work. When at last the cocoons were done the Brettons surveyed them with satisfaction. The weeks had been busy, fatiguing ones with hastily snatched meals, and interrupted slumbers. "One could not keep on like this for a long stretch without more help," declared Madame Bretton. "I am glad the caterpillars have their houses made!" "They are better houses than you think, too," added Josef. "For each silkworm has coated the inside of his little home with a gum-like substance that makes it waterproof. He has no intention of lying down to sleep in a leaky cottage where the rain may drip through." "But there is no rain in here," objected Marie. "Of course not. But the silkworm does not know that. He builds his house just as he would if it was out-of-doors where the good Lord intended it should be. Your caterpillar hasn't the wit to realize that conditions have changed with the years, and that he now lives out his days beneath a roof that does away with the need of water-proofing. It is because the cocoons are thus sealed on the inside that the water does not penetrate them when they are floated. You'll notice that if you ever have a chance to see the silk reeled off. It protects the chrysalis until it pierces its way through its silken house and comes out a moth. But of course we shall not let ours do that." "Why not?" inquired Marie.