When winter comes the worms plug up the doors of their houses. This is done by dragging into the doorway a plant stem that will fit and fill it. The worms carry into their homes leaves and stalks to eat. They bring out, and throw away, things which they do not like. Worms show much sense in the way in which they carry things in and out of their holes. If a stem will not go in, they turn it over, and try it in some other way. [Illustration: Mr. Worm at Home.] Worms usually come out of their holes at night or in wet weather. If they go far from their house, they cannot find their way back. Then they make a new hole. Each worm lives alone. Often in the evening or early morning, or during rain, you will see worms near their houses. You may find them with their heads just put out of their doors. You will see the worm casts in early day or after rain. It is then the worms dare to come out. Sun and heat dry worms up very fast, and so kill them. [Illustration: Mr. Worm leaving Home.] The birds know all these ways of the worms. Watch a robin or a bluebird. He searches for his food at sunrise, or after sunset, or while it rains. Now his keen eyes see the worm at his door! In goes his sharp bill! He pulls like a good fellow! He is hungry. He wants his breakfast. The worm holds fast by his hooks. The bird braces his feet and his tail, and tugs hard. Out comes the worm to feed Mr. Bird.[13] The bird shows great skill in the way he pulls the worm out of the hole. He does not break off even one little bit of his soft body. No boy could get him out in that way. Some say that the worm lies by his door at sunrise for warmth. I do not think that is so. I think what he likes is the fresh dew. He loves dampness. He fears cold, but he also dies of heat. Any worm will die in one day in dry air, but some kinds of worms will live for weeks quite down under water. He needs an even, moist warmth. His home must not be hot, nor cold, nor dry. Little young worms know how to dig houses, make worm-casts, carry out the soil, find food, and plug up the door of their houses. They know at once all that old worms do. But then worm houses do not require as much skill as bee or wasp houses. The seaside worms make the prettiest houses. On shells, stone, wood, or wound alone in a lump, you will find their tubes. They are white and as hard as shell. Inside they are pink or blue. These tubes curve and twist about, as the worm went that built them. Some are very pretty. There is a soft kind of tube made of sand and bits of shell, stone, and weed. The sand and weed are held together by a kind of glue. The worm makes this glue in its mouth. I have some tubes very clear and white. You can see the lines where the worm went when he built them, ring by ring. Some of these tubes are so small you can just run a fine needle into them. Some are as large as a straw, and some as large as a fine fat earth-worm.