These great spiders of the tropics hunt for prey in much the same way. Only instead of catching flies on walls they prowl about the branches of trees in search of small birds, springing upon them when they are roosting at night, and killing them almost immediately by a smart bite from their venomous fangs. These spiders, of course, are very large. Indeed, the body of a full-grown bird-spider is as big as a man's fist, while its great hairy legs cover nearly a square foot of ground when they are fully spread out. TRAP-DOOR SPIDERS These famous spiders are found more or less commonly in all warm countries. They all live in tunnels in the ground, which they dig by means of their fangs; and as they do not want the situation of their nest to be discovered, they carry the earth away to a little distance as fast as they dig it up, and carefully hide it. Very often the hole which they dig in this way is eighteen inches or two feet deep. And at the bottom it always turns sideways for an inch or two, so that the general shape of the burrow is very much like that of a stocking. This hole is always dug in the side of a bank, so that when there is a heavy fall of rain the water may run away without flooding it. When the burrow is finished, the spider lines it throughout with two sheets of silk. The outer sheet, which comes next to the earth, is rather coarse in texture, and is quite waterproof, in order to keep the tunnel dry. The inner one is very much finer and softer, so that the little home may be as comfortable as possible. As soon as the lining process is completed, the spider sets to work on the trap-door. This she makes in the cleverest manner possible. First she measures the doorway most carefully by the aid of her feelers. Then she spins a thin silken pad of exactly the same size and shape. This is sticky on the top, like the spiral thread of the web of the garden-spider: and she sprinkles it all over with very small scraps of earth. Upon this she fastens another silken pad, which she sprinkles with earth in the same way. And then comes another and then another, and so on till the door is sufficiently thick. Finally, she fastens it in position by means of a hinge, which is also made of silk; and she always places this hinge on the upper side of the doorway, so that the door may fall down behind her by its own weight whenever she leaves the burrow. She is rather a lazy creature, you see, and does not want to have the trouble of shutting the door for herself! And if she left it open, every passer-by would find out where she had made her home. The door always fits most wonderfully into its place, and the spider carefully covers the top with little bits of moss and small scraps of earth and stone, so as to make it exactly like the surface of the ground all round it. Indeed, unless one happens to see the spider push it open, it is almost impossible to find it.