The first and easiest of all the small water folk for people like the Imp and the Elf to find are the caddisworms. Do you know a stonefly when you see one? A long brown-winged dirty-looking fly; you must often have seen one skimming along a brook, and settling on the pebbles that the water has left partly dry. A caddisworm is the thing that is some day going to be a stonefly, just as caterpillars are one day going to be butterflies or moths, and just as Imps and Elves are some day going to be grown-ups. That is all very well. But it does not tell you what a caddisworm is like. This is how the children find one. They paddle to a shallow part of the stream, where it flows under grassy banks, a place where the bottom is a little muddy, instead of being covered with small round pebbles. Then they stand and look into the water, up stream, for the ripples flowing from their ankles make it impossible to see into the water clearly if they look the other way. Then, searching carefully over the bottom, they look for anything small that moves. Presently they see something. It may be a little bundle of tiny sticks, or some pieces of dead grass, or a couple of irregularly shaped twigs, moving crookedly over the sand or mud. And they know that they have found a caddisworm. One or other of them, usually the Imp, dives a hand down into the water and catches it, which is very easy to do, for caddisworms are leisurely people, and do not move much faster than snails. It is lifted out of the water and held out, looking like a little bundle of sticks in the palm of his paw. But while we watch something comes jerkily out of the end of the bundle--a black head and six busy legs, and soon the caddis is crawling along as fast as it can, dragging its house behind it. For the bundle of sticks is really a log house that the caddis has built for itself. He builds it about his own body all round him, adding stick by stick in the neatest, cleverest manner. He builds with anything he can find, and it is often possible to make him a present of a twig, and see him use it up as a new log in the walls of his house. Nothing comes amiss to him. If the stream he lives in is full of little snails, he is quite ready to cover his home with their shells. Beads, twigs, pieces of grass cut short, flat seeds, scraps of paper, anything you can think of, he will somehow manage to make useful. The odd part of it is that instead of bringing the bricks to his house, or the logs, or whatever you like to call them, he goes in his house to look for each brick, and, when he has finished his building, he carries his home about with him.