In one respect the Caddis resembles the larva of the Wax-moth, mentioned on page 151, inasmuch as it has a soft, defenceless body, while the first three segments are comparatively hard. Like the Wax-moth also, the Caddis lives in a tube constructed by itself. Instead, however, of having a long and fixed tube, up and down which it can pass at pleasure, the Caddis makes a tube only a little longer than its body, and light enough to be carried about, just as the hermit-crab carries its supplementary shell. There are many species of Caddis-fly. The Caddis inhabits fresh waters, and cares nothing whether they be ponds or running streams. In order to defend its white, plump, and helpless body from the fishes and other enemies, it constructs a tube around its body, strengthening it by a wonderful variety of material according to the locality. Mostly the tubes are covered with little pieces of stick or grass, or leaves, while some species use nothing but sand-grains, constructing with them a tube very much resembling in shape an elephant’s tusk, and reminding the conchologist of the dentalium shell. But they seem to use almost anything that comes to hand. Taking only examples found by myself in a single pond, these cases are formed of sand, stones, sticks, grass-stems, leaves, shells of small water-snails, mostly the flat planorbis, the opercula of the water-snail, empty mussel-shells, a chrysalis of some moth which had evidently been blown into the water from an overhanging tree, and acorn-cups. The larva, however, does not seem to be able to fasten together any objects with smooth surfaces, and though it has been known, when in captivity, to make its cases out of gold-dust or broken glass, it could not use either material when in the form of beads. When it is full-fed, and about to enter the pupal state, it proceeds to prepare its habitation. As a larva, when it desired to feed, it protruded its head and the front of its body from the mouth of the tube, and then crawled about in search of nourishment, dragging the tube with it, and holding it firmly by means of the claspers with which the end of the body is furnished. But when it becomes a pupa it is no longer able to defend itself, and is instinctively compelled to secure its safety in some peculiar manner. It cannot fasten up the entrance entirely, because it would not be able to breathe unless water could pass over its body. Accordingly, it constructs a grated window precisely like those of the old castles, so that water can pass freely, while no enemy can gain admittance. Unlike, however, the grated windows of the castle, which had no pretence to beauty, the Caddis always constructs its barriers in some definite pattern. Each species appears to have its own peculiar pattern, but all agree in making their window, if we may so call it, exactly like a wheel-window before the glass is inserted.