Uncle Philip’s, Conversations with Young Persons, New York, J. & J. Harper, 1833, p. 73-76.
There are several sorts of them, but the one I am thinking of now, builds a stone house to live in. These worms are in the habit of making a little tube, sometimes of sand, or shell, or wood, or leaves, or stones, to live in ; and their skill consists injoining these perfectly, and making them stick together. But we are talking now of the caddis-worm that uses stone. What the worm has to do is to make a tube out of small stones, that shall have a hollow about as large as a wheat straw, and be perfectly smooth inside. This is a pretty hard task- at least it would be very hard to us. When the stone-mason wishes a stone of a particular size or shape, and cannot fin dit, he takes his hammer and breaks one until i twill suit ; but the caddis-worm has no hammer, and must take the stones just as it finds them. The little insect then has to pick out a great many stones before he gets the right one, because they have so many little rough points about them that it is very difficult to get those which will make the tube perfectly smooth inside. Remember, too, that the bottom or lower side of this stone case has to be pretty nearly smooth, so that the worm can drag it along on the bottom of the spring or pond (for it never comes out of it), and you will see that the picking out of the stones alone is no trifle. But besides this, it has to fasten them together with mortar. »
« And can the worm really do this, Uncle Philip ? Will not the water wash the mortar all away ? »
« It certainly would if it were like common mortar. It was a long time that men lived before they found out a mortar that would remain, and grow hard under water. When they want to build a wall that is to be under the water, they use a cement which is called pozzolana ; it is made of lava cut of a volcano, and is water-proof. Our caddis-worm has a cement too, which is better than pozzolana, and though it has been tried, it can not be melted or dissolved in water. Here is a drawing of the stone nest of a caddis-worm. »
« Uncle Philip, you said that sometimes these worms built their nests of other things besides stones ; let us hear something of them if you please. »
« Very willingly, boys. Some build of shells : here are pictures of their nests. Some build of leaves, and others of pieces of reed or light bark.
And a curious thing about those which build of light pieces of bark or reeds in this, that they will make the top-piece come over so as to hide their heads, and prevent you from seing them. Some build of sand ; and then as the house would be so light that the water running from the spring might Wash it down and carry it away, the wonderful little creature takes care to anchor it by fastening a pretty large stone to it when it has nearly finished it.
And as the worm anchors it when it is too light, soi t lightens it when it is too heavy, by fiwing a bit of light wood or hollow straw to it to buoy it up. »
« Well this is truly a wonderful insect, Uncle Philip. »
« Truly so indeed, boys. In all these cases it uses its water-proof cement, and if you break its house to pieces, and will patiently Watch you may see it build another.