Frieda May Haworth, Pond Dwellers, Londres, University of London, circa 1960.
It is strange how they know just how to build and what material to use though they have never been taught. In the picture you can see some different kinds of house. Some caddis fasten long sticks to little tubes of sand. Others cut pieces of stick all the same length and arrange them criss-cross, making a shaggy-looking case. One in the picture is made of tiny shells, and there is a beautiful one made of bits of pondweed cut all the same size and arranged in a spiral pattern. It is interesting to watch the larva build the case. There is a spinning gland under its chin which makes a fine silk thread. Pieces of stick are fastened together with this silk to make a ring which is slipped over the head. More and more sticks are added in front until a tube, open at both ends, is formed. It is lined with silk.