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Brian J. Ford, The secret language of life: how animals and plants feel and comminicate, New York, Fromm International, 2000, p. 135.

The caddis fly insects have a wide range of finely developed senses, and can undertake surprising tasks. The caddis-fly larva constructs a house for itself out of inert materials it seks out on the sandy bottom of the water in which it lives. Many of them can be recognised by a fondness for one particular kind of constructional element, whether tiny stones or fragments of plant stems. The larva starts with a tiny case of particles held together with silk which it secretes. The first case often has a hinged door at the front, which can be closed when necessary, and is often a single piece of leaf or large grain of sand. As the larva grows, it adds to its home. You can watch them scurry around the bottom of a pond or streams, looking for the particles they prefer. Some of them cut front the leaves of water-plants segments of a carefully controlled size using their specially adapted mouth-parts. Sometimes as larva will take over an empty case, and adapt it for its own use.