Ross E. Hutchins, Nature Invente It First,  New York, Dood, Mead & Company, 1980, p.84.

The pebbles used by the caddises are nicely fitted together and their cases protect them against most ennemies, such as fish. They apparently prefer colorful pebbles to making their case, since they usually select the brightest kinds found in the stream where they live. Fragments of red garnets, black obsidian, and bits of opal have been used in caddis cases. In the Teton Mountain of Wyoming I found a caddis case built of white quartz pebbles one of which contained a bit of shinning gold.

Caddis insects are not considered to be intelligent animals. Yet the cases they construct are well built and serve to protect the larval caddises from hard. Like all insect, they work from instinct or inherited knowledge. Man has learned to build all kinds of homes and buildings, but is he any better at it than the caddis insects ?

Wood has been used by man for building many things. Indians made tepees of sapling, pionners built log cabins. Bar kwas used for canoës, and tree trunks for dugouts. But human are not well equipped to carry out many construction projects without special tools. Today’s carpenter needs saws and hammers, nails and screwdrivers, and even special Tools like a carpenter’s level, a carpenter’s  square, a carpenter’s clamp.