Some are square

Leonora et Arthur HornblowInsects do the strangers things, New York, Books  for Young Readers, Random House, 1968.

A young caddisfly is called a caddis-worm. It hatches underwater. It makes a tube of silky stuff. On this it builds its house. It uses sticks or sand or leaves or little stones. Some caddisworm houses are round. Some are square. One caddisworm make a house that look like a snail shell.