Mary Adrian, The mystery of the night explorers, New York, Hastings House, 1962.
« If you think they’re something, » continued Jimmy, « wait until you see a caddis worm. He has his own submarine. » Jimmy began looking for a tiny bundle of sticks in the brook. He finally found one floating near the bank.
« Here’s a caddis worm, Randy, » he called.
« That’s his house, » explained Jimmy. « He builds it to protect himself from enemies, but it’s really his submarine. I’ll show you. » Jimmy reached under water and picked up a pebble. He threw it near the place where the caddis wormaws floating. Immediately the tiny creature dropped to the bottom of the brook.
Randy could hardly believe his eyes. “Boy! I’ve never seen anything like that. How did he do it?” “He pulled his head into his house,” replied Jimmy
« When the caddis worm wants to float, he sticks his head out of his house. This leaves an empty space in the back that fills up with air, and the caddis worm is able to float.It’s just as if a life preserv was holding him up. When he wants to go under water, he draws in his head. This makes his house heavier, and presto ! down he sinks to the bottom like a submarine. »