Edith M. Patch, First Lessons in Nature Study, New York, The McMillan Company, 1927, pp. 210-212.

When you lie down on a log or low plank bridge or a flat rock and look down into the shallow water, keeping quiet sa that you will not disturb anything, you will see queer little things moving about. The things seem to be made of stones or bits of sticks or rubbish, and so they are.

Such moving bundles of sticks and tubes of stones are interesting things to have at school or at home, if they are kept in plenty of fresh water. Each one has a young caddis Inside. It is a very good game to see how many different kinds of caddis cases you can find.
If you choose to find stone cases, you must hunt where the bed of the stream or pond is pebbly or sandy. Did you ever see a stained-glass window which is made of many small pieces of glass of different shapes fitted together into one big window ? There is a kind of caddis that takes little clear pebbles and glues them together so that they fit as well as the pieces in a stained-glass window. This sort of case is less than an inch long, and the pebbles used in it very tiny indeed .
The young caddis does all its building under water. Where do you suppose it gets its glue. There are some glands in the body of the caddis where the glue is made.