Margaret Warner Morley, The Insect Folk, vol. I, Boston, Ginn & Company, 1903, pp. 190-194.

The little caddice flies
Here we are in the wood again.
How sweet it smells!
Let us sit down by the brook and look into it.
It is such a clear little stream, with fine sand and little pebbles at the bottom.
What has Nell found that pleases her so?
She says she sees some little bars of sand moving about.
Ned says they are not sand bars but tubes of sand, containing a little live thing.
The truth is, this sand bag is a house, and its occupant is a larva.
See the black head come poping out, and the tiny fore legs.
The larva dies not come entirely out, you see, but pulls its house along with it, and when it is frightened it pops back into its little stone case.
Mollie says it reminds her of a hermit crab.
A hermit crab, you know, lives on the seashore and take possession of an empty snail shell for a house.
It comes partly out dragging its house with it, but if you disturb it, in draws back, sometimes quite out of sight.
This little larva lives in a house, too, but it is a house of its own making.
It is the larva of the caddice fly, or case fly.
Let us put one of these little sand cases in the saucer here.
Please fill the saucer about half full of water, John. Thank you.
Now, Mollie, I see you have picked up a fine big caddice case.
Put in the saucer, and let us watch the larva crawl about.
It never comes entirely out of the case, you see. It holds on to it with the hinder part of its body.
Its little black head is hard, but its body is soft, and that is why it does not like to expose itself to hungry larvae that migh be living in the water.
Mays says she wants to see the whole larva.
Suppose we carefully break away the little sand case.
No, indeed, little Nell, we are not going to hurt the larva; we are only going to open its house.
There, the larva is outside now, and you can see what a tender, pale little thing it is.
It does not like to have its soft body exposed.
See ! it is already gathering little bits of sand together.
It seems to be sticking them fast to its body.
It is really binding them together by a saliva-like substance from its mouth.
It draws out little glistening threads that Harden into silk as soon as they touch the water.
Queer saliva you think.
But the caddice larva does not fin dit queer. It is used to saliva that hardens into silk.
Yes, May, it papers its walls with silk.
You see it did not hurt the caddice larva to take away its house; it immediately went to work to build another.
Why not pull it out, instead of breaking its house to pieces?
Because if it had been pulled hard enough to come out, it might have been torn to pieces, it is such a tender litle thing, and it holds fast so tightly.
So the best way to remove it safety is to break its case bit by bit from around it.
I does no harm to break its case if one is careful. It will soon build another.
Yes, this larva has no distinct thorax. It is like th larvae of the dobson, the aphis lion, and the ant lion in that respect.
See! John has found one whose tube is made of quite large stones as compared with the tube of fine sand that we have broken open.
Some caddice larvae build houses of wood instead of stone. They stick little together, and some use little pieces of leaves.
Others again use tiny shells which, as you can imagine, make very pretty cases. Our little caddice has made a neat little house of fine sand grains very nicely put together.
Some others make much rougher houses.
You will be apt to find the caddice larvae in any brook and in some ponds, and I hope you will always look for them.
Notice the tracery in the soft mud of the brook.
Those lines that look as though some one had been ornamenting the bottom of the brook are made by our caddice larvae. They drag their cases along and thus make these lines. Sometimes such lines are made by the little fresh-water snails ; but you can always find the decorator by following along the lines he makes.