Part 68

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 popping out, and the tiny fore legs.

The larva does 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 takes possession of an empty snail shell for a house.

It comes partly out dragging its house with it, but if you disturb it, it 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 it 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 might be living in the water.

May 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 find it queer. It is used to saliva that hardens into silk.