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 larvæ 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.