With this little twig let us carefully brush away the white froth.
Now see.
Yes, there is something in the centre of it.
It is the larva of a—bug!
The female bug, and here is one of the little things, lays the egg on the leaf or twigs, and when it hatches the young bug sucks out the sap of the plant which finally appears as this white froth.
The larva remains surrounded by the froth until its transformations are complete.
Just before the last moult it stops sucking out sap. The froth dries about it in the form of a little room, and in this it undergoes its last moult and comes out—an adult bug.
The froth is supposed to be used as a protection, and it may be against some enemies, but there are certain wasps that delight in invading the frothy masses and hauling out the unwilling morsels within to feed to their young.
No, little Nell, the frogs have nothing whatever to do with this frothy substance which was called frog spittle before people understood about the little insect that made it.