ud in which to protect their
soft bodies. Their short, stout legs enable them to dig well.

Their bodies are soft, but their jaws are not. O dear, no!

[Illustration]

The grown-up May flies mate, and then the female drops her eggs on the
surface of the water. When she does this a fish will very often jump up
and seize her, for fish are very fond of May flies, and lucky are the
May flies to escape these ravenous enemies.

The eggs are heavy and sink to the bottom, where they hatch into these
queer-looking larvae that eat and grow and shed their skin just like the
dragon fly larvae.

Those brushes along their sides are the gills they breathe with.

See the gills moving swiftly back and forth; they look as though the
larva wished to swim with them, but this is not why it moves them so
constantly.

The continual motion of the gills stirs up the water and keeps our larva
supplied with fresh air.

Nellie is asking what gills are.

Well, gills in fishes and in such insects as have gills, and in crabs
and lobsters and other creatures that live in the water, are parts that
often look like fringes or flat plates.

The gills of fishes have a great many blood vessels running through
them. The walls of these blood vessels are very thin, and the oxygen
from the air that is in the water passes into the blood that is in the
gills, and then this blood, all full of oxygen, circulates through the
fish's body.

You see in fishes the blood vessels come into the gills and get the
oxygen.

In insects it is different. There are air tubes running like tiny pipes
all through the gills and into the body of the insect. The oxygen of the
air that is in the water passes out through the walls of these tubes
into the blood of the insect.

Yes, John, in fishes the blood comes to the air, in insects the air goes
to the blood. The air passes into the air tubes of the insects, and thus
is carried all through their bodies.

The blood takes the oxygen out of the air.

Without oxygen in the blood no animal could live.

Now let us go back to our May flies. They remain in the larval state a
year, and some species remain two years. Think of living in the mud for
two long years!

In the mud they creep about, eating, eating, eating. Then some summer
day they leave the mud and swim to the surface of the water.

Pop! they are gone.

They were so quick about it we could not see what happened.

The larval skin burst open and forth leaped t