Part 12

They are called May flies because they often come out in the month of May, though sometimes not until June, and some species are as late as July in appearing.

We shall have to look into the ponds and little streams to discover where they come from.

See, John has scooped up some little speckled grubs out of the mud. Is it possible that they are the larvae of our fairy May flies? They have a mouth!--see what big jaws for such little creatures.

And what do you suppose they eat?

No doubt they, too, live on animal food.

No doubt they move about in the mud and catch what they can.

You see, John had to dig them up; they like to burrow in the weeds and mud, and some of them even make tunnels of mud 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!

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 the May fly, like a winged fairy from a prison cell.

They do not come out slowly and wait for their wings to dry like the dragon fly.

They spring out all of a sudden and fly away, leaving their cast-off skin in the pond.