"It changes its skin a good many times, and sometimes it looks a little better while the skin is still clean and light gray. But it soon turns dingy again. See these three little leaf-shaped gills I've drawn?"
"They are like the screw on a steamer," commented Jimmie.
"They are, a little. Well, this chap uses these gills for the same purpose as the steamer uses its screw—to scull through the water."
"What happens when it changes?" asked Jack.
"After the nymph has its full growth, some sunny morning soon after daylight, it makes its way up out of the water on to a stem and waits quietly for the old dark skin to split. Then out crawls a soft-skinned creature with gauzy wings. But the body is so moist and weak it has to wait awhile for the warm sunshine to harden the skin and strengthen the muscle. When this is done the new dragon-fly, with its glistening body, flies out from the pond in the bright, warm light."
"Then does it live forever?" asked Betty.
"No; it dies after twenty-five to forty-five days of its flight. Here, Jack, catch that fellow!"
There was a wild scramble, but every time Jack just missed the dragon-fly. Finally Betty lent him her broad hat, and at last Jack caught the insect.
"Gee! aren't its eyes big?"
"And beautiful, too," said the guide. "They are made up of thousands of facets (a facet is just a small, plain surface) as many as thirty thousand facets in one eye. Some look up, some look down, some look out, some look in; so that there is nothing that escapes the sight of this hawk of the air. Look at the wings on this fellow, and look at the picture I drew for you of the nymph. Well, this fellow's wings begin in the nymph as tiny sacs, or pads, made by the pushing out of the wall of the body. Running all through between the two layers of the wing are thickened lines of chitin, which divide and subdivide, forming this fine network. In the new wing, protected by these thickenings, are air-tubes, which divide and branch into all parts of the wing. But as the wing reaches its full growth most of the air-tubes die." The guide paused. "We are talking too much and fishing too little. Time to go on. Put out the fire, boys. Be sure that it's out. Run water all around it. Now we're off!" And up, up, up the brook they went.