  “Look here, boys,” said Uncle George, “you have been paying nearly all your attention to the larva cage during my absence, and have forgotten the caddis worms.”
Uncle George made believe to be cross. “We changed the water every two days,” said Frank. “Yes, I know. But you have not reported any changes in the creatures themselves. What has been going on in the larva cage has also been going on here in the water, for caddis worms are simply water-caterpillars. Uncle George laid three saucers on the table, and continued:— “We are going to look into the life of the caddis fly to-day; but before I take them out of the water, I want you to tell me what you have noted about them up to now.” “They are always climbing up the water weeds,” said Frank. “They are always adding to their cases,” said Tom. “Some of them have died,” said Frank. “What?” said his uncle. “Do you mean these at the bottom of the tank? These are not dead, they are only asleep. Put your hand in, and take some of these out.” “Their cases are stuck to the pond weeds and to each other,” said Frank, as he lifted a few out, and placed them in a saucer. “Ah, I have it, Uncle George! They have gone into the pupa state. Is that not so?” Uncle George nodded. “Look!” exclaimed Tom. “There are things like earwigs floating on the water.” “Never mind these just now, Tom,” said his uncle. “I am coming to them by and by. Observe the wonderful cases which the caddis worms have made for themselves. “Here is one whose case, when we found him, was made of neatly cut pieces of water rush. He has almost doubled the length of his case since then; for “He has got a fine collar of green pieces round his neck,” Frank observed. “Why are they always adding to the length of their cases?” asked Tom. “Because they are always growing,” said Frank. “That is the reason,” said Uncle George; “and they grow so fast that they have actually to work hard at building. “Observe those that make their cases out of tiny shells and stones. They have made free use of the coloured beads and small pieces of coal which we put in.” “How do they manage to stick these things together?” asked Tom. “A caddis worm is a busy creature,” his uncle replied. “He does two things besides eating and growing. With those strong pincers, which you see at his head, he saws off pieces of weed. “Near his mouth he has got a kind of loom for spinning silk. These pieces are stuck together with silk, which is a gluey substance when it first comes from the creature’s body. “These rough cases are lined with silk.” “Why does he have to make a house for himself, and carry it about with him?” said Frank. In answer to this, his uncle took out a few of the active caddis worms, and placed them in a saucer with water. He held one up. “You see,” he said, “his case is open at both ends. Now, if I tried to get him out from the front, As he spoke, Uncle George pushed the head of a pin into the tail end of the case, and the creature scrambled out at once. “It is too bad turning you out of your cosy room, Mr Caddis,” Uncle George observed; “but you’ll go back again as soon as you get the chance, won’t you? I want my nephews to understand why you work so very hard. “Now, Frank, you can answer your own question, I think—‘Why does the caddis worm build a house?’” “Because he has a soft body.” “Quite right. But why is he forced to protect his body?” “Fishes would eat him.” “Right again, Frank. If trout could speak, they might tell you that the sweetest morsel in the stream is the caddis worm. Now, take your lens, please, and tell me something about him.” “His body is divided into rings, and there are the same number of them as we found in the caterpillar.” “Very good, Frank. Now give Tom a chance.” “His head and the first three divisions of his body are hard cased. They are black and yellow in colour.” “He has six legs,” said Frank, “and they are attached to the first three divisions of his body.” “What about the last division of his body?” Uncle George asked. “Oh, how funny!” said Frank. “It is divided into two large things like horns.” “These,” said his uncle, “are the hooks by which he fixes himself so firmly in his case.” “And what are all these curious big bristles for?” asked Tom. “They are all over his body.” “These are his breathing organs,” Uncle George answered. “The caterpillar, if you remember, had breathing-holes along the sides of his body. By moving his long body, the caddis worm causes a constant current of water to pass through his dwelling. “Look at the fourth segment of his body. How does it differ from the others?” “It is the broadest segment,” said Frank, “and there is a stout rounded thing in the middle of it.” “Yes,” his uncle replied, “and if we can get him turned on his back we shall see two more of these stout outgrowths below, one on each side of the same segment. This is really very clever. By it the animal keeps himself in the middle, so that the current of water must flow all around him. “Now, look at the case of a sleeping caddis.” “The front of the case is closed,” said Frank. “How is it closed, Frank?” “Well, there is a network of threads over it,” answered Frank. “Yes; you see a caddis worm cannot do without fresh water, even when he is asleep; so, before going to sleep, he builds a grating over the entrance. “When he wakes up, he has quite a new shape altogether. And this brings us to those things which Tom said were like ‘earwigs.’ There are five of them floating on the water, and two of these are dead. If “How does he get out of the case?” inquired Tom. “Easily enough. Look at the strong pair of pincers he has got for cutting his way through the silken grating with. No longer burdened with his heavy case, he floats up to the surface. He crawls up out of the water into the air. “If there are no rushes or floating leaves about, he is sure to drown; for your caddis is no longer a water insect, but a fly inside a thin skin. “Now, boys, I am going to show you something wonderful.” Uncle George then took out the three living pupÆ that were floating on the water, and placed them on the table. The boys watched them for a long time. They were beginning to get impatient, when suddenly the skin of one of the creatures burst along the back, and a lovely little fly, with brown, gauzy wings and long feelers, came out. After airing its wings for about a minute, it flew to the window. The other two acted in just the same way. “Now, my dear boys, I think you know something about the life of the caddis fly. For a whole year of his life he is a crawling water insect, then, for about a single day, he is a lively fly.” “How does the caddis larva first get into the water?” asked Frank. “As an egg, Frank. The female caddis fly lays her eggs in the water. She sometimes even crawls down right into the water to lay them. “A tiny caddis grub, no bigger than this pin-head, comes out of each egg. As soon as he hatches out, he begins to build his case, to eat, and to grow; and from the moment of his birth up to the closing up of his tube, he is scarcely a moment idle.” Exercises on Lesson XIV.
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