Uncle George had to go from home for a week, and his two nephews went part of the way to the railway station with him.
As they were about to take a short cut through the wood, Uncle George went up to a huge beech tree. He looked very closely at its grey trunk for a time, then stepping back from it about three yards, exclaimed:—
“Come here boys! Stand beside me, look closely at this tree, and tell me if you see any strange objects sticking to the bark.”
After staring at it for some time, they both declared that they could see nothing upon it.
“Go nearer—nearer still! Now, do you see anything?”
The boys shook their heads.
“Go quite close up to the trunk and examine it,” said Uncle George.
“Oh,” said Frank suddenly, “I see queer things like grubs, coloured almost exactly like the bark. Some of them are lighter in colour.”
“Look carefully at those lighter ones, and you will find that they are just empty cases.”
“So they are,” said Frank, as he touched one with his finger and saw it crush up.
“Notice how they are fixed to the bark!” said Uncle George.
The boys watched as their uncle placed his pencil under one of the darker coloured objects, and saw that it was slung up to the tree by a loose silken girdle round its middle, while a tuft of fine threads fastened the lower end to the bark.
Suddenly, as if it were annoyed at being touched by the pencil, the lower half of the object moved from side to side with rapid jerks.
“Why, it is alive,” said Tom.
“Yes, of course it is,” said his uncle. “This is another lucky find.”
“What are they?” Frank asked.
“Can’t you guess, Frank? Don’t you remember my telling you that all the insects were asleep in their cases during winter.
“Each of these darker coloured cases contains a white butterfly. They have been here all winter, and they are just about to hatch out.”
“How do you know that, Uncle George?”
“I know it because the empty cases tell me that some of the butterflies have just hatched out. This is what your cabbage caterpillar becomes after he is tired of feeding.
“You have now seen three different stages of the life of this insect. First, the curious eggs laid on the under side of the cabbage leaf; next the greedy caterpillar; and now, the chrysalis orpupastage.
“The caterpillar goes to sleep in autumn as a hard-cased chrysalis, and wakes up in spring a beautiful butterfly.”
“How strange,” said Frank. “And will our caterpillars remain caterpillars until autumn, and then tuckthemselves up like this and go to sleep for the winter.”
“No, Frank! our caterpillars will go into the chrysalis state in a week or so, and hatch out as butterflies in August. These August butterflies will lay eggs. The caterpillars from these eggs will turn intopupæin September.
“These September pupæ will supply the white butterflies of next spring and summer. Put some of these into your box. Watch then carefully, and you may be lucky enough to see the white butterfly coming out of his winter case.”
“I cannot understand,” said Tom, “how a big white butterfly can be inside so small a case. It must be very tightly wrapped up.”
“So it is, as you will see,” said Uncle George. “Good-bye, boys! and mind, when I come back, I shall expect to see notes and sketches of all that has taken place in the larva cage during my absence.”
* * * * * * * *
“Won’t you let your uncle take his dinner first,” said Frank’s mother, as she hung Uncle George’s overcoat up in the hall.
“No, mother! he must come at once,” said the excited Frank. “There’s a butterfly just coming out.”
“Oh, I must come and see that,” said Uncle George; and he allowed his eager nephews to drag him towards the larva cage.
By the time they got to the cage the butterfly had hatched, but they were in time to see it unfurl its wings. The wings were crumpled and twisted, but the creature slowly straightened them out to dry in the sun.
“We saw it burst its case,” said Tom. “First a small slit appeared at the head end. This slit grew larger. Then the butterfly’s head and feet appeared. It squeezed its way and was just half way out, with its wings crumpled round it, when you arrived.”
“I arrived just a minute too late, then,” said his uncle.
White or Cabbage Butterfly and Pupa.
White or Cabbage Butterfly and Pupa.
“Oh, and the eggs have hatched too,” said Tom. “Look at them now, Uncle George!”
His uncle looked, and saw that the white patches of eggs had given place to larger patches of little active, dark coloured maggots.
“We want to know what has become of the lovely carved shells of the eggs,” said Tom.
“They have been eaten up,” his uncle replied. “From the moment a caterpillar is born he does nothingbut eat—eat—eat. He begins by eating the shell of the egg he comes out of.
“For the first week of their lives these tiny caterpillars feed together in small bands, and they grow so fast you can almost fancy you see them growing. After they have grown to a certain size, each caterpillar starts out for himself.”
“Do you see the three butterflies that have hatched out?” asked Tom.
“Yes, I see them. There are two females and one male,” said Uncle George.
“How can you tell males from females?” asked Frank.
“Oh, that is easy enough,” Uncle George replied. “The females are larger, and have two big black spots on each of their front wings. But I only see eight of the large cabbage caterpillars. We put in twelve, I think.”
“Look!” said Frank, pointing to the roof of the cage.
“Ah, yes, I see them. Two of them have passed into the pupæ stage, and are slung up by their silken belts to the wall of the cage.
“The other two are spinning silken belts round the middle of their bodies, if they have not already done so. After this belt is finished they will slowly slip their useless green skins off, and finally get rid of them by sharply jerking the tail end of their pupa cases.”
“Yes, we watched those other two do that,” said Tom.
“Notice,” continued Uncle George, “that all your big cabbage caterpillars have lost their yellow stripesand are now of a bluish green colour. They have stopped feeding, and are now dull and sleepy. This indicates that they are about to enter the pupa stage.”
“But look at the currant and the hairy caterpillars, uncle,” said Frank.
“My dear boy,” said Frank’s mother, “Uncle George must really have food and rest after his long journey. He will hear about the other caterpillars some other time.”
“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.”
1. Caddis Cases.2. Larva out of Case.3. Pupa.4. Caddis Fly.
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.You nearly missed something of very great interest.”
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; forsee, the front half is made of cut stalks of water weed neatly arranged.”
“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,I should never manage it. This is the way to get him out.”
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. Ifyou look, you will find five empty caddis cases in the tank.”
“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.”
BUDS.—Twigs of beech, horse-chestnut, lilac, and hawthorn ought to be taken in in December and placed in water. They should have as much warmth and light as possible.
Willow twigs (for catkins) might also be forced in this way.
SEEDS.—Seeds should be soaked for twenty-four hours and then sown in sawdust in boxes 4 inches deep. They should be sown in presence of the pupils.
In winter these boxes should be kept on the hot pipes in school. The sawdust should not be allowed to get dry, neither should it be deluged with water, but kept evenly moist if possible.
Be careful to use waternot colder than the temperature of the roomin which the seeds are grown. Nothing checks growth more effectively than chilling with icy-cold water. It is a good plan to keep the watering-pan full of water near the hot pipes, refilling it always after use.
Seeds germinate best in the dark, but whenever the plumule shows above the sawdust, the box containing them should be placed in the light. Sufficient seeds should be sown at one time to supply a plant to each pupil once a week for at least four weeks. A number of seeds or plants should be dug up once a week and sketched by the children. Each sketch should be compared with that of the previous week, and all changes duly noted down.
The best seeds to grow are:—Broad bean, common or “large white” maize, runner bean (“Painted Lady”), French bean, kitchen pea (“Stratagem”), and white mustard.
A few seeds of white mustard should be sprinkled on a small piece of moist blotting-paper, and covered over by a small glass bell-jar or an inverted tumbler. In less than a week the root-hairs may be seen.
If hot-water pipes are available, the following seeds should be grown, as their germination is interesting:—date stones, walnuts, chestnuts, almonds, cherry stones, orange pips, seeds of cucumber and sunflower.
After maize and bean (or pea) plants have reached the height of 5 inches, they should be transferred to bottles of tap water—as described at the end of Lesson VI.—and the continuous growth sketched and noted from week to week.
POND AND DITCH HUNTING.—Make a ring of stout brass wire about 8 or 10 inches in diameter, and to this attach a bag net made of mosquito netting not more than 9 inches deep. In making the wire ring, leave attached to it about 5 inches of the twisted ends of the wire. Such a net as this can be easily carried and quickly attached to the end of a walking-stick by means of a piece of string.
The best “finds” are often made by sweeping the net under banks and among pond weeds.
FROG SPAWN.—Frog spawn is abundant in ponds and ditches everywhere in March. It should be kept immersed in as much water as possible in a large vessel, preferably of glass. Whenever the water show signs of fouling, it should be changed; but, as changing water containing tadpoles is somewhat difficult, the fewer changes the better.
As in the case of seed growing, the development of the tadpole should be learnt by weekly sketches and notes.
NEWTS.—Newts can be taken with the gauze-net or in the following way:—Tie a piece of small worm on to the end of a cotton threadfastened to the end of a willow or hazel switch. Cast into the part of the pond where the newts are, and await results.
Live newts, fish, frog spawn, etc., may be obtained from Messrs Willson, Live Stock Providers, 37 New Oxford Street, London; Thomas Bolton, 25 Balsall Heath Road, Birmingham, and other dealers. Newts should be fed once a day on pieces of small worms.
CATERPILLARS.—Caterpillars and pupæ, if not obtainable in local woods, fields, and gardens, can be had from Messrs Watkins & Doncaster, 36 Strand, London, and others.
CADDIS LARVÆ.—Caddis worms are to be found in almost every stream, pond, and ditch. Most of them are vegetable feeders: therefore a plentiful supply of water weeds should be placed in their tank. Carnivorous caddis worms may be fed on small pieces of raw meat. (See Stickle-backs.)
STICKLE-BACKS.—Stickle-backs are common in canals and streams. They are easily caught with the net. They should be fed once a day on grated biscuit, and occasionally on raw meat. The meat should be chopped very fine, and then pressed through a piece of perforated zinc. Very little food suffices. If too much is put in, the residue should be removed by means of a glass tube, as described in Lesson IX., p. 56. If no green water plants are obtainable, the water should be changed at least every second day by means of a siphon. Once a month is quite often enough if sufficient green plants are kept in the tank and decaying matter carefully removed. Do not over-stock—few fishes and much water is the rule.
WATER PLANTS.—It is best to take the water plants which are found growing locally. The following are fairly common:—Elodea canadensis, water millfoil;Potamogeton(nitens,crispus, orfiliformis), “water soldier”;Vallisneria spiralis,Chara,Nitella, water star-wort and watercress. A good selection of excellent aquarium plants are advertised at a cheap rate by the Solway Fishery Co., Dumfries. Water plants, if not rooted in the tank, should be renewed occasionally.
LARVÆ CAGE.—Take four square pieces (about 1½ inches square) of wood, each a foot long, and nail or screw them upright into the four corners of a square piece of ¾-inch deal measuring a foot each way. Stretch mosquito netting over sides, end, and top, arranging that one side can be opened. This can be managed by fastening the last fold of netting to one of the upright posts by three drawing-pins. Fresh leaves should be supplied daily. For those caterpillars which pupate in the soil, a shallow earthenware flower-pot—known in the trade as a “seed-pan”—should be supplied. The seed-pan should be filled with soil, the pupæ placed on the surface, and a layer of moss placed over them. Once a week the moss should be dipped in water, squeezed almost dry, and replaced on the pupæ.
AQUARIUM.—Procure from a local florist or seedsman what is known as a “propagating bell.” These cost from 1s. up to 2s. 6d. A block of wood 12 inches square and 4 or 5 inches in thickness is also required. Bore a hole about 2 inches in diameter right through the centre of the block, to hold the knob of the bell. Then, with a gouge chisel, make a saucer-shaped hollow round the hole, to roughly fit the rounded end of the bell. Before fitting the bell into the block, interpose a thin layer of moss.
This makes an excellent aquarium—elegant and serviceable. Keep the aquarium in a window, but shade it from bright sunlight.