XII.—HOW INSECTS GROW.
Those of you who have kept silkworms or other caterpillars must have noticed that these insects, from time to time, become listless, cease feeding, and finally 'moult,' or change their skin; but it may not have occurred to you to inquire why this change is necessary.
The reason is certainly a curious one, since it is the caterpillar way of growing. With most living creatures, growth is continuous until the full-grown size is reached; that is to say, it takes place by imperceptible degrees. Boys and girls add to the number of their inches so gradually that neither they themselves nor their friends can perceive the change, except by reference to old measurements. You cannot see people or animals growing, because the process is so steady and gradual. But with the insects, and their relatives, the crabs and lobsters, this is otherwise. Owing to its peculiar nature, the hard outer skin, which is of horny, or, as it is called, 'chitinous' nature, cannot grow gradually, and so the skin has to be cast off periodically. This casting-off process is known as 'moulting.' At each change of skin a sudden and easily noticed increase of size takes place; and, before further growth is possible, another moult must be undergone.
Directly after each moult the body will be found to be quite soft, but the skin quickly hardens again.
The manner in which the 'old clo'' are cast off is curious. For some time before the change takes place, the insect appears to 'sicken,' taking no food and wearing a very mournful air. At last it wakes up into something like activity. Now is the time to watch. If—in the case of a silkworm, for example—the watching is begun a little earlier than this, it will be found that the day before the change, the insect deliberately binds its hinder legs to the leaf on which it rests by silken threads. This done, it remains motionless. Soon after, through the transparent skin, a second head, larger than the first, will be seen; then the body is raised, and the skin is separated from it by the formation of a fluid which circulates between the old skin and the body. Next, by a series of vigorous movements, the old skin cracks along the back, and the insect first pushes out its head and the fore-part of the body, and then withdraws the hinder part. In a few minutes all is over, and the old skin is left bound to the leaf by the silken threads. How complete this change is may be seen from the fact that even the breathing tubes and the inner lining of the digestive organs are cast off.
This process, in the case of the caterpillar, takes place no less than four times—in some caterpillars five times. Ten days separate each of the first four moults, and an interval of sixteen days elapses between the fourth, or fifth, and last. This last moult is followed by a still greater change, the caterpillar passing into a state of coma, or sleep, during which it is turned into the butterfly or moth. For this purpose it spins a winding-sheet of silk, or digs down into the ground and forms a case, or cocoon; or else it hangs itself by the tail, and becomes strangely transformed into what we call a 'chrysalis.' From the cocoon, or chrysalis, as the case may be, the butterfly or moth sooner or later makes its appearance.
Fig. 1.—Dragon-fly moulting.
To give an idea of the great increase of growth in insects, let us take the case of the silkworm. At the time of hatching, the little worm weighs about the one-hundredth part of a grain; when fully grown, it weighs ninety-five grains. During this time, therefore, it has increased ninety-five thousand times its original weight, and it has eaten sixty thousand times its weight of food!
Fig. 3.—Empty Case of a Newly-moulted Cockroach.
The change from the worm-like caterpillar to the butterfly is a great one, and, if we did not know it so well, would be startling. This change is known as a 'complete metamorphosis.' The dragon-fly is another insect with a complete metamorphosis. How the dragon-fly moults you will see in the illustration (fig. [1]): even an acrobat might envy him!
Carefully examine the series of figures from a to d. The empty case at a shows the last stage of the larval life. Out of this case the young dragon-fly is just emerging. In c he has gained his freedom, and is stopping to take breath and allow his wings to expand. By the time this has taken place, they will be nearly as long as the body (as in d).
The locust furnishes us with an instance of what is known as 'incomplete metamorphosis.' In other words, the young, when they emerge from the egg, are very little different from the parent form. The youngest locust in the illustration (fig. [2]) is obviously a locust, though he lacks wings; but there is no promise of the butterfly in the worm-like caterpillar.
Fig. 2.—Stages of Locust's Growth.
The cockroach, like the grasshopper and the locust, only undergoes an incomplete metamorphosis. The empty case of a newly-moulted cockroach is shown in fig. [3]. The slit(s) along the back marks the spot where the insect crept out.
TOYS FROM THE STREETS.
Some More Toys from the Streets.
The most remarkable toy in our second illustration is that in the middle. It is a wonderful Japanese screen or fan, which shuts up into the space of a few inches. These fans are made in three sizes, the largest, and the very latest, as far as invention goes, being eighteen inches in diameter. The whole of the fan is made by machinery! An amazing machine cuts out each layer of paper of the proper size and shape, and when all the parts are ready, sticks them neatly together. Most Japanese toys—which really are Japanese, not mere imitations of Japanese designs—are made by hand; but this one is due to machinery alone.
The other toys in this picture are mostly machine-made, and their uses can be easily seen. But the cup and ball, and the 'two bears,' as the strange figures hammering on an anvil in the top left-hand corner are called, are made by hand. The latter comes all the way from a little village in Austria, and the figures are cut out by the villagers in their homes, before being fastened together. The sewing-machine is one of the most popular toys: thousands of gross of these have been sold, according to Messrs. Lawrence, of Houndsditch, who very kindly gave us some facts about this business. A 'gross' means one hundred and forty-four; when you consider that many times one hundred and forty-four thousand have been made and purchased, you will see what a vast trade is done.
The little train in a box, a very popular toy, is made in Germany, mainly by machinery. All the wheels of each carriage go round, and the carriages themselves can be unhooked and used separately. The funny little camera—of course, it does not take real photographs—is an English toy. So is the tiny tin of biscuits. The biscuits are real, and are made specially for these wonderful little boxes.
THE LOVER-DOLL.
ardon, dearest Araminta,
If I go not on my knees,
For my joints are out of order,
When I bend they crack and wheeze.
When I saw you in the doll's-house,
Then I felt young Cupid's dart
Striking through my crimson waistcoat,
Till it stuck within my heart.
Though my blood is not the bluest,
Still, for you (the fact remains)
I would gladly shed the last drop
Of the sawdust in my veins.
Do not scorn me, Araminta,
To my suit your favour lend;
I would fold my arms around you,
Only that I cannot bend.
For, before I fell in love, dear,
Ere I hoped with you to wed,
Careless Mistress Baby dropped me
Down the stairs upon my head.
But I'll probably recover
When I've had a dose of glue,
And, come life or death, will ever
Be to Araminta true.
HIS FIRST WOLF HUNT.
By Harold Ericson.
It happened in Russia, when I was spending the winter with a cousin who lives in St. Petersburg. This was ten years ago and we were mere boys, both of us. There is plenty to do in Russia, in winter, for those who like sledging, skating, ice-yachting, and so on, and I think I thoroughly enjoyed all these forms of amusement. Well, one day near the beginning of the winter, before the really great snows had fallen, a big wind came and swept away every particle of snow that had fallen from the twenty miles of ice which divided St. Petersburg from Cronstadt, thus giving us such an opportunity for a day's skating on a grand scale as we might never meet with again throughout our lives.
My cousin Tom had an idea in the evening just before bed-time, with the result that we ordered sandwiches for an early hour next morning and went to bed promptly, our minds full of the delightful day we were going to spend on the Gulf of Finland, now a shining field of splendid, smooth ice.
The great day broke magnificently, a glorious, sunshiny December day, the thermometer at zero, or near it, but the air so dry and bathed in sun that one was not conscious of the cold.
Oh, the joy of feeling oneself flying through the air as we raced side by side over the firm, glass-like plain of ice! We must have skated at full pace for five miles at least before we pulled up, puffing and gloriously happy, in response to an exclamation from Tom.
'It's splendid,' he said, 'and I should like to go on for miles and miles; but Father warned me to look out when we came somewhere near the middle of the gulf; he has skated here a good deal in former years, and he says one must be on the look-out for fissures which are caused by a very hard frost like this; the ice suddenly cracks and parts, sometimes only a few inches, sometimes several feet, even up to fifteen feet or so. I believe I see a crack on ahead, and that's why I stopped.'
We skated slowly forward a short way. Sure enough, there opened out before our eyes, plain as possible, a fissure of several feet in width, the water looking black and cruel as it welled up to the edge of the ice as though it longed to get at us.
'Nice sort of place if one had skated up to it at dusk, eh?' said Tom.
The water certainly looked very grim.
'It's all very well, but what are we going to do?' said I. 'It will be no fun if this is the end of our skate, and we can't get to Cronstadt!'
'Perhaps it's only a local crack; we will skate along it, first one way and then the other, and see.'
We did so, but it appeared that the spot at which we originally struck the fissure was the narrowest place; it widened at either side.
We stood and stared at it. Tom spoke first.
'Dare you?' he asked.
I saw what he meant and remained silent, considering. 'It's about six feet,' I said, 'I suppose one could fly it—both feet together, eh?'
'Yes; come on—no use thinking—we will go for it; I will give you a lead. Hold out your coat to me and pull me in if I fall short.'
Tom took a good run, got up a great speed, and launched himself into the air. He must have cleared eight or ten feet at least. 'Come on!' he laughed, 'it's as easy as winking.'
I must confess that I was more than a little frightened as I prepared to follow my daring cousin. I imitated his methods as closely as I could; I got a terrific speed up and let myself go.
I cleared the open water easily, but so great was my impetus that I turned head over heels at the other side, and lay panting and laughing on the ice.
Presently we were in full sweep once more towards Cronstadt; we reached the 'half-way house' without adventure; this was a little wooden hut built on the ice for the accommodation of travellers in need of shelter or warmth. It was kept by a man and his wife, who must have found it a weird house to live in all the winter.
'We heard wolves last night,' they told us; 'get back before dusk if you are wise!'
We thought little of the warning. We meant to be home by daylight. As for the wolves, they would have to be active animals to keep up with us at our pace!
Having enjoyed a cup of coffee and a cake apiece we continued our journey, and a few miles beyond the rest-house, came across another fissure which we calculated to be ten feet across.
By this time we were reckless, or very over confident. 'My turn to give you a lead!' said I, and suiting the action to the words, I worked up pace, flew out, and cleared the black water with ease. Tom followed and cleared it also, but in alighting he twisted his ankle a little. He uttered an exclamation of pain and sat down a moment, rubbing his leg. He said it was nothing serious, however, and indeed, he was up and off again in a few moments.
AN IMPRESSION OF ZANZIBAR.
A curious sight is told of by a gentleman who was lately in Zanzibar. 'Perhaps the most vivid impression that I brought away from my hurried visit to Zanzibar,' he says, 'was that of seeing the native carpenters in the Cathedral carving the memorial to Bishop Smythies, and planing with their toes, which were decked with silver rings!'