CHAPTER XXXIV

SPIDERS AND SCORPIONS

Most people think that spiders are insects. But this is a very great mistake, for they are just about as unlike insects as they can possibly be.

Insects, for example, always have distinct heads. But spiders never do, for their heads are so sunk and lost in their chests that you cannot possibly tell where the one leaves off and the other begins. So that spiders have their bodies divided into two parts only instead of into three, as is always the case in the insects.

Then insects always have six legs; spiders always have eight. Insects have wings; spiders have none. Insects have feelers; spiders have none. Insects nearly always have a great many eyes, which are six-sided; spiders never have more than eight eyes, which are round. And while insects may have biting jaws, or sucking jaws, or a trunk, or a beak, spiders always have poison-fangs, which no insect ever possesses.

So you see that as far as the outside of their bodies is concerned, spiders are very different indeed from insects. And the differences inside the body are just as great. Insects have no hearts, the only blood-vessel in their bodies being one long tube which runs along the back; but spiders have quite a big heart, and a good many arteries as well. Insects have no lungs, but breathe by means of slender tubes which run to every part of the body; but spiders have quite big lungs, in which the blood is purified just as it is in our own. Insects have no brains, but only bunches of nerves in different parts of their bodies; but spiders have quite big brains. And besides this, while all insects which spin silk produce it through their mouths, spiders always do so by means of organs at the very end of the body. So that inside, as well as outside, there is hardly any respect in which spiders and insects really resemble one another.

The silk-organs of a spider are very wonderful indeed. Remember, in the first place, that the silk, as long as it remains in the body of the spider, is a liquid--a kind of thick gum, which is produced and stored up in six long narrow bags, or glands. Then if you look at the end of a spider's body through a good strong magnifying-glass--or, better still, through a microscope--you will see several little projections, which we call spinnerets. Now each of these spinnerets is covered with hundreds of tinier projections still, every one of which has an extremely small hole in the middle. And all these holes communicate, by means of very slender tubes, with one of the silk-glands.

So what a spider does when it wants to spin its line is to squeeze a little drop of silk into one of the spinnerets. It then just touches the object to which the line is to be fastened, and draws its body away. And as it does so a delicate thread comes out from every one of the projections on the spinneret; and all these threads unite together into one stout cord. That is why a spider's thread is so strong. It really consists of several hundred separate threads all firmly fastened together. And if the spider wants to spin a stronger line still, it can unite all the threads coming from several spinnerets into one, so as to make a very stout cord indeed.

Spiders use this silk for all sorts of different purposes. In the first place, they use it for snaring insects.

THE GARDEN-SPIDER

Let us take for an example, the web of the common garden-spider. It is to be seen in every garden, resting in the middle of its web; and you may always recognize it by the white cross upon its back. But I don't suppose that you have ever seen it spinning its net. For it always does so very early in the morning, generally beginning before sunrise, so that it may be quite ready for use as soon as the insects begin to fly.

First of all, the spider makes a kind of outer framework of very strong silken cords, and fastens it firmly in position by stout guy-ropes of the same material. Next, she carries a thread right across the middle and fixes it down on either side. Then, starting from the center, she carries thread after thread to the margin, carefully testing the strength of each by giving it two or three smart pulls, and fastening it firmly down. When she has finished this part of her task, the web looks like a badly shaped wheel.

The next thing that the spider does is to spin a little silken platform in the middle of her web to sit upon. And as soon as she has done this she begins to spin the spiral thread. Beginning from the center, she goes round and round and round, fastening the thread down every time that it crosses one of the straight cords--the spokes, as it were, of the wheel--until at last the web is finished. Then she goes to the little platform in the middle, and there remains, upside down, waiting for an insect to blunder into her net.

By and by, perhaps, a bluebottle fly does so. Then she shakes the web violently for a few moments, so as to entangle it more thoroughly, rushes down upon it, seizes it, and plunges her fangs into its body. But if she catches a wasp or a bee she nearly always cuts it carefully out, drops it to the ground, and then patches up the hole in her web. For she knows perfectly well that wasps and bees can sting!

Would you like to know why it is that flies stick to the web as soon as they touch it? The microscope shows us. All the way along, the spiral thread is set with very tiny drops of liquid gum. So tiny are these drops indeed, that there are between eighty and ninety thousand of them in a large web! And would you like to know why it is that the spider does not stick to the web as the flies do? Well, the fact is that only the spiral thread is set with these little gummy drops, and that as the spider runs about over her web she is most careful to place her feet only on the straight threads, and never on the spiral line. Other spiders, however, snare their prey in quite a different way.

THE MARMIGNATTO

This small spider, found on our western plains, is remarkable for feeding on large insects, such as grasshoppers and field-crickets, which it catches in an ingenious manner. It stretches a few silken threads across a narrow path way, quite close to the ground, along which these insects are likely to pass, and lies in wait just opposite until a grasshopper or a cricket approaches. When it comes to the threads the insect is sure to get at least one of its feet entangled. Then it stops, and tries to shake itself free. The only result of its struggles, of course, is that its other feet become entangled too; and while it is struggling the marmignatto springs upon its back, fastens a silken thread to it, springs down again, and fastens the other end to a grass-stem close by. Over and over again it does this, and before very long the unfortunate insect is firmly fastened down by hundreds of threads, and is quite unable to break free, or even to move one of its legs. Then the spider leaps upon its back once more, plunges its fangs into its body, and proceeds to suck its blood.

HUNTING-SPIDERS

Perhaps you may have seen little hairy black spiders, with white markings upon the upper part of their bodies, running about in an odd jerky way on sunny fences and walls. These are called hunting-spiders, because they hunt their prey instead of snaring it. You may see them gradually creeping up to a fly, so slowly that they hardly seem to move, and then suddenly leaping upon it when they are about two inches away. Then spider and fly, locked in one another's embrace, go falling toward the ground together. But they never reach it, for wherever a hunting-spider goes it always trails a rope of silk behind it, and fastens it down at intervals. So when it springs from the fence it is brought up at once by its own thread, and swings in the air till its victim is dead. Then it just climbs up its thread, and so gets back to the fence.

BIRD-SPIDERS

These great spiders of the tropics hunt for prey in much the same way. Only instead of catching flies on walls they prowl about the branches of trees in search of small birds, springing upon them when they are roosting at night, and killing them almost immediately by a smart bite from their venomous fangs. These spiders, of course, are very large. Indeed, the body of a full-grown bird-spider is as big as a man's fist, while its great hairy legs cover nearly a square foot of ground when they are fully spread out.

TRAP-DOOR SPIDERS

These famous spiders are found more or less commonly in all warm countries. They all live in tunnels in the ground, which they dig by means of their fangs; and as they do not want the situation of their nest to be discovered, they carry the earth away to a little distance as fast as they dig it up, and carefully hide it. Very often the hole which they dig in this way is eighteen inches or two feet deep. And at the bottom it always turns sideways for an inch or two, so that the general shape of the burrow is very much like that of a stocking.

This hole is always dug in the side of a bank, so that when there is a heavy fall of rain the water may run away without flooding it.

When the burrow is finished, the spider lines it throughout with two sheets of silk. The outer sheet, which comes next to the earth, is rather coarse in texture, and is quite waterproof, in order to keep the tunnel dry. The inner one is very much finer and softer, so that the little home may be as comfortable as possible.

As soon as the lining process is completed, the spider sets to work on the trap-door. This she makes in the cleverest manner possible. First she measures the doorway most carefully by the aid of her feelers. Then she spins a thin silken pad of exactly the same size and shape. This is sticky on the top, like the spiral thread of the web of the garden-spider: and she sprinkles it all over with very small scraps of earth. Upon this she fastens another silken pad, which she sprinkles with earth in the same way. And then comes another and then another, and so on till the door is sufficiently thick. Finally, she fastens it in position by means of a hinge, which is also made of silk; and she always places this hinge on the upper side of the doorway, so that the door may fall down behind her by its own weight whenever she leaves the burrow. She is rather a lazy creature, you see, and does not want to have the trouble of shutting the door for herself! And if she left it open, every passer-by would find out where she had made her home.

The door always fits most wonderfully into its place, and the spider carefully covers the top with little bits of moss and small scraps of earth and stone, so as to make it exactly like the surface of the ground all round it. Indeed, unless one happens to see the spider push it open, it is almost impossible to find it.

When one of these spiders is in her burrow, she always fastens about half a dozen silken threads to the inner side of the door, carries them down to the bottom, and sits with one of her feet resting upon each. No one can then try to force her door open without her knowledge, and as soon as she feels the least pull upon the threads she rushes up the burrow, clings to the walls with her hind feet, seizes the door with her front ones, and pulls it downward with all her might. And if the door is forced open in spite of her efforts, she slips into a sort of side tunnel which she always makes near the top of her burrow, and stays there until the danger is past.

THE RAFT-SPIDER

There are several spiders which live on or in the water. One of these is the raft-spider, which is found in the fen districts of England. If you should happen to meet with it you can recognize it at once, for all round the upper part of its body is a narrow band of yellow, and inside this is a row of small white spots.

This spider is about an inch long, and owes its name to the fact that it actually makes a little raft on which to go out searching for water-insects. Collecting together a quantity of little bits of leaf and cut grass and reeds, it fastens them firmly together with silken threads, just as shipwrecked sailors might lash planks together with ropes in order to escape from a sinking vessel. In this way it makes a small floating platform, perhaps a couple of inches in diameter. When the raft is finished, the spider gets upon it, pushes off from the shore, and allows the current to carry it along. By and by, perhaps, it catches sight of some water-insect floating at the surface, or of a drowning fly which has fallen into the stream. Then it leaves its raft, runs along over the surface of the water, seizes its victim, and carries it back to the raft to be devoured. And if it should be alarmed, or think itself in danger, it gets under the raft and clings to the lower surface, so that it cannot be seen from above.

THE WATER-SPIDER

More curious still is the water-spider, which actually makes its nest under water. This spider, which is almost black in color, and has a very hairy body and legs, is common in ponds and canals, and spends almost the whole of its life beneath the water. Its little silken nest is shaped like a thimble, with the mouth downward, and is placed among weeds, to which it is firmly fastened down by guy-ropes, also of silk. And when it is finished the spider fills it with air. She does this in a most curious manner. Rising to the surface, she turns upside down, pokes her long hind legs out of the water, and crosses the tips. Then she dives again, carrying down a big bubble of air between these hairy legs and her equally hairy body as she does so. She next gets exactly underneath the entrance to her nest and separates her legs. The result is, of course, that the air-bubble floats up and occupies the upper part. Another bubble is now brought down in the same way, and so the spider goes on, fetching bubble after bubble, until at last her little nest is completely filled with air. Then she gets inside it, and watches for the grubs of water-insects to swim by.

In this wonderful nest the spider lays her eggs and brings up her family. When the little ones have been hatched, of course, the air in the nest very soon becomes too impure to breathe. Then the little spiders cling tightly to the walls, while the mother gets outside and tilts the whole nest sideways, so that all the exhausted air floats up in one big bubble to the surface. Then she pulls the nest back into position, hurries up to the top of the water and brings down a bubble of air, and then another, and so on until the nest is filled with air all over again.

If you ever catch one of these spiders, and keep it for awhile in a jar of water with a little piece of water-weed, you may see it spinning its wonderful nest, and filling it with air, perhaps half a dozen times a day.

GOSSAMERS

Before we leave the spiders altogether, we must tell you something about the wonderful little creatures called gossamers. These are really the young of a good many different kinds of spiders. It often happens, of course, that several families, with perhaps five or six hundred little ones in each, are all living quite close to one another. The result is that there is not sufficient food for them all. So they make up their minds to go out into the world and seek their fortunes; and this is how they do it.

Choosing a warm, sunny morning in the early part of the autumn, all the little spiders climb the nearest bush, and each one makes its way to the very tip of a leaf. Then, clinging firmly to its hold, it begins to pour out a very slender thread of silk from one of its spinnerets. You know that on warm, sunny days the air near the ground soon becomes heated and rises, as hot air always does; and in rising it carries up these delicate gossamer-threads, as they are called, with it. Still the little spiders hold on, and pour out their lines, till at last each has several feet of thread rising straight up into the air above it. Then suddenly they all let go, and are carried up into the air at the ends of their own threads. So they go on, up and up and up, till at last they meet a gentle breeze, which carries them along with it. So, perhaps, they travel for thirty, forty, or fifty miles, or even farther still. And when at last they make up their minds to descend, all that they have to do is to roll up the threads which have been supporting them, and down they come floating gently back to earth. One good name for them is ballooning spiders.

Haven't you sometimes found on a warm autumn morning that all the trees and bushes, and even the grass and low plants, are quite covered with threads of silk? The next time you see such a sight look carefully, and you will find that on every thread a little baby spider is sitting. Then you may be quite sure that all these little spiders set out early in the morning to seek their fortunes, and that, borne up by their slender threads, they have traveled for many long miles through the air.

SCORPIONS

These formidable creatures are closely related to the spiders. They are found in all warm countries, with the exception of New Zealand, and may easily be known by two facts. In the first place, in front of the legs they have a pair of great, strong claws, which look very much like those of a crab. And in the second place, the last five joints of the body are narrowed into a long, slender tail, at the end of which is a claw-like sting. When they attack an enemy, or seize a victim, they grasp it with the claws, turn the tail over the back, and force the sting into its body. And the poison which is introduced into the wound is so powerful that the sting of a large scorpion is almost as severe as the bite of an adder.

During the daytime scorpions hide away under stones and logs, or in crevices in the ground, or perhaps under the loose bark of dead trees. But very soon after sunset they come out from their retreats and prowl about all night long in search of insects; and it is at such times that they invade camps and houses, get into shoes, etc., and persons get stung unless they are very careful.

CENTIPEDES AND MILLEPEDES

One can easily recognize centipedes by the great number of their feet. The name centipede, indeed, means hundred-footed. None of these creatures, however, have exactly a hundred limbs. Some only have fifteen pairs of legs; some have as many as one hundred and twenty-one pairs. But whether they be many or few, the number of pairs is always odd.

Another very curious fact about centipedes is that they have no less than four pairs of jaws. But the fourth pair take the form of fangs, which are very stout and strong, and very much curved, while at their base, just inside the head, is a little bag of poison. In the northern centipedes, which are quite small, the fangs are not large enough, nor the poison sufficiently strong, to cause a serious wound. But some of the tropical species, which grow to the length of nearly a foot, are quite as venomous as the largest scorpions.

The food of these creatures consists chiefly of worms and insects. But the larger ones will kill lizards, and even mice, and have been known to prey upon victims actually larger than themselves.

The eggs of centipedes are laid in little clusters on the ground in some dark, damp nook, and when they have all been deposited the mother centipede coils herself round them, and there remains guarding them until they hatch.

Millepedes, in some ways, are very much like centipedes; but they only have two pairs of jaws instead of four, and they are nearly all vegetable-feeders. The long, smooth, and slender _Julus_ millepedes are plentiful in every garden. And in tropical countries they sometimes grow to a length of six inches. Even the largest, however, are perfectly harmless, for they have no poison-fangs as the centipedes have, and the only way in which they ever attempt to defend themselves is by pouring out a small drop or two of a fluid which smells rather nasty, and no doubt protects them from the attacks of birds.