Something About Spiders
( Originally Published Ealry 1900's )
THE Spinners are neighbors of ours. They set up their housekeeping in our yards and gardens, in our barns and cellars, and sometimes in the best rooms of our houses. They are skilful little architects and builders, but they are so quiet and even wary about their work that few people ever succeed in catching them at it.
We must visit them in their homes to find out what they do and how they do it.
Here is Mrs. Epè-i-ra Vulgaris, who lives in the garden. She is often called the garden spider, but I sup-pose she has no more right to the name than a dozen other Spinners who live in the same place. She builds her house in open spaces among the vines of the grape arbor, or the branches of trees ; sometimes she swings it far above your head among the leaves of the woodbine which cover the back porch.
She is a shy little body, and cares nothing whatever about making your acquaintance. Indeed, she prefers to keep out of your sight, so she tucks herself away in her private chamber and stays there all day long, coming out to her living-room among the vines only after sunset. But even the twilight shows us that she is a very pretty little lady,, dressed in a dainy pink gown with brown and white trimmings.
Like all the rest of the Spinner family, Mrs. Epeira has but two distinct divisions to her body. The foremost part is the head and chest combined. If we wish to be very exact, we must call this the cephalo-thorax. The hinder portion is the abdomen. This is almost five times as large as the cephalo-thorax.
Small as the front division is, all of Mrs. Epeira's legs are attached to it, and that means no small thing, for she has no less than four pairs. No wonder she can glide down her rope ladder so fearlessly when she has eight feet and legs with which to hold on!
Every leg is made up of seven pieces or segments. The first round segment, called the coxa, attaches the leg by means of a firm membrane to the under side of the body. The coxas of the eight legs form an oval surrounding the sternum or breast of Mrs. Epeira.
Next to the coxa comes another small, roundish segment, then a long, strong one, the femur. The next two segments look as if they really belonged together as one, with a bias seam across the middle. The last, pointed segment is the foot, or tarsus.
But really we must have a peep at this many-jointed leg under the microscope before we can see all of the interesting things that it has to show us. There it is, clothed from coxa to toe with hairs, all extending down-ward toward the foot. Some of them are fine and soft as silk, while others are stiff and bristling like small dark thorns.
At the end of the foot you see three hooked claws, as sharp as those of your eat. Besides these, there are a number of small ones so fine and sharp that they make you think of a bunch of tiny needles. These are called spines. Surrounding both claws and spines is a covering of long, stiff hairs.
You are wondering what Mrs. Epeira does with her eight feet and legs and her twenty-four sharp claws. In the first place she rims very rapidly; with four pairs of legs to carry her I suppose she ought to run four times as fast as you do with one pair. Then she performs all sorts of athletic feats that she never could do if it were not for her numerous hooked claws. These help her to climb up a vertical wall, or to run along one of her tight-rope walks, without any fear of tumbling off.
Then, too, she never could cling as she does to the filmy lace hub of her house if it were not for these dainty hooks. And above all, she never could build her wonderful house of silk without the aid of these same tools, which serve so many purposes.
She uses her feet to help to hold her food up to her mouth while she eats her dinner, for you know she has no fingers with which to hold it.
Her first pair of legs serve as feelers, just as the antennæ of a grasshopper or a butterfly do. She waves them about to discover whether or not any danger lies in her way.
How would you like to carry a clothes-brush around with you every minute? That is what Mrs. Epeira does. She is a very neat little lady, and if you watch care-fully you will see her brushing the dust from her pink gown, and even from her face and eyes, with the soft brushes of hair that she carries on her legs.
There are some other ways in which these interesting feet and legs are made to serve their owner. You notice that they are pretty long for such a small body. When you visit the Lady Spinner in her home you will see that the length of the legs makes it easy for her to spread out her weight over a large space, so she runs no risk of breaking down the delicate walls of her house.
Then, too, there are times when Mrs. Epeira must walk with part of her legs, hold the thread that she cuts with another part, and help to weave with another, all at the same time. So you see she finds enough to do to keep even eight feet and legs busy.
As we look again at Mrs. Epeira she seems to have another pair of legs, a short pair in front of all the others. Have we made a mistake after all, Mrs. Epeira, and have you ten legs instead of eight?
She only wriggles around and shakes her house a little, as much as to say, " Find out for yourself if you can, for I will not tell you."
That is just what we expect to do, Mrs. Spinner. If those short appendages are not legs, we shall find out what they are and what they are good for.
There, she has skipped across the entire length of her dining-room, and I am sure she does not use them to run with. Now she has caught a dusty. little miller for her supper. Oh, Mrs. Epeira, your secret is out! You are using those foot-like projections to hold the little insect close to your mouth while you eat it.
So these appendages are not feet, but belong to Mrs. Epeira's mouth parts and are called palps, or feelers.
This Lady Spinner's mouth is very, very different from yours. Instead of having teeth and tongue on the, inside, as you have, her teeth, and tongue too, are out-side of her mouth, so all of her food must be chewed be-fore it goes inside. This being true, she could never get along without her palps to hold the food in just the right place while she is chewing it.
Each palp is made up of six segments instead of seven — the number, you remember, which we found in the legs. Instead of three claws at the end, there is but one. The segment nearest the body is flat and strong. It is toothed on its inner margin like a saw. This segment and its mate on the other palp form a pair of small jaws called maxillae. These jaws move back and forth like a pair of scissors, crushing the food.
You would think that one pair of jaws was enough for Mrs. Epeira, but it is not. She has another pair, much larger and stronger than the maxillae. These are the mandibles, or true jaws. Look her straight in the face, and you see the mandibles, like a pair of cylinders, fastened to the front of her head. These are furnished on the inner margins with the same kind of saw-teeth that you saw on the maxillae.
But this is not all. At the tip of each mandible, Mrs. Epeira carries her weapons. For you must know that all the Spinners make their living in the old-fashioned way, by hunting or trapping. That being the case, they must carry about with them some sort of weapons with which to kill their prey. The weapons are strong spears, sharp enough to pierce through the skin of any insect the Spinner may capture.
I am afraid you will think Mrs. Epeira is a dreadful little savage, for she poisons her spear before she strikes with it. At the tip of each spear is a tiny opening, so small that you cannot see it without the aid of a micro-scope, and yet it is large enough to allow a jet of poisonous liquid to pass into the wound made by the sharp point. In this way the immediate death of the prey is insured. The liquid is secreted in a small bag, or gland, which is concealed in the upper part of the mandible. A tiny duct carries the liquid from the gland to the tip of the poison-fang.
Mrs. Epeira never uses her sharp weapons just for the fun of killing things. She uses them when she is hungry, to kill insects for her food, or to defend herself against the attack of an enemy.
If you were to catch her in your hands, she might try to punish you by piercing your finger with her poisonous weapon. And I am sure no one would blame her if she did. However, if that should happen, you need not be alarmed, for although the poison makes quick work of killing flies and other insects, it will have but little effect on you. It may make your finger smart or burn for a short time, in much the same way that the sting of a wasp or a bee would serve you.
But remember this, that in spite of all the bad stories you may have heard about Spinners trying to bite people, no Spinner will ever use her poison-fang on you if you do not first attack her and compel her to bite you in self-defence.
When Mrs. Epeira has captured her prey, she sets about chewing it up with all those pointed teeth on her mandibles and maxillae. She chews for hours at a time. There is good reason for this, for no Spinner ever eats any solid food; everything must be reduced to the liquid state before it is sucked into the mouth with the thin lips.
When you remember Mrs. Epeira's eight feet, her four jaws, and her numerous claws, you will not be surprised to learn that this extravagant little lady possesses no less than eight eyes.
Eight eyes ought to enable one to see very well in-deed, but the truth is that all Mrs. Epeira's eyes are not of so much service to her as your two are to you. They are so small that at first glance you are inclined to believe she has no eyes at all. A closer look reveals the dainty jewels set tastefully in the front part of her cephalo-thorax.
They are arranged two on the top of her head, two in front just above the mandibles, and two very close together at each outer corner of the cephalo-thorax.
It is a good thing for Mrs. Epeira that her eyes are scattered about so that she can see in every direction, for you know she can never turn her head around to see what is going on behind her.
These tiny eyes are of the kind called simple eyes. They cannot see long distances, as the wonderful compound eyes of the flies and other insects can. They are near-sighted; that is, they can see only those objects that are within a few inches, or at best a foot of Mrs. Epeira's body. They never give her the image of an entire object at one time. When you come near the little Spinner, she sees but a small portion of you, yet that is enough often to frighten her away. What would she do if she could see what a great giant you really are?
After all, eight eyes are not too many when they are very small, simple ones.
But Mrs. Epeira and all her kindred have other ways of finding out things in the world. They can hear as well as see. Just how they manage to hear without ears is not so easy to understand. However, those who have made a careful study of the Spinners believe that some of the fine hairs on the palps act as hearing organs. Other hairs serve as the organs of smell.
Although Mrs. Epeira can see, and hear, and smell, she does not depend on any of these senses half so much as she does on her sense of touch. Most of the hairs on het legs, and those scattered over her body, are sensitive hairs, so sensitive that she knows instantly the moment you touch any part of her silken house.
It is this wonderful sense that tells her not only that an insect has entered her home, but the exact spot where it is to be found.
Indeed, Mrs. Epeira's sense of touch is as good as a hundred eyes, for it enables her to work just as well in the darkness as in the light. And that means a great deal to her, for she does almost all her building under cover of the night.
The appendages we have found thus far, legs and palps, jaws and eyes, have all been fastened to Mrs. Epeira's cephalo-thorax. But attached to her abdomen is the most wonderful of all this little Spinner's possessions, that is, her spinning-machine.
The abdomen itself is large and round, and is fastened to the cephalo-thorax by a small stalk. On its upper surface are a number of queer little markings that look as if some one had tacked the skin fast to something on the inside. And really that is about what has happened, for these dents are the spots where the ends of the muscles on the inside are fastened to the walls of the body.
The spinning-machine is found near the end of the abdomen on the under side. It is composed of six blunt projections that resemble finger-tips. These are called spinnerets, or sometimes spinners. Every spinneret is pierced at the end with hundreds of tiny, tube-like openings. It is through these tubes that the delicate silk for Mrs. Epeira's weaving is drawn out.
On the inside of the abdomen, just above the spinnerets, is a bunch of little pouches or sacs. From each pouch a small duct leads to one of the tube-like openings on the spinnerets. These pouches are glands that secrete a clear, watery liquid. This means that a portion of the food eaten by Mrs. Epeira is digested or changed into a peculiar fluid which is stored away in these tiny pouches.
When this little lady is in need of some silk, she gently presses her spinnerets against an object and forces a small amount of the fluid through the tube openings. This adheres to the object and then she moves her spinnerets in just the right way to draw the liquid from the tubes. The instant the liquid meets the air it is hardened into a thread.
If you have ever examined an ordinary sewing-thread you know that it is made up of a great many small strands twisted together. That is why it is so strong. Mrs. Epeira knows well enough that one of the delicate threads drawn from a single tube is too slight to be of any use to her, so she dexterously holds the fingers of her spinning machine close together, and in just the right position, so that the hundreds of dainty strands are united into one firm thread, strong enough to support Mrs. Epeira's own body.
A strange thing about the spinnerets is that they do not all contain the same kind of silk; therefore Mrs. Spinner rarely uses them all at the same time. When she wishes to use one sort of silk she spins with one set of the finger-tips. When she decides that she needs another kind she skilfully changes to another set, and goes on with her work with scarcely a pause. She never makes a mistake, never uses the wrong kind, and never mixes up the different sorts.
Years and years ago, your grandmother and great-grandmother stood by their spinning-wheels and spun woolen and cotton threads. As they spun they deftly drew out with their hands the long threads, so there would be no danger of breaking or tangling. Now Mrs. Epeira has no hands with which to draw out her threads, but she has something just as good. The claws on her feet take the place of fingers. With these dainty tools she ingeniously guides her thread, carrying it out to one side, keeping it from adhering to surrounding objects, and fastening it where she wishes it to be. Sometimes she uses her claws to draw the threads from the spinnerets.
Now and then the skilful little Spinner wishes to use a band of silk instead of a strong thread. When that is the case she holds her spinnerets apart so that the hundreds of threads unite side by side instead of twisting together, and the band is made.