Chapter XXX: Part II: Animal Life (23)

6. Look closely at the head. Can you see the hooked jaws, or fangs? Can you see the palpi on each side of the jaws? Where are the spider’s eyes? How many pairs has it?

* * * * *

_When the tangled cobweb pulls
The cornflower’s cap awry,
And the lilies tall lean over the wall
To bow to the butterfly
It is July._
--SUSAN HARTLEY SWETT.

Photo by J. H. Comstock.

_A funnel web._]

THE FUNNEL WEB

_Teacher’s Story_

“_And dew-bright webs festoon the grass
In roadside fields at morning._”
--ELIZABETH AKERS.

Sometimes on a dewy morning, a field will seem carpeted with these webs, each with its opening stretched wide, and each with its narrow hallway of retreat. The general shape of the web is like that of a broad funnel with a tube leading down at one side. This tube is used as a hiding place for the spider, which thus escapes the eyes of its enemies, and also keeps out of sight of any insects that might be frightened at seeing it, and so avoid the web. But the tube is no cul-de-sac; quite to the contrary, it has a rear exit, through which the spider, if frightened, escapes from attack.

The web is formed of many lines of silk crossing each other irregularly, forming a firm sheet. This sheet is held in place by many guy-lines, which fasten it to surrounding objects. If the web is touched lightly, the spider rushes forth from its lair to seize its prey; but if the web be jarred roughly, the spider speeds out through its back door and can be found only with difficulty. The smaller insects of the field, such as flies and bugs, are the chief food of this spider; it rarely attempts to seize a grown grasshopper.

The funnel-shaped webs in dark corners of cellars are made by a species which is closely related to the grass spider and has the same general habits, but which builds in these locations instead of in the grass.

LESSON CXI

THE FUNNEL WEB

_Leading thought_--The grass spider spins funnel-shaped webs in the grass to entrap the insects of the field. This web has a back door.

_Method_--Ask the pupils to observe a web on the grass with a spider within it.

_Observations_--1. What is the general shape of the web? Is there a tunnel leading down from it? Why is it called a funnel web?

2. Of what use is the funnel tube, and what is its shape? Where does it lead, and of what use is it to the spider? Can you corner a spider in its funnel tube? Why not?

3. How is the web made? Is there any regularity in the position of the threads that make it? How is it stayed in place?

4. Touch the web lightly, and note how the spider acts? Jar the web roughly, and what does the spider do?

5. What insects become entangled in this web?

6. Compare this web with similar funnel webs found in corners of cellars, sheds or piazzas, and see if you think the same kind of spider made both.

THE ORB-WEB

_Teacher’s Story_

Of all the structures made by the lower creatures, the orb-web of the spider is, beyond question, the most intricate and beautiful in design, and the most exquisite in workmanship. The watching of the construction of one of these webs is an experience that brings us close to those mysteries which seem to be as fundamental as they are inexplicable in the plan of the universe. It is akin to watching the growth of a crystal, or the stars wheeling across the heavens in their appointed courses.

The orb-web of the large, black and yellow garden spider is, perhaps, the best subject for this study, although many of the smaller orbs are far more delicate in structure. These orb-webs are most often placed vertically, since they are thus more likely to be in the path of flying insects. The number of radii, or spokes, differs with the different species of spiders, and they are usually fastened to a silken framework, which in turn is fastened by guy-lines to surrounding objects. These radii or spokes are connected by a continuous spiral line, spaced regularly except at the center or hub; this hub or center is of more solid silk, and is usually surrounded by an open space; and it may be merely an irregular network, or it may have wide bands of silk laid across it.

The radii or spokes, the guy-lines, the framework and the center of the web are all made of inelastic silk, which does not adhere to an object that touches it. The spiral line, on the contrary, is very elastic, and adheres to any object brought in contact with it. An insect which touches one of these spirals and tries to escape, becomes entangled in the neighboring lines and is thus held fast until the spider can reach it. If one of these elastic lines be examined with a microscope, it is a most beautiful object. There are strung upon it, like pearls, little drops of sticky fluid, which render it not only elastic but adhesive.

Some species of orb-weavers remain at the center of the web, while others hide in some little retreat near at hand. If in the middle, the spider always keeps watchful claws upon the radii of the web so that if there is any jarring of the structure by an entrapped insect, it is at once apprised of the fact; if the spider is in a den at one side, it keeps a claw upon a trap line which is stretched tightly from the hub of the web to the den, and thus communicates any vibration of the web to the hidden sentinel. When the insect becomes entangled, the spider rushes out and envelops it in a band of silk, which feat it accomplishes, by turning the insect over and over rapidly, meanwhile spinning a broad, silken band which swathes it. It may bite the insect before it begins to swathe it in silk, or afterwards. It usually hangs the swathed insect to the web near where it was caught, until ready to eat it; it then takes the prey to the center of the web, if there is where the spider usually sits, or to its den at one side, if it is a den-making species, and there sucks the insect’s blood, carefully throwing away the hard parts.

Insect Life, Comstock.]

The spider does not become entangled in the web, because, when it runs it steps upon the dry radii and not upon the sticky spiral lines. During the busy season, the spider is likely to make a new web every twenty-four hours, but this depends largely upon whether the web has meanwhile been destroyed by large insects.

The spider’s method of making its first bridge is to place itself upon some high point and, lifting its abdomen in the air, to spin out on the breeze a thread of silk. When this touches any object, it adheres, and the spider draws in the slack until the line is “taut;” it then travels across this bridge, which is to support its web, and makes it stronger by doubling the line. From this line, it stretches other lines by fastening a thread to one point, and then walking along to some other point, spinning the thread as it goes and holding the line clear of the object on which it is walking by means of one of its hind legs. When the right point is reached, it pulls the line tight; fastens it, and then, in a similar fashion, proceeds to make another. It may make its first radius by dropping from its bridge to some point below; then climbing back to the center, it fastens the line for another radius, and spinning as it goes, walks down and out to some other point, holding the thread clear and then pulling it tight before fastening it. Having thus selected the center of the web, it goes back and forth to and from it, spinning lines until all of the radii are completed and fastened at one center. It then starts at the center and spins a spiral, laying it onto the radii to hold them firm. However, the lines of this spiral are farther apart and much more irregular than the final spiral. Thus far, all of the threads the spider has spun are inelastic and not sticky; and this first, or temporary spiral is used by the spider to walk upon when spinning the final spiral. It begins the latter at the outer edge instead of at the center, and works toward the middle. As the second spiral progresses, the spider with its jaws cuts away the spiral which it first made, and which it has used as a scaffolding. A careful observer may often see remnants of this first spiral on the radii between the lines of the permanent spiral. The spider works very rapidly and will complete a web in a very short time. The final spiral is made of the elastic and adhesive silk.

_References_--Comstock’s Manual; Common Spiders, Emerton; The Spider Book, Comstock; Nature’s Craftsmen, McCook.

LESSON CXII

THE ORB-WEB

_Leading thought_--No structure made by a creature lower than man is so exquisitely perfect as the orb-web of the spider.

_Method_--There should be an orb-web where the pupils can observe it, preferably with the spider in attendance.

_Observations_--1. Is the orb-web usually hung horizontally or vertically?

2. Observe the radii, or “spokes,” of the web. How many are there? How are they fastened to surrounding objects? Is each spoke fastened to some object or to a framework of silken lines?

3. Observe the silken thread laid around the spokes. Is it a spiral line or is each circle complete? Are the lines the same distance apart on the outer part of the web as at the center? How many of the circling lines are there?

4. Is the center of the web merely an irregular net, or are there bands of silk put on in zigzag shape?

5. Touch any of the “spokes” lightly with the point of a pencil. Does it adhere to the pencil and stretch out as you pull the pencil away? Touch one of the circling lines with a pencil point, and see if it adheres to the point and is elastic. What is the reason for this difference in the stickiness and elasticity of the different kinds of silk in the orb-web?

6. If an insect touches the web, how does it become more entangled by seeking to get away?

7. Where does the spider stay, at the center of the web or in a little retreat at one side?

8. If an insect becomes entangled in the web, how does the spider discover the fact and act?

9. If the spider sits at the middle of the orb, it has a different method for discovering when an insect strikes the web than does the spider that hides in a den at one side. Describe the methods of each.

10. How does the spider make fast an insect? Does it bite the insect before it envelops it in silk? Where does it carry the insect to feed upon it?

11. How does the spider manage to run about its web without becoming entangled in the sticky thread? How often does the orb-weaver make a new web?

a, the temporary spiral stay line; b, the sticky spiral line; c, the fragments of the temporary spiral hanging to a radius.

Comstock’s Manual.]

_How an Orb-web is Made_

Spiders may be seen making their webs in the early morning or in the evening. Find an orb-web with a spider in attendance; break the web without frightening the spider and see it replace it in the early evening, or in the morning about daybreak. An orb-weaver may be brought into the house on its web, when the web is on a branch, and placed where it will not be disturbed, and thus be watched at leisure.

_Observations_--1. How does the spider manage to place the supporting line between two points?

2. How does it make the framework for holding the web in place?

3. How does it make the first radius?

4. How does it make the other radii and select the point which is to be the center of the web?

_The zigzag strengthening band at center of an orb-web._ ]

5. How does it keep the line which it is spinning clear of the line it walks upon?

6. After the radii are all made, are they fastened at the center?

7. How and where does the spider first begin to spin a spiral? Are the lines of this spiral close together or far apart? For what is the first spiral used?

8. Where does it begin to spin the permanent spiral? Where does it walk when spinning it? By the way it walks on the first spiral, do you think it is sticky and elastic? What does it do with the first spiral while the second one is being finished?

9. If the center of the web has a zigzag ribbon of silk, when was it put on?

10. How many minutes did it take the spider to complete the web?

_Supplementary reading_--“Argiope of The Silver Shield,” Insect Stories, Kellogg.

Photo by J. H. Comstock.]

THE FILMY DOME

_Teacher’s Story_

Like bubbles cut in half, these delicate domes catch the light rays and separate them like a prism into waves of rainbow colors. One of these domes is usually about the size of an ordinary bowl, and is suspended with the opening on the lower side. It is held in place by many guy-lines which attach it to surrounding objects. Above a filmy dome are always stretched many crisscrossed threads for some distance up. These are for the purpose of hindering the flight of insects, so that they will fall into the web. The little spider, which always hangs, back downward, just below the center of the dome, rushes to its prey from the lower side, pulls it through the meshes of the web, and feeds upon it. But any remains of the insect or pieces of sticks or leaves which may drop upon the web, it carefully cuts out and drops to the ground, mending the hole very neatly.

LESSON CXIII

THE FILMY DOME

_Leading thought_--One little spider spins a filmy dome, beneath the apex of which it hangs, back downward, awaiting its prey.

_Method_--On a sunny day in late summer or early autumn, while walking along woodland paths, the careful observer is sure to see suspended among the bushes or in the tops of weeds, or among dead branches of young hemlocks, the filmy dome webs. They are about as large as a small bowl, and usually so delicate that they cannot be seen unless the sun shines upon them; they are likely to be exquisitely iridescent under the sun’s rays. Such a dome may be studied by a class or by the pupils individually.

_Observations_--1. Where did you discover the filmy dome? What is the size of the dome? Does it open above or below? How is it held in place?

2. Are there many crisscrossed threads extending above the dome? If so, what do you think they are for?

3. Where does the spider stay? Is the spider large and heavy, or small and delicate?

4. What does the spider do if an insect becomes entangled in its web?

5. Throw a bit of stick or leaf upon a filmy dome web, and note what becomes of it.

* * * * *

“_With spiders I had friendship made,
And watch’d them in their sullen trade._”
--PRISONER OF CHILLON.

BALLOONING SPIDERS

_Teacher’s Story_

If we look across the grass some warm sunny morning or evening of early fall, we see threads of spider silk clinging everywhere; these are not regular webs for trapping insects, but are single threads spun from grass stalk to grass stalk until the fields are carpeted with glistening silk. We have a photograph of a plowed field, taken in autumn, which looks likes the waves of a lake; so completely is the ground covered with spider threads that it shows the “path of the sun” like water.

When we see so many of these random threads, it is a sign that the young spiders have started on their travels, and it is not difficult then to find one in the act. The spiderling climbs up some tall object, like a twig or a blade of grass, and sends out its thread of silk upon the air. If the thread becomes entangled, the spiderling sometimes walks off on it, using it as a bridge, or sometimes it begins again. If the thread does not become entangled with any object, there is soon enough given off, so that the friction of the air current upon it supports the weight of the body of the little creature, which promptly lets go its hold of earth as soon as it feels safely buoyed up, and off it floats to lands unknown. Spiders thus sailing through the air have been discovered in mid-ocean.

Thus we see that the spiders have the same way of distributing their species over the globe, as have the thistles and dandelions. It has been asked what the spiders live upon while they are making these long journeys, especially those that have drifted out to sea. The spider has very convenient habits of eating. When it finds plenty of food it eats a great deal; but in time of famine it lives on, apparently comfortably, without eating. One of our captive spiders was mislaid for six months and when we found her she was as full of “grit” as ever, and she did not seem to be abnormally hungry when food was offered her.

* * * * *

“_A noiseless, patient spider,
I mark’d where, on a little promontory, it stood isolated:
Mark’d how to explore the vacant, vast surrounding,
It launch’d forth filament out of itself:
Ever unreeling them--ever tirelessly speeding them._

“_And you, O my soul, where you stand,
Surrounded, surrounded, in measureless oceans of space,
Ceaselessly, musing, venturing, throwing, seeking the spheres
to connect them;
Till the bridge you will need be form’d--till the ductile
anchor hold;
Till the gossamer thread you fling catch somewhere, O my
soul._”
--WALT WHITMAN.

LESSON CXIV

BALLOONING SPIDERS

_Leading thought_--The young of many species of spiders scatter themselves like thistle seeds in balloons which they make of silk.

_Method_--These observations should be made out of doors during some warm sunny day in October. Read Nature’s Craftsmen, McCook, p. 182.

_Observations_--1. Look across the grass some warm sunny morning or evening of early fall, and note the threads of spider silk gleaming everywhere, not regular webs, but single threads spun from grass stalk to grass stalk, or from one object to another, until the ground seems glistening with silk threads.

2. Find a small spider on a bush, fence post, or at the top of some tall grass stalk; watch it until it begins to spin out its thread.

3. What happens to the thread as it is spun out?

4. If the thread does not become entangled in any surrounding object what happens? If the thread does become entangled, what happens?

5. How far do you suppose a spider can travel on this silken aeroplane? Why should the young spider wish to travel?

THE WHITE CRAB-SPIDER

_Teacher’s Story_

There are certain spiders which are crablike in form, and their legs are so arranged that they can walk more easily sidewise or backward than forward. These spiders spin no webs, but lie in wait for their prey. Many of them live upon plants and fences and, in winter, hide in protected places.

The white crab-spider is a little rascal that has discovered the advantage of protective coloring as a means of hiding itself from the view of its victims, until too late to save themselves; the small assassin always takes on the color of the flower in which it lies concealed. In the white trillium, it is greenish white; while in the golden-rod its decorations are yellow. It waits in the heart of the flower, or in the flower clusters, until the visiting insect alights and seeks to probe for the nectar; it then leaps forward and fastens its fangs into its struggling victim. I have seen a crab-spider in a milkweed attack a bee three times its size. This spider was white with lilac or purple markings. If disturbed, the crab-spider can walk off awkwardly or it may drop by a silken thread. It is especially interesting, since it illustrates another use for protective coloring; and also because this species seems to be able to change its colors to suit its surroundings.

LESSON CXV

THE WHITE CRAB-SPIDER

_Leading thought_--1. The white crab spider has markings upon its body of the same color as the flower in which it rests and is thus enabled to hide in ambush out of the sight of its victims--the insects which come to the flower for nectar.

_Method_--Ask the children to bring one of these spiders to school in the flower in which it was found; note how inconspicuous it is, and arouse an interest in the different colors which these spiders assume in different flowers.

_Observations_--1. What is the shape of the body of the crab-spider? Which of the legs are the longest? Are these legs directed forward or backward?

2. How is the body marked? What colors do you find upon it? Are the colors the same in the spiders found in the trilliums, as those in other flowers? Why is this? Do you think that the color of the spider keeps it from being seen?

3. Place the white spider which you may find in a trillium in a daffodil, and note if the color changes.

4. Do the crab-spiders make webs? How do they trap their prey?

This species is white when lurking in the white trillium and yellow when among flowers of the golden-rod.

Photo by Slingerland.]

HOW THE SPIDER MOTHERS TAKE CARE OF THEIR EGGS

_Teacher’s Story_

Protecting her eggs from the vicissitudes of the weather seems to be the spider mother’s chief care; though at the same time and by the same means, she protects them from the attacks of predacious insects. Many of the species make silken egg-sacs, which are often elaborate in construction, and are carefully placed in protected situations.

Often a little silvery disk may be seen attached to a stone in a field. It resembles a circular lichen on the stone, but if it is examined it is found to consist of an upper, very smooth, waterproof coat, while below is a soft, downy nest, completely enfolding the spider’s eggs.

The egg-sacs of the cobweb weavers are often found suspended in their webs. One of the large orbweavers makes a very remarkable nest, which it attaches to the branches of weeds or shrubs. This sac is about as large as a hickory nut, and opens like a vase at the top. It is very securely suspended by many strong threads of silk, so that the blasts of winter cannot tear it loose. The outside is shining and waterproof, while inside it has a fit lining for a spiderling cradle.

Dr. Burt G. Wilder studied the development of the inmates of one of these nests by cutting open different nests at different periods of the winter. In the autumn, the nest contained five hundred or more eggs. These eggs hatched in early winter but it seemed foreordained that some of the little spiders were born for food for their stronger brethren. They seemed resigned to their fate, for when one of these victims was seized by its cannibalistic brother, it curled up its legs and submitted meekly. The result of this process was that, out of the five hundred little spiders hatched from the eggs, only a few healthy and apparently happy young spiders emerged from the nest in the spring, sustained by the nourishment afforded them by their own family, and fitted for their life in the outside world.

Some spiders make a nest for their eggs within folded leaves, and some build them in crevices of rocks and boards.

The running spiders, which are the large ones found under stones, make globular egg-sacs; the mother spider drags after her this egg-sac attached to her spinnerets; the young, when they hatch, climb upon their mother’s back, and there remain for a time.

LESSON CXVI

THE NESTS OF SPIDERS

_Leading thought_--The spider mothers have many interesting ways of protecting their eggs, which they envelop in silken sacs and place in safety.

_Method_--Ask the pupils to bring in all the spider egg-sacs that they can find. Keep some of them unopened, and open others of the same kind, and thus discover how many eggs are in the sac, and how many spiderlings come out. This is a good lesson for September and October.

_Observations_--1. In what situation did you find the nest? How was it protected from rain and snow? To what was it attached?

2. Of what texture is the outside of the sac? Is the outside made of waterproof silk? What is the texture of the lining?

3. How many eggs in this sac? What is the color of the eggs? When do the spiderlings hatch? Do as many spiders come out of the sac as there were eggs? Why is this?

Photo by Slingerland.]