A special thread, the foundation of the real net, is stretched across the area so capriciously circumscribed. It is distinguished from the others by its isolation, its position at a distance from any twig that might interfere with its swaying length. It never fails to have, in the middle, a thick white point, formed of a little silk cushion. This is the beacon that marks the centre of the future edifice, the post that will guide the Epeira and bring order into the wilderness of twists and turns.
The time has come to weave the hunting-snare. The Spider starts from the centre, which bears the white signpost, and, running along the transversal thread, hurriedly reaches the circumference, that is to say, the irregular frame enclosing the free space. Still with the same sudden movement, she rushes from the circumference to the centre; she starts again backwards and forwards, makes for the right, the left, the top, the bottom; she hoists herself up, dives down, climbs up again, runs down and always returns to the central landmark by roads that slant in the most unexpected manner. Each time, a radius or spoke is laid, here, there, or elsewhere, in what looks like mad disorder.
The operation is so erratically conducted that it takes the most unremitting attention to follow it at all. The Spider reaches the margin of the area by one of the spokes already placed. She goes along this margin for some distance from the point at which she landed, fixes her thread to the frame and returns to the centre by the same road which she has just taken.
The thread obtained on the way in a broken line, partly on the radius and partly on the frame, is too long for the exact distance between the circumference and the central point. On returning to this point, the Spider adjusts her thread, stretches it to the correct length, fixes it and collects what remains on the central signpost. In the case of each radius laid, the surplus is treated in the same fashion, so that the signpost continues to increase in size. It was first a speck; it is now a little pellet, or even a small cushion of a certain breadth.
We shall see presently what becomes of this cushion whereon the Spider, that niggardly housewife, lays her saved-up bits of thread; for the moment, we will note that the Epeira works it up with her legs after placing each spoke, teazles it with her claws, mats it into felt with noteworthy diligence. In so doing, she gives the spokes a solid common support, something like the hub of our carriage-wheels.
The eventual regularity of the work suggests that the radii are spun in the same order in which they figure in the web, each following immediately upon its next neighbour. Matters pass in another manner, which at first looks like disorder, but which is really a judicious contrivance. After setting a few spokes in one direction, the Epeira runs across to the other side to draw some in the opposite direction.
These sudden changes of course are highly logical; they show us how proficient the Spider is in the mechanics of rope-construction. Were they to succeed one another regularly, the spokes of one group, having nothing as yet to counteract them, would distort the work by their straining, would even destroy it for lack of a stabler support. Before continuing, it is necessary to lay a converse group which will maintain the whole by its resistance. Any combination of forces acting in one direction must be forthwith neutralized by another in the opposite direction. This is what our statics teach us and what the Spider puts into practice; she is a past mistress of the secrets of rope-building, without serving an apprenticeship.
One would think that this interrupted and apparently disordered labour must result in a confused piece of work. Wrong: the rays are equidistant and form a beautifully-regular orb. Their number is a characteristic mark of the different species. The Angular Epeira places 21 in her web, the Banded Epeira 32, the Silky Epeira 42. These numbers are not absolutely fixed; but the variation is very slight.
Now which of us would undertake, off-hand, without much preliminary experiment and without measuring-instruments, to divide a circle into a given quantity of sectors of equal width? The Epeirae, though weighted with a wallet and tottering on threads shaken by the wind, effect the delicate division without stopping to think. They achieve it by a method which seems mad according to our notions of geometry. Out of disorder they evolve order.
We must not, however, give them more than their due. The angles are only approximately equal; they satisfy the demands of the eye, but cannot stand the test of strict measurement. Mathematical precision would be superfluous here. No matter, we are amazed at the result obtained. How does the Epeira come to succeed with her difficult problem, so strangely managed? I am still asking myself the question.
The laying of the radii is finished. The Spider takes her place in the centre, on the little cushion formed of the inaugural signpost and the bits of thread left over. Stationed on this support, she slowly turns round and round. She is engaged on a delicate piece of work. With an extremely thin thread, she describes from spoke to spoke, starting from the centre, a spiral line with very close coils. The central space thus worked attains, in the adults' webs, the dimensions of the palm of one's hand; in the younger Spiders' webs, it is much smaller, but it is never absent. For reasons which I will explain in the course of this study, I shall call it, in future, the 'resting-floor.'
The thread now becomes thicker. The first could hardly be seen; the second is plainly visible. The Spider shifts her position with great slanting strides, turns a few times, moving farther and farther from the centre, fixes her line each time to the spoke which she crosses and at last comes to a stop at the lower edge of the frame. She has described a spiral with coils of rapidly-increasing width. The average distance between the coils, even in the structures of the young Epeirae, is one centimetre. {29}
Let us not be misled by the word 'spiral,' which conveys the notion of a curved line. All curves are banished from the Spiders' work; nothing is used but the straight line and its combinations. All that is aimed at is a polygonal line drawn in a curve as geometry understands it. To this polygonal line, a work destined to disappear as the real toils are woven, I will give the name of the 'auxiliary spiral.' Its object is to supply cross-bars, supporting rungs, especially in the outer zone, where the radii are too distant from one another to afford a suitable groundwork.
Its object is also to guide the Epeira in the extremely delicate business which she is now about to undertake.
But, before that, one last task becomes essential. The area occupied by the spokes is very irregular, being marked out by the supports of the branch, which are infinitely variable. There are angular niches which, if skirted too closely, would disturb the symmetry of the web about to be constructed. The Epeira needs an exact space wherein gradually to lay her spiral thread. Moreover, she must not leave any gaps through which her prey might find an outlet.
An expert in these matters, the Spider soon knows the corners that have to be filled up. With an alternating movement, first in this direction, then in that, she lays, upon the support of the radii, a thread that forms two acute angles at the lateral boundaries of the faulty part and describes a zigzag line not wholly unlike the ornament known as the fret.
The sharp corners have now been filled with frets on every side; the time has come to work at the essential part, the snaring-web for which all the rest is but a support. Clinging on the one hand to the radii, on the other to the chords of the auxiliary spiral, the Epeira covers the same ground as when laying the spiral, but in the opposite direction: formerly, she moved away from the centre; now she moves towards it and with closer and more numerous circles. She starts from the base of the auxiliary spiral, near the frame.
What follows is difficult to observe, for the movements are very quick and spasmodic, consisting of a series of sudden little rushes, sways and bends that bewilder the eye. It needs continuous attention and repeated examination to distinguish the progress of the work however slightly.
The two hind-legs, the weaving implements, keep going constantly. Let us name them according to their position on the work-floor. I call the leg that faces the centre of the coil, when the animal moves, the 'inner leg;' the one outside the coil the 'outer leg.'
The latter draws the thread from the spinneret and passes it to the inner leg, which, with a graceful movement, lays it on the radius crossed. At the same time, the first leg measures the distance; it grips the last coil placed in position and brings within a suitable range that point of the radius whereto the thread is to be fixed. As soon as the radius is touched, the thread sticks to it by its own glue. There are no slow operations, no knots: the fixing is done of itself.
Meanwhile, turning by narrow degrees, the spinstress approaches the auxiliary chords that have just served as her support. When, in the end, these chords become too close, they will have to go; they would impair the symmetry of the work. The Spider, therefore, clutches and holds on to the rungs of a higher row; she picks up, one by one, as she goes along, those which are of no more use to her and gathers them into a fine- spun ball at the contact-point of the next spoke. Hence arises a series of silky atoms marking the course of the disappearing spiral.
The light has to fall favourably for us to perceive these specks, the only remains of the ruined auxiliary thread. One would take them for grains of dust, if the faultless regularity of their distribution did not remind us of the vanished spiral. They continue, still visible, until the final collapse of the net.
And the Spider, without a stop of any kind, turns and turns and turns, drawing nearer to the centre and repeating the operation of fixing her thread at each spoke which she crosses. A good half-hour, an hour even among the full-grown Spiders, is spent on spiral circles, to the number of about fifty for the web of the Silky Epeira and thirty for those of the Banded and the Angular Epeira.
At last, at some distance from the centre, on the borders of what I have called the resting-floor, the Spider abruptly terminates her spiral when the space would still allow of a certain number of turns. We shall see the reason of this sudden stop presently. Next, the Epeira, no matter which, young or old, hurriedly flings herself upon the little central cushion, pulls it out and rolls it into a ball which I expected to see thrown away. But no: her thrifty nature does not permit this waste. She eats the cushion, at first an inaugural landmark, then a heap of bits of thread; she once more melts in the digestive crucible what is no doubt intended to be restored to the silken treasury. It is a tough mouthful, difficult for the stomach to elaborate; still, it is precious and must not be lost. The work finishes with the swallowing. Then and there, the Spider instals herself, head downwards, at her hunting-post in the centre of the web.
The operation which we have just seen gives rise to a reflection. Men are born right-handed. Thanks to a lack of symmetry that has never been explained, our right side is stronger and readier in its movements than our left. The inequality is especially noticeable in the two hands. Our language expresses this supremacy of the favoured side in the terms dexterity, adroitness and address, all of which allude to the right hand.
Is the animal, on its side, right-handed, left-handed, or unbiased? We have had opportunities of showing that the Cricket, the Grasshopper and many others draw their bow, which is on the right wing-case, over the sounding apparatus, which is on the left wing-case. They are right-handed.
When you and I take an unpremeditated turn, we spin round on our right heel. The left side, the weaker, moves on the pivot of the right, the stronger. In the same way, nearly all the Molluscs that have spiral shells roll their coils from left to right. Among the numerous species in both land and water fauna, only a very few are exceptional and turn from right to left.
It would be interesting to try and work out to what extent that part of the zoological kingdom which boasts a two-sided structure is divided into right-handed and left-handed animals. Can dissymetry, that source of contrasts, be a general rule? Or are there neutrals, endowed with equal powers of skill and energy on both sides? Yes, there are; and the Spider is one of them. She enjoys the very enviable privilege of possessing a left side which is no less capable than the right. She is ambidextrous, as witness the following observations.
When laying her snaring-thread, every Epeira turns in either direction indifferently, as a close watch will prove. Reasons whose secret escapes us determine the direction adopted. Once this or the other course is taken, the spinstress does not change it, even after incidents that sometimes occur to disturb the progress of the work. It may happen that a Gnat gets caught in the part already woven. The Spider thereupon abruptly interrupts her labours, hastens up to the prey, binds it and then returns to where she stopped and continues the spiral in the same order as before.
At the commencement of the work, gyration in one direction being employed as well as gyration in the other, we see that, when making her repeated webs, the same Epeira turns now her right side, now her left to the centre of the coil. Well, as we have said, it is always with the inner hind-leg, the leg nearer the centre, that is to say, in some cases the right and in some cases the left leg, that she places the thread in position, an exceedingly delicate operation calling for the display of exquisite skill, because of the quickness of the action and the need for preserving strictly equal distances. Any one seeing this leg working with such extreme precision, the right leg to-day, the left to-morrow, becomes convinced that the Epeira is highly ambidextrous.
CHAPTER X: THE GARDEN SPIDERS: MY NEIGHBOUR
Age does not modify the Epeira's talent in any essential feature. As the young worked, so do the old, the richer by a year's experience. There are no masters nor apprentices in their guild; all know their craft from the moment that the first thread is laid. We have learnt something from the novices: let us now look into the matter of their elders and see what additional task the needs of age impose upon them.
July comes and gives me exactly what I wish for. While the new inhabitants are twisting their ropes on the rosemaries in the enclosure, one evening, by the last gleams of twilight, I discover a splendid Spider, with a mighty belly, just outside my door. This one is a matron; she dates back to last year; her majestic corpulence, so exceptional at this season, proclaims the fact. I know her for the Angular Epeira (_Epeira angulata_, WALCK.), clad in grey and girdled with two dark stripes that meet in a point at the back. The base of her abdomen swells into a short nipple on either side.
This neighbour will certainly serve my turn, provided that she do not work too late at night. Things bode well: I catch the buxom one in the act of laying her first threads. At this rate my success need not be won at the expense of sleep. And, in fact, I am able, throughout the month of July and the greater part of August, from eight to ten o'clock in the evening, to watch the construction of the web, which is more or less ruined nightly by the incidents of the chase and built up again, next day, when too seriously dilapidated.
During the two stifling months, when the light fails and a spell of coolness follows upon the furnace-heat of the day, it is easy for me, lantern in hand, to watch my neighbour's various operations. She has taken up her abode, at a convenient height for observation, between a row of cypress-trees and a clump of laurels, near the entrance to an alley haunted by Moths. The spot appears well-chosen, for the Epeira does not change it throughout the season, though she renews her net almost every night.
Punctually as darkness falls, our whole family goes and calls upon her.
Big and little, we stand amazed at her wealth of belly and her exuberant somersaults in the maze of quivering ropes; we admire the faultless geometry of the net as it gradually takes shape. All agleam in the lantern-light, the work becomes a fairy orb, which seems woven of moonbeams.
Should I linger, in my anxiety to clear up certain details, the household, which by this time is in bed, waits for my return before going to sleep:
'What has she been doing this evening?' I am asked. 'Has she finished her web? Has she caught a Moth?'
I describe what has happened. To-morrow, they will be in a less hurry to go to bed: they will want to see everything, to the very end. What delightful, simple evenings we have spent looking into the Spider's workshop!
The journal of the Angular Epeira, written up day by day, teaches us, first of all, how she obtains the ropes that form the framework of the building. All day invisible, crouching amid the cypress-leaves, the Spider, at about eight o'clock in the evening, solemnly emerges from her retreat and makes for the top of a branch. In this exalted position, she sits for some time laying her plans with due regard to the locality; she consults the weather, ascertains if the night will be fine. Then, suddenly, with her eight legs wide-spread, she lets herself drop straight down, hanging to the line that issues from her spinnerets. Just as the rope-maker obtains the even output of his hemp by walking backwards, so does the Epeira obtain the discharge of hers by falling. It is extracted by the weight of her body.
The descent, however, has not the brute speed which the force of gravity would give it, if uncontrolled. It is governed by the action of the spinnerets, which contract or expand their pores, or close them entirely, at the faller's pleasure. And so, with gentle moderation she pays out this living plumb-line, of which my lantern clearly shows me the plumb, but not always the line. The great squab seems at such times to be sprawling in space, without the least support.
She comes to an abrupt stop two inches from the ground; the silk-reel ceases working. The Spider turns round, clutches the line which she has just obtained and climbs up by this road, still spinning. But, this time, as she is no longer assisted by the force of gravity, the thread is extracted in another manner. The two hind-legs, with a quick alternate action, draw it from the wallet and let it go.
On returning to her starting-point, at a height of six feet or more, the Spider is now in possession of a double line, bent into a loop and floating loosely in a current of air. She fixes her end where it suits her and waits until the other end, wafted by the wind, has fastened its loop to the adjacent twigs.
The desired result may be very slow in coming. It does not tire the unfailing patience of the Epeira, but it soon wears out mine. And it has happened to me sometimes to collaborate with the Spider. I pick up the floating loop with a straw and lay it on a branch, at a convenient height. The foot-bridge erected with my assistance is considered satisfactory, just as though the wind had placed it. I count this collaboration among the good actions standing to my credit.
Feeling her thread fixed, the Epeira runs along it repeatedly, from end to end, adding a fibre to it on each journey. Whether I help or not, this forms the 'suspension-cable,' the main piece of the framework. I call it a cable, in spite of its extreme thinness, because of its structure. It looks as though it were single, but, at the two ends, it is seen to divide and spread, tuft-wise, into numerous constituent parts, which are the product of as many crossings. These diverging fibres, with their several contact-points, increase the steadiness of the two extremities.
The suspension-cable is incomparably stronger than the rest of the work and lasts for an indefinite time. The web is generally shattered after the night's hunting and is nearly always rewoven on the following evening. After the removal of the wreckage, it is made all over again, on the same site, cleared of everything except the cable from which the new network is to hang.
The laying of this cable is a somewhat difficult matter, because the success of the enterprise does not depend upon the animal's industry alone. It has to wait until a breeze carries the line to the pier-head in the bushes. Sometimes, a calm prevails; sometimes, the thread catches at an unsuitable point. This involves great expenditure of time, with no certainty of success. And so, when once the suspension-cable is in being, well and solidly placed, the Epeira does not change it, except on critical occasions. Every evening, she passes and repasses over it, strengthening it with fresh threads.
When the Epeira cannot manage a fall of sufficient depth to give her the double line with its loop to be fixed at a distance, she employs another method. She lets herself down and then climbs up again, as we have already seen; but, this time, the thread ends suddenly in a filmy hair- pencil, a tuft, whose parts remain disjoined, just as they come from the spinneret's rose. Then this sort of bushy fox's brush is cut short, as though with a pair of scissors, and the whole thread, when unfurled, doubles its length, which is now enough for the purpose. It is fastened by the end joined to the Spider; the other floats in the air, with its spreading tuft, which easily tangles in the bushes. Even so must the Banded Epeira go to work when she throws her daring suspension-bridge across a stream.