Soon we see a few Spiders trotting briskly between the table and the open window. They are running in mid-air. But on what? If the light fall favourably, I manage to see, at moments, behind the tiny animal, a thread resembling a ray of light, which appears for an instant, gleams and disappears. Behind, there is a mooring, only just perceptible, if you look very carefully; but, in front, towards the window, there is nothing to be seen at all.

In vain I examine above, below, at the side; in vain I vary the direction of the eye: I can distinguish no support for the little creature to walk upon. One would think that the beastie were paddling in space. It suggests the idea of a small bird, tied by the leg with a thread and making a flying rush forwards.

But, in this case, appearances are deceptive: flight is impossible; the Spider must necessarily have a bridge whereby to cross the intervening space. This bridge, which I cannot see, I can at least destroy. I cleave the air with a ruler in front of the Spider making for the window. That is quite enough: the tiny animal at once ceases to go forward and falls. The invisible foot-plank is broken. My son, young Paul, who is helping me, is astounded at this wave of the magic wand, for not even he, with his fresh, young eyes, is able to see a support ahead for the Spiderling to move along.

In the rear, on the other hand, a thread is visible. The difference is easily explained. Every Spider, as she goes, at the same time spins a safety-cord which will guard the rope-walker against the risk of an always possible fall. In the rear, therefore, the thread is of double thickness and can be seen, whereas, in front, it is still single and hardly perceptible to the eye.

Obviously, this invisible foot-bridge is not flung out by the animal: it is carried and unrolled by a gust of air. The Epeira, supplied with this line, lets it float freely; and the wind, however softly blowing, bears it along and unwinds it. Even so is the smoke from the bowl of a pipe whirled up in the air.

This floating thread has but to touch any object in the neighbourhood and it will remain fixed to it. The suspension-bridge is thrown; and the Spider can set out. The South-American Indians are said to cross the abysses of the Cordilleras in travelling-cradles made of twisted creepers; the little Spider passes through space on the invisible and the imponderable.

But to carry the end of the floating thread elsewhither a draught is needed. At this moment, the draught exists between the door of my study and the window, both of which are open. It is so slight that I do not feel its; I only know of it by the smoke from my pipe, curling softly in that direction. Cold air enters from without through the door; warm air escapes from the room through the window. This is the drought that carries the threads with it and enables the Spiders to embark upon their journey.

I get rid of it by closing both apertures and I break off any communication by passing my ruler between the window and the table. Henceforth, in the motionless atmosphere, there are no departures. The current of air is missing, the skeins are not unwound and migration becomes impossible.

It is soon resumed, but in a direction whereof I never dreamt. The hot sun is beating on a certain part of the floor. At this spot, which is warmer than the rest, a column of lighter, ascending air is generated. If this column catch the threads, my Spiders ought to rise to the ceiling of the room.

The curious ascent does, in fact, take place. Unfortunately, my troop, which has been greatly reduced by the number of departures through the window, does not lend itself to prolonged experiment. We must begin again.

The next morning, on the same yucca, I gather the second family, as numerous as the first. Yesterday's preparations are repeated. My legion of Spiders first weaves a divergent framework between the top of the brushwood placed at the emigrants' disposal and the edge of the table. Five or six hundred wee beasties swarm all over this work-yard.

While this little world is busily fussing, making its arrangements for departure, I make my own. Every aperture in the room is closed, so as to obtain as calm an atmosphere as possible. A small chafing-dish is lit at the foot of the table. My hands cannot feel the heat of it at the level of the web whereon my Spiders are weaving. This is the very modest fire which, with its column of rising air, shall unwind the threads and carry them on high.

Let us first enquire the direction and strength of the current. Dandelion-plumes, made lighter by the removal of their seeds, serve as my guides. Released above the chafing-dish, on the level of the table, they float slowly upwards and, for the most part, reach the ceiling. The emigrants' lines should rise in the same way and even better.

The thing is done: with the aid of nothing that is visible to the three of us looking on, a Spider makes her ascent. She ambles with her eight legs through the air; she mounts, gently swaying. The others, in ever-increasing numbers, follow, sometimes by different roads, sometimes by the same road. Any one who did not possess the secret would stand amazed at this magic ascent without a ladder. In a few minutes, most of them are up, clinging to the ceiling.

Not all of them reach it. I see some who, on attaining a certain height, cease to go up and even lose ground, although moving their legs forward with all the nimbleness of which they are capable. The more they struggle upwards, the faster they come down. This drifting, which neutralizes the distance covered and even converts it into a retrogression, is easily explained.

The thread has not reached the platform; it floats, it is fixed only at the lower end. As long as it is of a fair length, it is able, although moving, to bear the minute animal's weight. But, as the Spider climbs, the float becomes shorter in proportion; and the time comes when a balance is struck between the ascensional force of the thread and the weight carried. Then the beastie remains stationary, although continuing to climb.

Presently, the weight becomes too much for the shorter and shorter float; and the Spider slips down, in spite of her persistent, forward striving. She is at last brought back to the branch by the falling threads. Here, the ascent is soon renewed, either on a fresh thread, if the supply of silk be not yet exhausted, or on a strange thread, the work, of those who have gone before.

As a rule, the ceiling is reached. It is twelve feet high. The little Spider is able, therefore, as the first product of her spinning-mill, before taking any refreshment, to obtain a line fully twelve feet in length. And all this, the rope-maker and her rope, was contained in the egg, a particle of no size at all. To what a degree of fineness can the silky matter be wrought wherewith the young Spider is provided! Our manufacturers are able to turn out platinum-wire that can only be seen when it is made red-hot. With much simpler means, the Spiderling draws from her wire-mill threads so delicate that, even the brilliant light of the sun does not always enable us to discern them.

We must not let all the climbers be stranded on the ceiling, an inhospitable region where most of them will doubtless perish, being unable to produce a second thread before they have had a meal. I open the window. A current of lukewarm air, coming from the chafing-dish, escapes through the top. Dandelion-plumes, taking that direction, tell me so. The wafting threads cannot fail to be carried by this flow of air and to lengthen out in the open, where a light breeze is blowing.

I take a pair of sharp scissors and, without shaking the threads, cut a few that are just visible at the base, where they are thickened with an added strand. The result of this operation is marvellous. Hanging to the flying-rope, which is borne on the wind outside, the Spider passes through the window, suddenly flies off and disappears. An easy way of travelling, if the conveyance possessed a rudder that allowed the passenger to land where he pleases! But the little things are at the mercy of the winds: where will they alight? Hundreds, thousands of yards away, perhaps. Let us wish them a prosperous journey.

The problem of dissemination is now solved. What would happen if matters, instead of being brought about by my wiles, took place in the open fields? The answer is obvious. The young Spiders, born acrobats and rope-walkers, climb to the top of a branch so as to find sufficient space below them to unfurl their apparatus. Here, each draws from her rope-factory a thread which she abandons to the eddies of the air. Gently raised by the currents that ascend from the ground warmed by the sun, this thread wafts upwards, floats, undulates, makes for its point of contact. At last, it breaks and vanishes in the distance, carrying the spinstress hanging to it.

The Epeira with the three white crosses, the Spider who has supplied us with these first data concerning the process of dissemination, is endowed with a moderate maternal industry. As a receptacle for the eggs, she weaves a mere pill of silk. Her work is modest indeed beside the Banded Epeira's balloons. I looked to these to supply me with fuller documents. I had laid up a store by rearing some mothers during the autumn. So that nothing of importance might escape me, I divided my stock of balloons, most of which were woven before my eyes, into two sections. One half remained in my study, under a wire-gauze cover, with, small bunches of brushwood as supports; the other half were experiencing the vicissitudes of open-air life on the rosemaries in the enclosure.

These preparations, which promised so well, did not provide me with the sight which I expected, namely, a magnificent exodus, worthy of the tabernacle occupied. However, a few results, not devoid of interest, are to be noted. Let us state them briefly.

The hatching takes place as March approaches. When this time comes, let us open the Banded Epeira's nest with the scissors. We shall find that some of the youngsters have already left the central chamber and scattered over the surrounding eiderdown, while the rest of the laying still consists of a compact mass of orange eggs. The appearance of the younglings is not simultaneous; it takes place with intermissions and may last a couple of weeks.