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THE SPIDERS' EXODUS




Seeds, when ripened in the fruit, are disseminated, that is to say,
scattered on the surface of the ground, to sprout in spots as yet
unoccupied and fill the expanses that realize favourable conditions.

Amid the wayside rubbish grows one of the gourd family, _Ecbalium
elaterium_, commonly called the squirting cucumber, whose fruit--a rough
and extremely bitter little cucumber--is the size of a date. When ripe,
the fleshy core resolves into a liquid in which float the seeds.
Compressed by the elastic rind of the fruit, this liquid bears upon the
base of the footstalk, which is gradually forced out, yields like a
stopper, breaks off and leaves an orifice through which a stream of seeds
and fluid pulp is suddenly ejected. If, with a novice hand, under a
scorching sun, you shake the plant laden with yellow fruit, you are bound
to be somewhat startled when you hear a noise among the leaves and
receive the cucumber's grapeshot in your face.

The fruit of the garden balsam, when ripe, splits, at the least touch,
into five fleshy valves, which curl up and shoot their seeds to a
distance. The botanical name of _Impatiens_ given to the balsam alludes
to this sudden dehiscence of the capsules, which cannot endure contact
without bursting.

In the damp and shady places of the woods there exists a plant of the
same family which, for similar reasons, bears the even more expressive
name of _Impatiens noli-me-tangere_, or touch-me-not.

The capsule of the pansy expands into three valves, each scooped out like
a boat and laden in the middle with two rows of seeds. When these valves
dry, the edges shrivel, press upon the grains and eject them.

Light seeds, especially those of the order of Compositae, have aeronautic
apparatus--tufts, plumes, fly-wheels--which keep them up in the air and
enable them to take distant voyages. In this way, at the least breath,
the seeds of the dandelion, surmounted by a tuft of feathers, fly from
their dry receptacle and waft gently in the air.

Next to the tuft, the wing is the most satisfactory contrivance for
dissemination by wind. Thanks to their membranous edge, which gives them
the appearance of thin scales, the seeds of the yellow wall-flower reach
high cornices of buildings, clefts of inaccessible rocks, crannies in old
walls, and sprout in the remnant of mould bequeathed by the mosses that
were there before them.

The samaras, or keys, of the elm, formed of a broad, light fan with the
seed cased in its centre; those of the maple, joined in pairs and
resembling the unfurled wings of a bird; those of the ash, carved like
the blade of an oar, perform the most distant journeys when driven before
the storm.

Like the plant, the insect also sometimes possesses travelling-apparatus,
means of dissemination that allow large families to disperse quickly over
the country, so that each member may have his place in the sun without
injuring his neighbour; and these apparatus, these methods vie in
ingenuity with the elm's samara, the dandelion-plume and the catapult of
the squirting cucumber.

Let us consider, in particular, the Epeirae, those magnificent Spiders
who, to catch their prey, stretch, between one bush and the next, great
vertical sheets of meshes, resembling those of the fowler. The most
remarkable in my district is the Banded Epeira (_Epeira fasciata_,
WALCK.), so prettily belted with yellow, black and silvery white. Her
nest, a marvel of gracefulness, is a satin bag, shaped like a tiny pear.
Its neck ends in a concave mouthpiece closed with a lid, also of satin.
Brown ribbons, in fanciful meridian waves, adorn the object from pole to
pole.

Open the nest. We have seen, in an earlier chapter, {28} what we find
there; let us retell the story. Under the outer wrapper, which is as
stout as our woven stuffs and, moreover, perfectly waterproof, is a
russet eiderdown of exquisite delicacy, a silky fluff resembling driven
smoke. Nowhere does mother-love prepare a softer bed.

In the middle of this downy mass hangs a fine, silk, thimble-shaped
purse, closed with a movable lid. This contains the eggs, of a pretty
orange-yellow and about five hundred in number.

All things considered, is not this charming edifice an animal fruit, a
germ-casket, a capsule to be compared with that of the plants? Only, the
Epeira's wallet, instead of seeds, holds eggs. The difference is more
apparent than real, for egg and grain are one.

How will this living fruit, ripening in the heat beloved of the Cicadae,
manage to burst? How, above all, will dissemination take place? They
are there in their hundreds. They must separate, go far away, isolate
themselves in a spot where there is not too much fear of competition
among neighbours. How will they set to work to achieve this distant
exodus, weaklings that they are, taking such very tiny steps?

I receive the first answer from another and much earlier Epeira, whose
family I find, at the beginning of May, on a yucca in the enclosure. The
plant blossomed last year. The branching flower-stem, some three feet
high, still stands erect, though withered. On the green leaves, shaped
like a sword-blade, swarm two newly-hatched families. The wee beasties
are a dull yellow, with a triangular black patch upon their stern. Later
on, three white crosses, ornamenting the back, will tell me that my find
corresponds with the Cross or Diadem Spider (_Epeira diadema_, WALCK.).

When the sun reaches this part of the enclosure, one of the two groups
falls into a great state of flutter. Nimble acrobats that they are, the
little Spiders scramble up, one after the other, and reach the top of the
stem. Here, marches and countermarches, tumult and confusion reign, for
there is a slight breeze which throws the troop into disorder. I see no
connected manoeuvres. From the top of the stalk they set out at every
moment, one by one; they dart off suddenly; they fly away, so to speak.
It is as though they had the wings of a Gnat.

Forthwith they disappear from view. Nothing that my eyes can see
explains this strange flight; for precise observation is impossible amid
the disturbing influences out of doors. What is wanted is a peaceful
atmosphere and the quiet of my study.

I gather the family in a large box, which I close at once, and instal it
in the animals' laboratory, on a small table, two steps from the open
window. Apprised by what I have just seen of their propensity to resort
to the heights, I give my subjects a bundle of twigs, eighteen inches
tall, as a climbing-pole. The whole band hurriedly clambers up and
reaches the top. In a few moments there is not one lacking in the group
on high. The future will tell us the reason of this assemblage on the
projecting tips of the twigs.

The little Spiders are now spinning here and there at random: they go up,
go down, come up again. Thus is woven a light veil of divergent threads,
a many-cornered web with the end of the branch for its summit and the
edge of the table for its base, some eighteen inches wide. This veil is
the drill-ground, the work-yard where the preparations for departure are
made.

Here hasten the humble little creatures, running indefatigably to and
fro. When the sun shines upon them, they become gleaming specks and form
upon the milky background of the veil a sort of constellation, a reflex
of those remote points in the sky where the telescope shows us endless
galaxies of stars. The immeasurably small and the immeasurably large are
alike in appearance. It is all a matter of distance.

But the living nebula is not composed of fixed stars; on the contrary,
its specks are in continual movement. The young Spiders never cease
shifting their position on the web. Many let themselves drop, hanging by
a length of thread, which the faller's weight draws from the spinnerets.
Then quickly they climb up again by the same thread, which they wind
gradually into a skein and lengthen by successive falls. Others confine
themselves to running about the web and also give me the impression of
working at a bundle of ropes.

The thread, as a matter of fact, does not flow from the spinneret; it is
drawn thence with a certain effort. It is a case of extraction, not
emission. To obtain her slender cord, the Spider has to move about and
haul, either by falling or by walking, even as the rope-maker steps
backwards when working his hemp. The activity now displayed on the drill-
ground is a preparation for the approaching dispersal. The travellers
are packing up.

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, therefore, 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.

Nothing as yet suggests the future, richly-striped livery. The abdomen
is white and, as it were, floury in the front half; in the other half it
is a blackish-brown. The rest of the body is pale-yellow, except in
front, where the eyes form a black edging. When left alone, the little
ones remain motionless in the soft, russet swan's-down; if disturbed,
they shuffle lazily where they are, or even walk about in a hesitating
and unsteady fashion. One can see that they have to ripen before
venturing outside.

Maturity is achieved in the exquisite floss that surrounds the natal
chamber and fills out the balloon. This is the waiting-room in which the
body hardens. All dive into it as and when they emerge from the central
keg. They will not leave it until four months later, when the midsummer
heats have come.

Their number is considerable. A patient and careful census gives me
nearly six hundred. And all this comes out of a purse no larger than a
pea. By what miracle is there room for such a family? How do those
thousands of legs manage to grow without straining themselves?

The egg-bag, as we learnt in Chapter II., is a short cylinder rounded at
the bottom. It is formed of compact white satin, an insuperable barrier.
It opens into a round orifice wherein is bedded a lid of the same
material, through which the feeble beasties would be incapable of
passing. It is not a porous felt, but a fabric as tough as that of the
sack. Then by what mechanism is the delivery effected?

Observe that the disk of the lid doubles back into a short fold, which
edges into the orifice of the bag. In the same way, the lid of a
saucepan fits the mouth by means of a projecting rim, with this
difference, that the rim is not attached to the saucepan, whereas, in the
Epeira's work, it is soldered to the bag or nest. Well, at the time of
the hatching, this disk becomes unstuck, lifts and allows the new-born
Spiders to pass through.

If the rim were movable and simply inserted, if, moreover, the birth of
all the family took place at the same time, we might think that the door
is forced open by the living wave of inmates, who would set their backs
to it with a common effort. We should find an approximate image in the
case of the saucepan, whose lid is raised by the boiling of its contents.
But the fabric of the cover is one with the fabric of the bag, the two
are closely welded; besides, the hatching is effected in small batches,
incapable of the least exertion. There must, therefore, be a spontaneous
bursting, or dehiscence, independent of the assistance of the youngsters
and similar to that of the seed-pods of plants.

When fully ripened, the dry fruit of the snap-dragon opens three windows;
that of the pimpernel splits into two rounded halves, something like
those of the outer case of a fob-watch; the fruit of the carnation partly
unseals its valves and opens at the top into a star-shaped hatch. Each
seed-casket has its own system of locks, which are made to work smoothly
by the mere kiss of the sun.

Well, that other dry fruit, the Banded Epeira's germ-box, likewise
possesses its bursting-gear. As long as the eggs remain unhatched, the
door, solidly fixed in its frame, holds good; as soon as the little ones
swarm and want to get out, it opens of itself.

Come June and July, beloved of the Cicadae, no less beloved of the young
Spiders who are anxious to be off. It were difficult indeed for them to
work their way through the thick shell of the balloon. For the second
time, a spontaneous dehiscence seems called for. Where will it be
effected?

The idea occurs off-hand that it will take place along the edges of the
top cover. Remember the details given in an earlier chapter. The neck
of the balloon ends in a wide crater, which is closed by a ceiling dug
out cup-wise. The material is as stout in this part as in any other;
but, as the lid was the finishing touch to the work, we expect to find an
incomplete soldering, which would allow it to be unfastened.

The method of construction deceives us: the ceiling is immovable; at no
season can my forceps manage to extract it, without destroying the
building from top to bottom. The dehiscence takes place elsewhere, at
some point on the sides. Nothing informs us, nothing suggests to us that
it will occur at one place rather than another.

Moreover, to tell the truth, it is not a dehiscence prepared by means of
some dainty piece of mechanism; it is a very irregular tear. Somewhat
sharply, under the fierce heat of the sun, the satin bursts like the rind
of an over-ripe pomegranate. Judging by the result, we think of the
expansion of the air inside, which, heated by the sun, causes this
rupture. The signs of pressure from within are manifest: the tatters of
the torn fabric are turned outwards; also, a wisp of the russet eiderdown
that fills the wallet invariably straggles through the breach. In the
midst of the protruding floss, the Spiderlings, expelled from their home
by the explosion, are in frantic commotion.

The balloons of the Banded Epeira are bombs which, to free their
contents, burst under the rays of a torrid sun. To break they need the
fiery heat-waves of the dog-days. When kept in the moderate atmosphere
of my study, most of them do not open and the emergence of the young does
not take place, unless I myself I have a hand in the business; a few
others open with a round hole, a hole so neat that it might have been
made with a punch. This aperture is the work of the prisoners, who,
relieving one another in turns, have, with a patient tooth, bitten
through the stuff of the jar at some point or other.

When exposed to the full force of the sun, however, on the rosemaries in
the enclosure, the balloons burst and shoot forth a ruddy flood of floss
and tiny animals. That is how things occur in the free sun-bath of the
fields. Unsheltered, among the bushes, the wallet of the Banded Epeira,
when the July heat arrives, splits under the effort of the inner air. The
delivery is effected by an explosion of the dwelling.

A very small part of the family are expelled with the flow of tawny
floss; the vast majority remain in the bag, which is ripped open, but
still bulges with eiderdown. Now that the breach is made, any one can go
out who pleases, in his own good time, without hurrying. Besides, a
solemn action has to be performed before the emigration. The animal must
cast its skin; and the moult is an event that does not fall on the same
date for all. The evacuation of the place, therefore, lasts several
days. It is effected in small squads, as the slough is flung aside.

Those who sally forth climb up the neighbouring twigs and there, in the
full heat of the sun, proceed with the work of dissemination. The method
is the same as that which we saw in the case of the Cross Spider. The
spinnerets abandon to the breeze a thread that floats, breaks and flies
away, carrying the rope-maker with it. The number of starters on any one
morning is so small as to rob the spectacle of the greater part of its
interest. The scene lacks animation because of the absence of a crowd.

To my intense disappointment, the Silky Epeira does not either indulge in
a tumultuous and dashing exodus. Let me remind you of her handiwork, the
handsomest of the maternal wallets, next to the Banded Epeira's. It is
an obtuse conoid, closed with a star-shaped disk. It is made of a
stouter and especially a thicker material than the Banded Epeira's
balloon, for which reason a spontaneous rupture becomes more necessary
than ever.

This rupture is effected at the sides of the bag, not far from the edge
of the lid. Like the ripping of the balloon, it requires the rough aid
of the heat of July. Its mechanism also seems to work by the expansion
of the heated air, for we again see a partial emission of the silky floss
that fills the pouch.

The exit of the family is performed in a single group and, this time,
before the moult, perhaps for lack of the space necessary for the
delicate casting of the skin. The conical bag falls far short of the
balloon in size; those packed within would sprain their legs in
extracting them from their sheaths. The family, therefore, emerges in a
body and settles on a sprig hard by.

This is a temporary camping-ground, where, spinning in unison, the
youngsters soon weave an open-work tent, the abode of a week, or
thereabouts. The moult is effected in this lounge of intersecting
threads. The sloughed skins form a heap at the bottom of the dwelling;
on the trapezes above, the flaylings take exercise and gain strength and
vigour. Finally, when maturity is attained, they set out, now these, now
those, little by little and always cautiously. There are no audacious
flights on the thready airship; the journey is accomplished by modest
stages.

Hanging to her thread, the Spider lets herself drop straight down, to a
depth of nine or ten inches. A breath of air sets her swinging like a
pendulum, sometimes drives her against a neighbouring branch. This is a
step towards the dispersal. At the point reached, there is a fresh fall,
followed by a fresh pendulous swing that lands her a little farther
afield. Thus, in short tacks, for the thread is never very long, does
the Spiderling go about, seeing the country, until she comes to a place
that suits her. Should the wind blow at all hard, the voyage is cut
short: the cable of the pendulum breaks and the beastie is carried for
some distance on its cord.

To sum up, although, on the whole, the tactics of the exodus remain much
the same, the two spinstresses of my region best-versed in the art of
weaving mothers' wallets failed to come up to my expectations. I went to
the trouble of rearing them, with disappointing results. Where shall I
find again the wonderful spectacle which the Cross Spider offered me by
chance? I shall find it--in an even more striking fashion--among humbler
Spiders, whom I had neglected to observe.





Next: THE CRAB SPIDER

Previous: THE NARBONNE LYCOSA: THE CLIMBING-INSTINCT



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