Drover Dingdong's Sheep followed the Ram which Panurge had maliciously
thrown overboard and leapt nimbly into the sea, one after the other,
"for you know," says Rabelais, "it is the nature of the sheep always to
follow the first, wheresoever it goes."
The Pine caterpillar is even more sheeplike, not from foolishness, but
from necessity: where the first goes all the others go, in a regular
string, with not an empty space between them.
They proceed in single file, in a continuous row, each touching with
its head the rear of the one in front of it. The complex twists and
turns described in his vagaries by the caterpillar leading the van are
scrupulously described by all the others. No Greek theoria winding its
way to the Eleusinian festivals was ever more orderly. Hence the name
of Processionary given to the gnawer of the pine.
His character is complete when we add that he is a rope-dancer all his
life long: he walks only on the tight-rope, a silken rail placed in
position as he advances. The caterpillar who chances to be at the head
of the procession dribbles his thread without ceasing and fixes it on
the path which his fickle preferences cause him to take. The thread is
so tiny that the eye, though armed with a magnifying-glass, suspects it
rather than sees it.
But a second caterpillar steps on the slender foot-board and doubles it
with his thread; a third trebles it; and all the others, however many
there be, add the sticky spray from their spinnerets, so much so that,
when the procession has marched by, there remains, as a record of its
passing, a narrow white ribbon whose dazzling whiteness shimmers in the
sun. Very much more sumptuous than ours, their system of road-making
consists in upholstering with silk instead of macadamizing. We sprinkle
our roads with broken stones and level them by the pressure of a heavy
steam-roller; they lay over their paths a soft satin rail, a work of
general interest to which each contributes his thread.
What is the use of all this luxury? Could they not, like other
caterpillars, walk about without these costly preparations? I see two
reasons for their mode of progression. It is night when the
Processionaries sally forth to browse upon the pine-leaves. They leave
their nest, situated at the top of a bough, in profound darkness; they
go down the denuded pole till they come to the nearest branch that has
not yet been gnawed, a branch which becomes lower and lower by degrees
as the consumers finish stripping the upper storeys; they climb up this
untouched branch and spread over the green needles.
When they have had their suppers and begin to feel the keen night air,
the next thing is to return to the shelter of the house. Measured in a
straight line, the distance is not great, hardly an arm's length; but
it cannot be covered in this way on foot. The caterpillars have to
climb down from one crossing to the next, from the needle to the twig,
from the twig to the branch, from the branch to the bough and from the
bough, by a no less angular path, to go back home. It is useless to
rely upon sight as a guide on this long and erratic journey. The
Processionary, it is true, has five ocular specks on either side of his
head, but they are so infinitesimal, so difficult to make out through
the magnifying-glass, that we cannot attribute to them any great power
of vision. Besides, what good would those short-sighted lenses be in
the absence of light, in black darkness?
It is equally useless to think of the sense of smell. Has the
Processional any olfactory powers or has he not? I do not know. Without
giving a positive answer to the question, I can at least declare that
his sense of smell is exceedingly dull and in no way suited to help him
find his way. This is proved, in my experiments, by a number of hungry
caterpillars that, after a long fast, pass close beside a pine-branch
without betraying any eagerness of showing a sign of stopping. It is
the sense of touch that tells them where they are. So long as their
lips do not chance to light upon the pasture-land, not one of them
settles there, though he be ravenous. They do not hasten to food which
they have scented from afar; they stop at a branch which they encounter
on their way.
Apart from sight and smell, what remains to guide them in returning to
the nest? The ribbon spun on the road. In the Cretan labyrinth, Theseus
would have been lost but for the clue of thread with which Ariadne
supplied him. The spreading maze of the pine-needles is, especially at
night, as inextricable a labyrinth as that constructed for Minos. The
Processionary finds his way through it, without the possibility of a
mistake, by the aid of his bit of silk. At the time for going home,
each easily recovers either his own thread or one or other of the
neighbouring threads, spread fanwise by the diverging herd; one by one
the scattered tribe line up on the common ribbon, which started from
the nest; and the sated caravan finds its way back to the manor with
absolute certainty.
Longer expeditions are made in the daytime, even in winter, if the
weather be fine. Our caterpillars then come down from the tree, venture
on the ground, march in procession for a distance of thirty yards or
so. The object of these sallies is not to look for food, for the native
pine-tree is far from being exhausted: the shorn branches hardly count
amid the vast leafage. Moreover, the caterpillars observe complete
abstinence till nightfall. The trippers have no other object than a
constitutional, a pilgrimage to the outskirts to see what these are
like, possibly an inspection of the locality where, later on, they mean
to bury themselves in the sand for their metamorphosis.
It goes without saying that, in these greater evolutions, the guiding
cord is not neglected. It is now more necessary than ever. All
contribute to it from the produce of their spinnerets, as is the
invariable rule whenever there is a progression. Not one takes a step
forward without fixing to the path the thread from his lips.
If the series forming the procession be at all long, the ribbon is
dilated sufficiently to make it easy to find; nevertheless, on the
homeward journey, it is not picked up without some hesitation. For
observe that the caterpillars when on the march never turn completely;
to wheel round on their tight-rope is a method utterly unknown to them.
In order therefore to regain the road already covered, they have to
describe a zigzag whose windings and extent are determined by the
leader's fancy. Hence come gropings and roamings which are sometimes
prolonged to the point of causing the herd to spend the night out of
doors. It is not a serious matter. They collect into a motionless
cluster. To-morrow the search will start afresh and will sooner or
later be successful. Oftener still the winding curve meets the
guide-thread at the first attempt. As soon as the first caterpillar has
the rail between his legs, all hesitation ceases; and the band makes
for the nest with hurried steps.
The use of this silk-tapestried roadway is evident from a second point
of view. To protect himself against the severity of the winter which he
has to face when working, the Pine Caterpillar weaves himself a shelter
in which he spends his bad hours, his days of enforced idleness. Alone,
with none but the meagre resources of his silk-glands, he would find
difficulty in protecting himself on the top of a branch buffeted by the
winds. A substantial dwelling, proof against snow, gales and icy fogs,
requires the cooperation of a large number. Out of the individual's
piled-up atoms, the community obtains a spacious and durable
establishment.
The enterprise takes a long time to complete. Every evening, when the
weather permits, the building has to be strengthened and enlarged. It
is indispensable, therefore, that the corporation of workers should not
be dissolved while the stormy season continues and the insects are
still in the caterpillar stage. But, without special arrangements, each
nocturnal expedition at grazing-time would be a cause of separation. At
that moment of appetite for food there is a return to individualism.
The caterpillars become more or less scattered, settling singly on the
branches around; each browses his pine-needle separately. How are they
to find one another afterwards and become a community again?
The several threads left on the road make this easy. With that guide,
every caterpillar, however far he may be, comes back to his companions
without ever missing the way. They come hurrying from a host of twigs,
from here, from there, from above, from below; and soon the scattered
legion reforms into a group. The silk thread is something more than a
road-making expedient: it is the social bond, the system that keeps the
members of the brotherhood indissolubly united.
At the head of every procession, long or short, goes a first
caterpillar whom I will call the leader of the march or file, though
the word leader, which I use for the want of a better, is a little out
of place here. Nothing, in fact, distinguishes this caterpillar from
the others: it just depends upon the order in which they happen to line
up; and mere chance brings him to the front. Among the Processionaries,
every captain is an officer of fortune. The actual leader leads;
presently he will be a subaltern, if the line should break up in
consequence of some accident and be formed anew in a different order.
His temporary functions give him an attitude of his own. While the
others follow passively in a close file, he, the captain, tosses
himself about and with an abrupt movement flings the front of his body
hither and thither. As he marches ahead he seems to be seeking his way.
Does he in point of fact explore the country? Does he choose the most
practicable places? Or are his hesitations merely the result of the
absence of a guiding thread on ground that has not yet been covered?
His subordinates follow very placidly, reassured by the cord which they
hold between their legs; he, deprived of that support, is uneasy.
Why cannot I read what passes under his black, shiny skull, so like a
drop of tar to look at? To judge by actions, there is here a modicum of
discernment which is able, after experimenting, to recognize excessive
roughnesses, over-slippery surfaces, dusty places that offer no
resistance and, above all, the threads left by other excursionists.
This is all or nearly all that my long acquaintance with the
Processionaries has taught me as to their mentality. Poor brains,
indeed; poor creatures, whose commonwealth has its safety hanging upon
a thread!
The processions vary greatly in length. The finest that I have seen
manoeuvring on the ground measured twelve or thirteen yards and
numbered about three hundred caterpillars, drawn up with absolute
precision in a wavy line. But, if there were only two in a row the
order would still be perfect: the second touches and follows the first.
By February I have processions of all lengths in the greenhouse. What
tricks can I play upon them? I see only two: to do away with the
leader; and to cut the thread.
The suppression of the leader of the file produces nothing striking. If
the thing is done without creating a disturbance, the procession does
not alter its ways at all. The second caterpillar, promoted to captain,
knows the duties of his rank off-hand: he selects and leads, or rather
he hesitates and gropes.
The breaking of the silk ribbon is not very important either. I remove
a caterpillar from the middle of the file. With my scissors, so as not
to cause a commotion in the ranks, I cut the piece of ribbon on which
he stood and clear away every thread of it. As a result of this breach,
the procession acquires two marching leaders, each independent of the
other. It may be that the one in the rear joins the file ahead of him,
from which he is separated by but a slender interval; in that case,
things return to their original condition. More frequently, the two
parts do not become reunited. In that case, we have two distinct
processions, each of which wanders where it pleases and diverges from
the other. Nevertheless, both will be able to return to the nest by
discovering sooner or later, in the course of their peregrinations, the
ribbon on the other side of the break.
These two experiments are only moderately interesting. I have thought
out another, one more fertile in possibilities. I propose to make the
caterpillars describe a close circuit, after the ribbons running from
it and liable to bring about a change of direction have been destroyed.
The locomotive engine pursues its invariable course so long as it is
not shunted on to a branch-line. If the Processionaries find the silken
rail always clear in front of them, with no switches anywhere, will
they continue on the same track, will they persist in following a road
that never comes to an end? What we have to do is to produce this
circuit, which is unknown under ordinary conditions, by artificial
means.
The first idea that suggests itself is to seize with the forceps the
silk ribbon at the back of the train, to bend it without shaking it and
to bring the end of it ahead of the file. If the caterpillar marching
in the van steps upon it, the thing is done: the others will follow him
faithfully. The operation is very simple in theory but most difficult
in practice and produces no useful results. The ribbon, which is
extremely slight, breaks under the weight of the grains of sand that
stick to it and are lifted with it. If it does not break, the
caterpillars at the back, however delicately we may go to work, feel a
disturbance which makes them curl up or even let go.
There is a yet greater difficulty: the leader refuses the ribbon laid
before him; the cut end makes him distrustful. Failing to see the
regular, uninterrupted road, he slants off to the right or left, he
escapes at a tangent. If I try to interfere and to bring him back to
the path of my choosing, he persists in his refusal, shrivels up, does
not budge, and soon the whole procession is in confusion. We will not
insist: the method is a poor one, very wasteful of effort for at best a
problematical success.
We ought to interfere as little as possible and obtain a natural closed
circuit. Can it be done? Yes. It lies in our power, without the least
meddling, to see a procession march along a perfect circular track. I
owe this result, which is eminently deserving of our attention, to pure
chance.
On the shelf with the layer of sand in which the nests are planted
stand some big palm-vases measuring nearly a yard and a half in
circumference at the top. The caterpillars often scale the sides and
climb up to the moulding which forms a cornice around the opening. This
place suits them for their processions, perhaps because of the absolute
firmness of the surface, where there is no fear of landslides, as on
the loose, sandy soil below; and also, perhaps, because of the
horizontal position, which is favourable to repose after the fatigue of
the ascent. It provides me with a circular track all ready-made. I have
nothing to do but wait for an occasion propitious to my plans. This
occasion is not long in coming.
On the 30th of January, 1896, a little before twelve o'clock in the
day, I discover a numerous troop making their way up and gradually
reaching the popular cornice. Slowly, in single file, the caterpillars
climb the great vase, mount the ledge and advance in regular
procession, while others are constantly arriving and continuing the
series. I wait for the string to close up, that is to say, for the
leader, who keeps following the circular moulding, to return to the
point from which he started. My object is achieved in a quarter of an
hour. The closed circuit is realized magnificently, in something very
nearly approaching a circle.
The next thing is to get rid of the rest of the ascending column, which
would disturb the fine order of the procession by an excess of
newcomers; it is also important that we should do away with all the
silken paths, both new and old, that can put the cornice into
communication with the ground. With a thick hair-pencil I sweep away
the surplus climbers; with a big brush, one that leaves no smell behind
it--for this might afterwards prove confusing--I carefully rub down the
vase and get rid of every thread which the caterpillars have laid on
the march. When these preparations are finished, a curious sight awaits
us.
In the interrupted circular procession there is no longer a leader.
Each caterpillar is preceded by another on whose heels he follows
guided by the silk track, the work of the whole party; he again has a
companion close behind him, following him in the same orderly way. And
this is repeated without variation throughout the length of the chain.
None commands, or rather none modifies the trail according to his
fancy; all obey, trusting in the guide who ought normally to lead the
march and who in reality has been abolished by my trickery.
From the first circuit of the edge of the tub the rail of silk has been
laid in position and is soon turned into a narrow ribbon by the
procession, which never ceases dribbling its thread as it goes. The
rail is simply doubled and has no branches anywhere, for my brush has
destroyed them all. What will the caterpillars do on this deceptive,
closed path? Will they walk endlessly round and round until their
strength gives out entirely?
The old schoolmen were fond of quoting Buridan's Ass, that famous
Donkey who, when placed between two bundles of hay, starved to death
because he was unable to decide in favour of either by breaking the
equilibrium between two equal but opposite attractions. They slandered
the worthy animal. The Ass, who is no more foolish than any one else,
would reply to the logical snare by feasting off both bundles. Will my
caterpillars show a little of his mother wit? Will they, after many
attempts, be able to break the equilibrium of their closed circuit,
which keeps them on a road without a turning? Will they make up their
minds to swerve to this side or that, which is the only method of
reaching their bundle of hay, the green branch yonder, quite near, not
two feet off?
I thought that they would and I was wrong. I said to myself:
"The procession will go on turning for some time, for an hour, two
hours, perhaps; then the caterpillars will perceive their mistake. They
will abandon the deceptive road and make their descent somewhere or
other."
That they should remain up there, hard pressed by hunger and the lack
of cover, when nothing prevented them from going away, seemed to me
inconceivable imbecility. Facts, however, forced me to accept the
incredible. Let us describe them in detail.
The circular procession begins, as I have said, on the 30th of January,
about midday, in splendid weather. The caterpillars march at an even
pace, each touching the stern of the one in front of him. The unbroken
chain eliminates the leader with his changes of direction; and all
follow mechanically, as faithful to their circle as are the hands of a
watch. The headless file has no liberty left, no will; it has become
mere clockwork. And this continues for hours and hours. My success goes
far beyond my wildest suspicions. I stand amazed at it, or rather I am
stupefied.
Meanwhile, the multiplied circuits change the original rail into a
superb ribbon a twelfth of an inch broad. I can easily see it
glittering on the red ground of the pot. The day is drawing to a close
and no alteration has yet taken place in the position of the trail. A
striking proof confirms this.
The trajectory is not a plane curve, but one which, at a certain point,
deviates and goes down a little way to the lower surface of the
cornice, returning to the top some eight inches farther. I marked these
two points of deviation in pencil on the vase at the outset. Well, all
that afternoon and, more conclusive still, on the following days, right
to the end of this mad dance, I see the string of caterpillars dip
under the ledge at the first point and come to the top again at the
second. Once the first thread is laid, the road to be pursued is
permanently established.
If the road does not vary, the speed does. I measure nine centimetres
(3 1/2 inches.--Translator's Note.) a minute as the average distance
covered. But there are more or less lengthy halts; the pace slackens at
times, especially when the temperature falls. At ten o'clock in the
evening the walk is little more than a lazy swaying of the body. I
foresee an early halt, in consequence of the cold, of fatigue and
doubtless also of hunger.
Grazing-time has arrived. The caterpillars have come crowding from all
the nests in the greenhouse to browse upon the pine-branches planted by
myself beside the silken purses. Those in the garden do the same, for
the temperature is mild. The others, lined up along the earthenware
cornice, would gladly take part in the feast; they are bound to have an
appetite after a ten hours' walk. The branch stands green and tempting
not a hand's-breadth away. To reach it they need but go down; and the
poor wretches, foolish slaves of their ribbon that they are, cannot
make up their minds to do so. I leave the famished ones at half-past
ten, persuaded that they will take counsel with their pillow and that
on the morrow things will have resumed their ordinary course.
I was wrong. I was expecting too much of them when I accorded them that
faint gleam of intelligence which the tribulations of a distressful
stomach ought, one would think, to have aroused. I visit them at dawn.
They are lined up as on the day before, but motionless. When the air
grows a little warmer, they shake off their torpor, revive and start
walking again. The circular procession begins anew, like that which I
have already seen. There is nothing more and nothing less to be noted
in their machine-like obstinacy.
This time it is a bitter night. A cold snap has supervened, was indeed
foretold in the evening by the garden caterpillars, who refused to come
out despite appearances which to my duller senses seemed to promise a
continuation of the fine weather. At daybreak the rosemary-walks are
all asparkle with rime and for the second time this year there is a
sharp frost. The large pond in the garden is frozen over. What can the
caterpillars in the conservatory be doing? Let us go and see.
All are ensconced in their nests, except the stubborn processionists on
the edge of the vase, who, deprived of shelter as they are, seem to
have spent a very bad night. I find them clustered in two heaps,
without any attempt at order. They have suffered less from the cold,
thus huddled together.
'Tis an ill wind that blows nobody any good. The severity of the night
has caused the ring to break into two segments which will, perhaps,
afford a chance of safety. Each group, as it survives and resumes its
walk, will presently be headed by a leader who, not being obliged to
follow a caterpillar in front of him, will possess some liberty of
movement and perhaps be able to make the procession swerve to one side.
Remember that, in the ordinary processions, the caterpillar walking
ahead acts as a scout. While the others, if nothing occurs to create
excitement, keep to their ranks, he attends to his duties as a leader
and is continually turning his head to this side and that,
investigating, seeking, groping, making his choice. And things happen
as he decides: the band follows him faithfully. Remember also that,
even on a road which has already been travelled and beribboned, the
guiding caterpillar continues to explore.
There is reason to believe that the Processionaries who have lost their
way on the ledge will find a chance of safety here. Let us watch them.
On recovering from their torpor, the two groups line up by degrees into
two distinct files. There are therefore two leaders, free to go where
they please, independent of each other. Will they succeed in leaving
the enchanted circle? At the sight of their large black heads swaying
anxiously from side to side, I am inclined to think so for a moment.
But I am soon undeceived. As the ranks fill out, the two sections of
the chain meet and the circle is reconstituted. The momentary leaders
once more become simple subordinates; and again the caterpillars march
round and round all day.
For the second time in succession, the night, which is very calm and
magnificently starry, brings a hard frost. In the morning the
Processionaries on the tub, the only ones who have camped unsheltered,
are gathered into a heap which largely overflows both sides of the
fatal ribbon. I am present at the awakening of the numbed ones. The
first to take the road is, as luck will have it, outside the track.
Hesitatingly he ventures into unknown ground. He reaches the top of the
rim and descends upon the other side on the earth in the vase. He is
followed by six others, no more. Perhaps the rest of the troop, who
have not fully recovered from their nocturnal torpor, are too lazy to
bestir themselves.
The result of this brief delay is a return to the old track. The
caterpillars embark on the silken trail and the circular march is
resumed, this time in the form of a ring with a gap in it. There is no
attempt, however, to strike a new course on the part of the guide whom
this gap has placed at the head. A chance of stepping outside the magic
circle has presented itself at last; and he does not know how to avail
himself of it.
As for the caterpillars who have made their way to the inside of the
vase, their lot is hardly improved. They climb to the top of the palm,
starving and seeking for food. Finding nothing to eat that suits them,
they retrace their steps by following the thread which they have left
on the way, climb the ledge of the pot, strike the procession again
and, without further anxiety, slip back into the ranks. Once more the
ring is complete, once more the circle turns and turns.
Then when will the deliverance come? There is a legend that tells of
poor souls dragged along in an endless round until the hellish charm is
broken by a drop of holy water. What drop will good fortune sprinkle on
my Processionaries to dissolve their circle and bring them back to the
nest? I see only two means of conjuring the spell and obtaining a
release from the circuit. These two means are two painful ordeals. A
strange linking of cause and effect: from sorrow and wretchedness good
is to come.
And, first, shriveling as the result of cold, the caterpillars gather
together without any order, heap themselves some on the path, some,
more numerous these, outside it. Among the latter there may be, sooner
or later, some revolutionary who, scorning the beaten track, will trace
out a new road and lead the troop back home. We have just seen an
instance of it. Seven penetrated to the interior of the vase and
climbed the palm. True, it was an attempt with no result but still an
attempt. For complete success, all that need be done would have been to
take the opposite slope. An even chance is a great thing. Another time
we shall be more successful.
In the second place, the exhaustion due to fatigue and hunger. A lame
one stops, unable to go farther. In front of the defaulter the
procession still continues to wend its way for a short time. The ranks
close up and an empty space appears. On coming to himself and resuming
the march, the caterpillar who has caused the breach becomes a leader,
having nothing before him. The least desire for emancipation is all
that he wants to make him launch the band into a new path which perhaps
will be the saving path.
In short, when the Processionaries' train is in difficulties, what it
needs, unlike ours, is to run off the rails. The side-tracking is left
to the caprice of a leader who alone is capable of turning to the right
or left; and this leader is absolutely non-existent so long as the ring
remains unbroken. Lastly, the breaking of the circle, the one stroke of
luck, is the result of a chaotic halt, caused principally by excess of
fatigue or cold.
The liberating accident, especially that of fatigue, occurs fairly
often. In the course of the same day, the moving circumference is cut
up several times into two or three sections; but continuity soon
returns and no change takes place. Things go on just the same. The bold
innovator who is to save the situation has not yet had his inspiration.
There is nothing new on the fourth day, after an icy night like the
previous one; nothing to tell except the following detail. Yesterday I
did not remove the trace left by the few caterpillars who made their
way to the inside of the vase. This trace, together with a junction
connecting it with the circular road, is discovered in the course of
the morning. Half the troop takes advantage of it to visit the earth in
the pot and climb the palm; the other half remains on the ledge and
continues to walk along the old rail. In the afternoon the band of
emigrants rejoins the others, the circuit is completed and things
return to their original condition.
We come to the fifth day. The night frost becomes more intense, without
however as yet reaching the greenhouse. It is followed by bright
sunshine in a calm and limpid sky. As soon as the sun's rays have
warmed the panes a little, the caterpillars, lying in heaps, wake up
and resume their evolutions on the ledge of the vase. This time the
fine order of the beginning is disturbed and a certain disorder becomes
manifest, apparently an omen of deliverance near at hand. The
scouting-path inside the vase, which was upholstered in silk yesterday
and the day before, is to-day followed to its origin on the rim by a
part of the band and is then deserted after a short loop. The other
caterpillars follow the usual ribbon. The result of this bifurcation is
two almost equal files, walking along the ledge in the same direction,
at a short distance from each other, sometimes meeting, separating
farther on, in every case with some lack of order.
Weariness increases the confusion. The crippled, who refuse to go on,
are many. Breaches increase; files are split up into sections each of
which has its leader, who pokes the front of his body this way and that
to explore the ground. Everything seems to point to the disintegration
which will bring safety. My hopes are once more disappointed. Before
the night the single file is reconstituted and the invincible gyration
resumed.
Heat comes, just as suddenly as the cold did. To-day, the 4th of
February, is a beautiful, mild day. The greenhouse is full of life.
Numerous festoons of caterpillars, issuing from the nests, meander
along the sand on the shelf. Above them, at every moment, the ring on
the ledge of the vase breaks up and comes together again. For the first
time I see daring leaders who, drunk with heat, standing only on their
hinder prolegs at the extreme edge of the earthenware rim, fling
themselves forward into space, twisting about, sounding the depths. The
endeavour is frequently repeated, while the whole troop stops. The
caterpillars' heads give sudden jerks, their bodies wriggle.
One of the pioneers decides to take the plunge. He slips under the
ledge. Four follow him. The others, still confiding in the perfidious
silken path, dare not copy him and continue to go along the old road.
The short string detached from the general chain gropes about a great
deal, hesitates long on the side of the vase; it goes half-way down,
then climbs up again slantwise, rejoins and takes its place in the
procession. This time the attempt has failed, though at the foot of the
vase, not nine inches away, there lay a bunch of pine-needles which I
had placed there with the object of enticing the hungry ones. Smell and
sight told them nothing. Near as they were to the goal, they went up
again.
No matter, the endeavour has its uses. Threads were laid on the way and
will serve as a lure to further enterprise. The road of deliverance has
its first landmarks. And, two days later, on the eighth day of the
experiment, the caterpillars--now singly, anon in small groups, then
again in strings of some length--come down from the ledge by following
the staked-out path. At sunset the last of the laggards is back in the
nest.
Now for a little arithmetic. For seven times twenty-four hours the
caterpillars have remained on the ledge of the vase. To make an ample
allowance for stops due to the weariness of this one or that and above
all for the rest taken during the colder hours of the night, we will
deduct one-half of the time. This leaves eighty-four hours' walking.
The average pace is nine centimetres a minute. (3 1/2
inches.--Translator's Note.) The aggregate distance covered, therefore,
is 453 metres, a good deal more than a quarter of a mile, which is a
great walk for these little crawlers. The circumference of the vase,
the perimeter of the track, is exactly 1 metre 35. (4 feet 5
inches.--Translator's Note.) Therefore the circle covered, always in
the same direction and always without result, was described three
hundred and thirty-five times.
These figures surprise me, though I am already familiar with the
abysmal stupidity of insects as a class whenever the least accident
occurs. I feel inclined to ask myself whether the Processionaries were
not kept up there so long by the difficulties and dangers of the
descent rather than by the lack of any gleam of intelligence in their
benighted minds. The facts, however, reply that the descent is as easy
as the ascent.
The caterpillar has a very supple back, well adapted for twisting round
projections or slipping underneath. He can walk with the same ease
vertically or horizontally, with his back down or up. Besides, he never
moves forward until he has fixed his thread to the ground. With this
support to his feet, he has no falls to fear, no matter what his
position.
I had a proof of this before my eyes during a whole week. As I have
already said, the track, instead of keeping on one level, bends twice,
dips at a certain point under the ledge of the vase and reappears at
the top a little farther on. At one part of the circuit, therefore, the
procession walks on the lower surface of the rim; and this inverted
position implies so little discomfort or danger that it is renewed at
each turn for all the caterpillars from first to last.
It is out of the question then to suggest the dread of a false step on
the edge of the rim which is so nimbly turned at each point of
inflexion. The caterpillars in distress, starved, shelterless, chilled
with cold at night, cling obstinately to the silk ribbon covered
hundreds of times, because they lack the rudimentary glimmers of reason
which would advise them to abandon it.
Experience and reflection are not in their province. The ordeal of a
five hundred yards' march and three to four hundred turns teach them
nothing; and it takes casual circumstances to bring them back to the
nest. They would perish on their insidious ribbon if the disorder of
the nocturnal encampments and the halts due to fatigue did not cast a
few threads outside the circular path. Some three or four move along
these trails, laid without an object, stray a little way and, thanks to
their wanderings, prepare the descent, which is at last accomplished in
short strings favoured by chance.
The school most highly honoured to-day is very anxious to find the
origin of reason in the dregs of the animal kingdom. Let me call its
attention to the Pine Processionary.