My youthful meditations owe some happy moments to Condillac's famous
statue which, when endowed with the sense of smell, inhales the scent
of a rose and out of that single impression creates a whole world of
ideas. (Etienne Bonnot de Condillac, Abbé de Mureaux (1715-80), the
leading exponent of sensational philosophy. His most important work is
the "Traité des sensations," in which he imagines a statue, organized
like a man, and endows it with the senses one by one, beginning with
that of smell. He argues by a process of imaginative reconstruction
that all human faculties and all human knowledge are merely transformed
sensation, to the exclusion of any other principle, that, in short,
everything has its source in sensation: man is nothing but what he has
acquired.--Translator's Note.) My twenty-year-old mind, full of faith
in syllogisms, loved to follow the deductive jugglery of the
abbé-philosopher: I saw, or seemed to see, the statue take life in that
action of the nostrils, acquiring attention, memory, judgment and all
the psychological paraphernalia, even as still waters are aroused and
rippled by the impact of a grain of sand. I recovered from my illusion
under the instruction of my abler master, the animal. The Capricorn
shall teach us that the problem is more obscure than the abbé led me to
believe.
When wedge and mallet are at work, preparing my provision of firewood
under the grey sky that heralds winter, a favourite relaxation creates
a welcome break in my daily output of prose. By my express orders, the
woodman has selected the oldest and most ravaged trunks in his stack.
My tastes bring a smile to his lips; he wonders by what whimsy I prefer
wood that is worm-eaten--chirouna, as he calls it--to sound wood which
burns so much better. I have my views on the subject; and the worthy
man submits to them.
And now to us two, O my fine oak-trunk seamed with scars, gashed with
wounds whence trickle the brown drops smelling of the tan-yard. The
mallet drives home, the wedges bite, the wood splits. What do your
flanks contain? Real treasures for my studies. In the dry and hollow
parts, groups of various insects, capable of living through the bad
season of the year, have taken up their winter quarters: in the
low-roofed galleries, galleries which some Buprestis-beetle has built,
Osmia-bees, working their paste of masticated leaves, have piled their
cells, one above the other; in the deserted chambers and vestibules,
Megachiles (Leaf-cutting Bees.--Translator's Note.) have arranged their
leafy jars; in the live wood, filled with juicy saps, the larvae of the
Capricorn (Cerambyx miles), the chief author of the oak's undoing, have
set up their home.
Strange creatures, of a verity, are these grubs, for an insect of
superior organization: bits of intestines crawling about! At this time
of year, the middle of autumn, I meet them of two different ages. The
older are almost as thick as one's finger; the others hardly attain the
diameter of a pencil. I find, in addition, pupae more or less fully
coloured, perfect insects, with a distended abdomen, ready to leave the
trunk when the hot weather comes again. Life inside the wood,
therefore, lasts three years. How is this long period of solitude and
captivity spent? In wandering lazily through the thickness of the oak,
in making roads whose rubbish serves as food. The horse in Job swallows
the ground in a figure of speech; the Capricorn's grub literally eats
its way. ("Chafing and raging, he swalloweth the ground, neither doth
he make account when the noise of the trumpet soundeth."--Job 39, 23
(Douai version).--Translator's Note.) With its carpenter's gouge, a
strong black mandible, short, devoid of notches, scooped into a
sharp-edged spoon, it digs the opening of its tunnel. The piece cut out
is a mouthful which, as it enters the stomach, yields its scanty juices
and accumulates behind the worker in heaps of wormed wood. The refuse
leaves room in front by passing through the worker. A labour at once of
nutrition and of road-making, the path is devoured while constructed;
it is blocked behind as it makes way ahead. That, however, is how all
the borers who look to wood for victuals and lodging set about their
business.
For the harsh work of its two gouges, or curved chisels, the larva of
the Capricorn concentrates its muscular strength in the front of its
body, which swells into a pestle-head. The Buprestis-grubs, those other
industrious carpenters, adopt a similar form; they even exaggerate
their pestle. The part that toils and carves hard wood requires a
robust structure; the rest of the body, which has but to follow after,
continues slim. The essential thing is that the implement of the jaws
should possess a solid support and a powerful motor. The Cerambyx-larva
strengthens its chisels with a stout, black, horny armour that
surrounds the mouth; yet, apart from its skull and its equipment of
tools, the grub has a skin as fine as satin and white as ivory. This
dead white comes from a copious layer of grease which the animal's
spare diet would not lead us to suspect. True, it has nothing to do, at
every hour of the day and night, but gnaw. The quantity of wood that
passes into its stomach makes up for the dearth of nourishing elements.
The legs, consisting of three pieces, the first globular, the last
sharp-pointed, are mere rudiments, vestiges. They are hardly a
millimetre long. (.039 inch.--Translator's Note.) For this reason they
are of no use whatever for walking; they do not even bear upon the
supporting surface, being kept off it by the obesity of the chest. The
organs of locomotion are something altogether different. The grub of
the Capricorn moves at the same time on its back and belly; instead of
the useless legs of the thorax, it has a walking-apparatus almost
resembling feet, which appear, contrary to every rule, on the dorsal
surface.
The first seven segments of the abdomen have, both above and below, a
four-sided facet, bristling with rough protuberances. This the grub can
either expand or contract, making it stick out or lie flat at will. The
upper facets consist of two excrescences separated by the mid-dorsal
line; the lower ones have not this divided appearance. These are the
organs of locomotion, the ambulacra. When the larva wishes to move
forwards, it expands its hinder ambulacra, those on the back as well as
those on the belly, and contracts its front ones. Fixed to the side of
the narrow gallery by their ridges, the hind-pads give the grub a
purchase. The flattening of the fore-pads, by decreasing the diameter,
allows it to slip forward and to take half a step. To complete the step
the hind-quarters have to be brought up the same distance. With this
object, the front pads fill out and provide support, while those behind
shrink and leave free scope for their segments to contract.
With the double support of its back and belly, with alternate puffings
and shrinkings, the animal easily advances or retreats along its
gallery, a sort of mould which the contents fill without a gap. But if
the locomotory pads grip only on one side progress becomes impossible.
When placed on the smooth wood of my table, the animal wriggles slowly;
it lengthens and shortens without advancing by a hair's-breadth. Laid
on the surface of a piece of split oak, a rough, uneven surface, due to
the gash made by the wedge, it twists and writhes, moves the front part
of its body very slowly from left to right and right to left, lifts it
a little, lowers it and begins again. These are the most extensive
movements made. The vestigial legs remain inert and absolutely useless.
Then why are they there? It were better to lose them altogether, if it
be true that crawling inside the oak has deprived the animal of the
good legs with which it started. The influence of environment, so
well-inspired in endowing the grub with ambulatory pads, becomes a
mockery when it leaves it these ridiculous stumps. Can the structure,
perchance, be obeying other rules than those of environment?
Though the useless legs, the germs of the future limbs, persist, there
is no sign in the grub of the eyes wherewith the Cerambyx will be
richly gifted. The larva has not the least trace of organs of vision.
What would it do with sight in the murky thickness of a tree-trunk?
Hearing is likewise absent. In the never-troubled silence of the oak's
inmost heart, the sense of hearing would be a non-sense. Where sounds
are lacking, of what use is the faculty of discerning them? Should
there be any doubts, I will reply to them with the following
experiment. Split lengthwise, the grub's abode leaves a half-tunnel
wherein I can watch the occupant's doings. When left alone, it now
gnaws the front of its gallery, now rests, fixed by its ambulacra to
the two sides of the channel. I avail myself of these moments of quiet
to inquire into its power of perceiving sounds. The banging of hard
bodies, the ring of metallic objects, the grating of a file upon a saw
are tried in vain. The animal remains impassive. Not a wince, not a
movement of the skin; no sign of awakened attention. I succeed no
better when I scratch the wood close by with a hard point, to imitate
the sound of some neighbouring larva gnawing the intervening thickness.
The indifference to my noisy tricks could be no greater in a lifeless
object. The animal is deaf.
Can it smell? Everything tells us no. Scent is of assistance in the
search for food. But the Capricorn grub need not go in quest of
eatables: it feeds on its home, it lives on the wood that gives it
shelter. Let us make an attempt or two, however. I scoop in a log of
fresh cypress-wood a groove of the same diameter as that of the natural
galleries and I place the worm inside it. Cypress-wood is strongly
scented; it possesses in a high degree that resinous aroma which
characterizes most of the pine family. Well, when laid in the
odoriferous channel, the larva goes to the end, as far as it can go,
and makes no further movement. Does not this placid quiescence point to
the absence of a sense of smell? The resinous flavour, so strange to
the grub which has always lived in oak, ought to vex it, to trouble it;
and the disagreeable impression ought to be revealed by a certain
commotion, by certain attempts to get away. Well, nothing of the kind
happens: once the larva has found the right position in the groove, it
does not stir. I do more: I set before it, at a very short distance, in
its normal canal, a piece of camphor. Again, no effect. Camphor is
followed by naphthaline. Still nothing. After these fruitless
endeavours, I do not think that I am going too far when I deny the
creature a sense of smell.
Taste is there, no doubt. But such taste! The food is without variety:
oak, for three years at a stretch, and nothing else. What can the
grub's palate appreciate in this monotonous fare? The tannic relish of
a fresh piece, oozing with sap, the uninteresting flavour of an
over-dry piece, robbed of its natural condiment: these probably
represent the whole gustative scale.
There remains touch, the far-spreading, passive sense common to all
live flesh that quivers under the goad of pain. The sensitive schedule
of the Cerambyx-grub, therefore, is limited to taste and touch, both
exceedingly obtuse. This almost brings us to Condillac's statue. The
imaginary being of the philosopher had one sense only, that of smell,
equal in delicacy to our own; the real being, the ravager of the oak,
has two, inferior, even when put together, to the former, which so
plainly perceived the scent of a rose and distinguished it so clearly
from any other. The real case will bear comparison with the fictitious.
What can be the psychology of a creature possessing such a powerful
digestive organism combined with such a feeble set of senses? A vain
wish has often come to me in my dreams; it is to be able to think, for
a few minutes, with the crude brain of my Dog, to see the world with
the faceted eyes of a Gnat. How things would change in appearance! They
would change much more if interpreted by the intellect of the grub.
What have the lessons of touch and taste contributed to that
rudimentary receptacle of impressions? Very little; almost nothing. The
animal knows that the best bits possess an astringent flavour; that the
sides of a passage not carefully planed are painful to the skin. This
is the utmost limit of its acquired wisdom. In comparison, the statue
with the sensitive nostrils was a marvel of knowledge, a paragon too
generously endowed by its inventor. It remembered, compared, judged,
reasoned: does the drowsily digesting paunch remember? Does it compare?
Does it reason? I defined the Capricorn-grub as a bit of an intestine
that crawls about. The undeniable accuracy of this definition provides
me with my answer: the grub has the aggregate of sense-impressions that
a bit of an intestine may hope to have.
And this nothing-at-all is capable of marvellous acts of foresight;
this belly, which knows hardly aught of the present, sees very clearly
into the future. Let us take an illustration on this curious subject.
For three years on end the larva wanders about in the thick of the
trunk; it goes up, goes down, turns to this side and that; it leaves
one vein for another of better flavour, but without moving too far from
the inner depths, where the temperature is milder and greater safety
reigns. A day is at hand, a dangerous day for the recluse obliged to
quit its excellent retreat and face the perils of the surface. Eating
is not everything: we have to get out of this. The larva, so
well-equipped with tools and muscular strength, finds no difficulty in
going where it pleases, by boring through the wood; but does the coming
Capricorn, whose short spell of life must be spent in the open air,
possess the same advantages? Hatched inside the trunk, will the
long-horned insect be able to clear itself a way of escape?
That is the difficulty which the worm solves by inspiration. Less
versed in things of the future, despite my gleams of reason, I resort
to experiment with a view to fathoming the question. I begin by
ascertaining that the Capricorn, when he wishes to leave the trunk, is
absolutely unable to make use of the tunnel wrought by the larva. It is
a very long and very irregular maze, blocked with great heaps of wormed
wood. Its diameter decreases progressively from the final blind alley
to the starting-point. The larva entered the timber as slim as a tiny
bit of straw; it is to-day as thick as my finger. In its three years'
wanderings it always dug its gallery according to the mould of its
body. Evidently, the road by which the larva entered and moved about
cannot be the Capricorn's exit-way: his immoderate antennae, his long
legs, his inflexible armour-plates would encounter an insuperable
obstacle in the narrow, winding corridor, which would have to be
cleared of its wormed wood and, moreover, greatly enlarged. It would be
less fatiguing to attack the untouched timber and dig straight ahead.
Is the insect capable of doing so? We shall see.
I make some chambers of suitable size in oak logs chopped in two; and
each of my artificial cells receives a newly transformed Cerambyx, such
as my provisions of firewood supply, when split by the wedge, in
October. The two pieces are then joined and kept together with a few
bands of wire. June comes. I hear a scraping inside my billets. Will
the Capricorns come out, or not? The delivery does not seem difficult
to me: there is hardly three-quarters of an inch to pierce. Not one
emerges. When all is silence, I open my apparatus. The captives, from
first to last, are dead. A vestige of sawdust, less than a pinch of
snuff, represents all their work.
I expected more from those sturdy tools, their mandibles. But, as I
have said elsewhere, the tool does not make the workman. In spite of
their boring-implements, the hermits die in my cases for lack of skill.
I subject others to less arduous tests. I enclose them in spacious
reed-stumps, equal in diameter to the natal cell. The obstacle to be
pierced is the natural diaphragm, a yielding partition two or three
millimetres thick. (.078 to .117 inch.--Translator's Note.) Some free
themselves; others cannot. The less vibrant ones succumb, stopped by
the frail barrier. What would it be if they had to pass through a
thickness of oak?
We are now persuaded: despite his stalwart appearance, the Capricorn is
powerless to leave the tree-trunk by his unaided efforts. It therefore
falls to the worm, to the wisdom of that bit of an intestine, to
prepare the way for him. We see renewed, in another form, the feats of
prowess of the Anthrax, whose pupa, armed with trepans, bores through
rock on the feeble Fly's behalf. Urged by a presentiment that to us
remains an unfathomable mystery, the Cerambyx-grub leaves the inside of
the oak, its peaceful retreat, its unassailable stronghold, to wriggle
towards the outside, where lives the foe, the Woodpecker, who may
gobble up the succulent little sausage. At the risk of its life, it
stubbornly digs and gnaws to the very bark, of which it leaves no more
intact than the thinnest film, a slender screen. Sometimes, even, the
rash one opens the window wide.
This is the Capricorn's exit-hole. The insect will have but to file the
screen a little with its mandibles, to bump against it with its
forehead, in order to bring it down; it will even have nothing to do
when the window is free, as often happens. The unskilled carpenter,
burdened with his extravagant head-dress, will emerge from the darkness
through this opening when the summer heats arrive.
After the cares of the future come the cares of the present. The larva,
which has just opened the aperture of escape, retreats some distance
down its gallery and, in the side of the exit-way, digs itself a
transformation-chamber more sumptuously furnished and barricaded than
any that I have ever seen. It is a roomy niche, shaped like a flattened
ellipsoid, the length of which reaches eighty to a hundred millimetres.
(3 to 4 inches.--Translator's Note.) The two axes of the cross-section
vary: the horizontal measures twenty-five to thirty millimetres (.975
to 1.17 inch.--Translator's Note.); the vertical measures only fifteen.
(.585 inch.--Translator's Note.) This greater dimension of the cell,
where the thickness of the perfect insect is concerned, leaves a
certain scope for the action of its legs when the time comes for
forcing the barricade, which is more than a close-fitting mummy-case
would do.
The barricade in question, a door which the larva builds to exclude the
dangers from without, is two-and even three-fold. Outside, it is a
stack of woody refuse, of particles of chopped timber; inside, a
mineral hatch, a concave cover, all in one piece, of a chalky white.
Pretty often, but not always, there is added to these two layers an
inner casing of shavings. Behind this compound door, the larva makes
its arrangements for the metamorphosis. The sides of the chamber are
rasped, thus providing a sort of down formed of ravelled woody fibres,
broken into minute shreds. The velvety matter, as and when obtained, is
applied to the wall in a continuous felt at least a millimetre thick.
(.039 inch.--Translator's Note.) The chamber is thus padded throughout
with a fine swan's-down, a delicate precaution taken by the rough worm
on behalf of the tender pupa.
Let us hark back to the most curious part of the furnishing, the
mineral hatch or inner door of the entrance. It is an elliptical
skull-cap, white and hard as chalk, smooth within and knotted without,
resembling more or less closely an acorn-cup. The knots show that the
matter is supplied in small, pasty mouthfuls, solidifying outside in
slight projections which the insect does not remove, being unable to
get at them, and polished on the inside surface, which is within the
worm's reach. What can be the nature of that singular lid whereof the
Cerambyx furnishes me with the first specimen? It is as hard and
brittle as a flake of lime-stone. It can be dissolved cold in nitric
acid, discharging little gaseous bubbles. The process of solution is a
slow one, requiring several hours for a tiny fragment. Everything is
dissolved, except a few yellowish flocks, which appear to be of an
organic nature. As a matter of fact, a piece of the hatch, when
subjected to heat, blackens, proving the presence of an organic glue
cementing the mineral matter. The solution becomes muddy if oxalate of
ammonia be added; it then deposits a copious white precipitate. These
signs indicate calcium carbonate. I look for urate of ammonia, that
constantly recurring product of the various stages of the
metamorphoses. It is not there: I find not the least trace of murexide.
The lid, therefore, is composed solely of carbonate of lime and of an
organic cement, no doubt of an albuminous character, which gives
consistency to the chalky paste.
Had circumstances served me better, I should have tried to discover in
which of the worm's organs the stony deposit dwells. I am however,
convinced: it is the stomach, the chylific ventricle, that supplies the
chalk. It keeps it separated from the food, either as original matter
or as a derivative of the ammonium urate; it purges it of all foreign
bodies, when the larval period comes to an end, and holds it in reserve
until the time comes to disgorge it. This freestone factory causes me
no astonishment: when the manufacturer undergoes his change, it serves
for various chemical works. Certain Oil-beetles, such as the Sitaris,
locate in it the urate of ammonia, the refuse of the transformed
organism; the Sphex, the Pelopaei, the Scoliae use it to manufacture
the shellac wherewith the silk of the cocoon is varnished. Further
investigations will only swell the aggregate of the products of this
obliging organ.
When the exit-way is prepared and the cell upholstered in velvet and
closed with a threefold barricade, the industrious worm has concluded
its task. It lays aside its tools, sheds its skin and becomes a nymph,
a pupa, weakness personified, in swaddling-clothes, on a soft couch.
The head is always turned towards the door. This is a trifling detail
in appearance; but it is everything in reality. To lie this way or that
in the long cell is a matter of great indifference to the grub, which
is very supple, turning easily in its narrow lodging and adopting
whatever position it pleases. The coming Capricorn will not enjoy the
same privileges. Stiffly girt in his horn cuirass, he will not be able
to turn from end to end; he will not even be capable of bending, if
some sudden wind should make the passage difficult. He must absolutely
find the door in front of him, lest he perish in the casket. Should the
grub forget this little formality, should it lie down to its nymphal
sleep with its head at the back of the cell, the Capricorn is
infallibly lost: his cradle becomes a hopeless dungeon.
But there is no fear of this danger: the knowledge of our bit of an
intestine is too sound in things of the future for the grub to neglect
the formality of keeping its head to the door. At the end of spring,
the Capricorn, now in possession of his full strength, dreams of the
joys of the sun, of the festivals of light. He wants to get out. What
does he find before him? A heap of filings easily dispersed with his
claws; next, a stone lid which he need not even break into fragments:
it comes undone in one piece; it is removed from its frame with a few
pushes of the forehead, a few tugs of the claws. In fact, I find the
lid intact on the threshold of the abandoned cells. Last comes a second
mass of woody remnants, as easy to disperse as the first. The road is
now free: the Cerambyx has but to follow the spacious vestibule, which
will lead him, without the possibility of mistake, to the exit. Should
the window not be open, all that he has to do is to gnaw through a thin
screen: an easy task; and behold him outside, his long antennae aquiver
with excitement.
What have we learnt from him? Nothing, from him; much from his grub.
This grub, so poor in sensory organs, gives us no little food for
reflection with its prescience. It knows that the coming Beetle will
not be able to cut himself a road through the oak and it bethinks
itself of opening one for him at its own risk and peril. It knows that
the Cerambyx, in his stiff armour, will never be able to turn and make
for the orifice of the cell; and it takes care to fall into its nymphal
sleep with its head to the door. It knows how soft the pupa's flesh
will be and upholsters the bedroom with velvet. It knows that the enemy
is likely to break in during the slow work of the transformation and,
to set a bulwark against his attacks, it stores a calcium pap inside
its stomach. It knows the future with a clear vision, or, to be
accurate, behaves as though it knew it. Whence did it derive the
motives of its actions? Certainly not from the experience of the
senses. What does it know of the outside world? Let us repeat, as much
as a bit of an intestine can know. And this senseless creature fills us
with amazement! I regret that the clever logician, instead of
conceiving a statue smelling a rose, did not imagine it gifted with
some instinct. How quickly he would have recognized that, quite apart
from sense-impressions, the animal, including man, possesses certain
psychological resources, certain inspirations that are innate and not
acquired!