ABERRATIONS OF INSTINCT
So far as the Pelopæus is concerned, my part as an observer is
concluded, a part of no great interest, I am the first to admit, if we
limit its scope merely to the data which it is able to supply. That the
insect frequents our dwellings, that it builds a mud nest victualled
with Spiders, that it weaves itself a bag which looks as it it were cut
out of an onion-skin: all these details matter to us but little. They
may please the collector who zealously sets down everything, down to
the nervation of a wing, in order to throw a little light on his
systematic arrangements; but the mind nourished with more serious ideas
sees nothing in all this but the food of an almost puerile curiosity.
Is it really worth while to spend our time, the time which escapes us
so swiftly, this stuff of life, as Montaigne calls it, in gleaning
facts of indifferent moment and of highly contestable utility? Is it
not childish to enquire so minutely into an insect’s actions? Too many
interests of a graver kind hold us in their grasp to leave us any
leisure for these amusements. That is how the harsh experience of age
impels us to speak; that is how I should conclude, as I bring my
investigations to a close, if I did not perceive, amid the chaos of my
observations, a few gleams of light touching the loftiest problems
which we are privileged to discuss.
What is life? Will it ever be possible for us to trace it to its
sources? Shall we ever be permitted to excite, in a drop of albumen,
the uncertain quiverings which are the preludes of organization? What
is human intelligence? In what respect does it differ from animal
intelligence? What is instinct? Are these two mental aptitudes
irreducible, or can they both be traced back to a common factor? Are
the species connected with one another, are they related by evolution?
Or are they, as it were, so many unchangeable medals, each struck from
a separate die upon which the tooth of time has no effect, except to
destroy it sooner or later? These questions are and always will be the
despair of every cultivated mind, even though the inanity of our
efforts to solve them urges us to cast them into the limbo of the
unknowable. The theorists, proudly daring, have an answer nowadays for
every question; but, as a thousand theoretical views are not worth a
single fact, thinkers untrammelled by preconceived ideas are far from
being convinced. Problems such as these, whether their scientific
solution be possible or not, require an enormous mass of
well-established data, to which entomology, despite its humble
province, can contribute a quota of some value. And that is why I am an
observer, why, above all, I am an experimenter.
It is something to observe; but it is not enough: we must experiment,
that is to say, we must ourselves intervene and create artificial
conditions which oblige the animal to reveal to us what it would not
tell if left to the normal course of events. Its actions, marvellously
contrived to attain the end pursued, are capable of deceiving us as to
their real meaning and of making us accept, in their linked sequence,
that which our own logic dictates to us. It is not the animal that we
are now consulting upon the nature of its aptitudes, upon the primary
motives of its activity, but our own opinions, which always yield a
reply in favour of our cherished notions. As I have already repeatedly
shown, observation in itself is often a snare: we interpret its data
according to the exigencies of our theories. To bring out the truth, we
must needs resort to experiment, which alone is able to some extent to
fathom the obscure problem of animal intelligence. It has sometimes
been denied that zoology is an experimental science. The accusation
would be well-founded if zoology confined itself to describing and
classifying; but this is the least important part of its function: it
has higher aims than that; and, when it consults the animal upon some
problem of life, its method of questioning lies in experiment. In my
own modest sphere, I should be depriving myself of the most potent
method of study if I were to neglect experiment. Observation sets the
problem; experiment solves it, always presuming that it can be solved;
or at least, if powerless to yield the full light of truth, it sheds a
certain gleam over the edges of the impenetrable cloud.
Let us return to the Pelopæus, to whom it is time to apply the
experimental method. A cell has recently been completed. The huntress
arrives with her first Spider. She stores it away and at once fastens
her egg upon the Spider’s belly. She sets out on a second trip. I take
advantage of her absence to remove with my tweezers from the bottom of
the cell the head of game and the egg. What will the insect do on its
return, confronted with this empty cell, this cell no longer containing
the egg, the sole object of her industry as a potter and her skill as a
huntress?
The disappearance of the egg must be obvious to the Wasp who has been
robbed of it, if her poor intelligence possess so much as the
rudimentary gleam that enables us to distinguish between a thing’s
presence and its absence. The egg, were it alone, being of small
dimensions, might escape the mother’s vigilance; but it lies upon a
comparatively bulky Spider, of whose presence the Pelopæus, on
returning to the nest, is undoubtedly apprised by her sense of touch
and sight when she deposits the second victim beside the first. If this
big object be missing, the egg is missing likewise, so the most
elementary trace of reason that it is possible to conceive ought to
tell her. Once more, what will the Pelopæus do when confronted with her
cell, where the absence of the egg henceforth renders the bringing of
provisions useless and absurd, unless and until she repairs the loss by
laying a second egg? She will do precisely what we have already seen in
the Mason-bee of the Sheds, but under less striking conditions: she
will act absurdly and wear herself out uselessly.
What she does is to bring a second Spider, whom she stores away with
the same cheerful zeal as though nothing untoward had occurred; she
brings a third, a fourth and others still, each of whom I remove during
her absence, so that every time that she returns from the chase the
warehouse is found empty. For two days the Pelopæus’ obstinacy in
seeking to fill the insatiable jar persisted; for two days my patience
in emptying the pot as she stocked it was equally unflagging. With the
twentieth victim, persuaded, perhaps, by the fatigue of expeditions
repeated beyond all measure, the huntress considered that the game-bag
was sufficiently supplied; and she began most conscientiously to close
the cell which contained absolutely nothing.
The Mason-bees whose cups I used to empty as and when they brushed off
the pollen-dust and disgorged the honey-paste gave proof of similar
inconsistencies: I would see them laying the egg in the empty cell and
then closing the cell as though the provisions were still there. One
point alone used to cause me some anxiety; my plug of cotton-wool left
behind it, on the wall against which it rubbed, a smear of honey whose
smell might deceive the insect by concealing the absence of the
victuals. The coarser sense of touch was dumb while the finer sense of
smell continued to speak. In the case of the famous statue of which
Condillac [44] tells us, the sole stimulant of mental activity was the
scent of a rose. The insect’s intelligence is certainly very
differently equipped; nevertheless we may ask ourselves whether, in a
Bee, the scent of the honey would not be so far predominant as to cheat
other impressions. This, at all events, would explain the laying of the
egg in a cell containing no provisions, but still full of their good
smell; it would explain the scrupulous sealing of the cell in which the
larva is doomed to die of starvation.
To avoid those foolish objections, the last resource of an opponent at
bay, I should therefore like something better than the absurd action of
the Mason-bees. And this the Pelopæus has just given us. Here we have
no fragrant smear left behind by the victuals withdrawn, no vestige
than can conceal the absence of provisions from the mother. The Spider
whom my tweezers are about to seize at the bottom of the cell leaves no
trace of her temporary sojourn, nor does the egg extracted with the
first morsel, so that the Wasp cannot fail to be apprised of the void
created in her cell, if she be capable of being apprised of anything.
It makes no difference; nothing alters her habitual course of action.
During two days, she brings a score of items, one by one, as each
preceding item is removed; the stubborn hunt is prolonged, on behalf of
an egg which has been absent from the outset; and at length the door of
the cell is closed with the same care as under normal conditions.
Before considering the inferences to be drawn from this odd behaviour,
we will record an even more striking experiment, also made at the
Pelopæus’ expense. I have described how, when the group of cells is
completed, the insect plasters its nest, covering it with a thick rind
of mud under which all the elegance of the pottery disappears. I
surprise a Pelopæus at the moment when she is spreading her first
pellets to form an outer casing. The nest is fastened to a wall coated
with mortar. The idea occurs to me to take it away, in the vague hope
of beholding something new. And something new there is, nay more,
something so absurd that one would never have dared to foresee it. Let
me begin by explaining that naught remains of the nest, when I have
removed it and put it in my pocket, except a thin, broken line, marking
the circumference of the clod of mud. Within this ring, save for a few
fragments of mud, the wall has resumed the whiteness of its coat of
mortar, a very different colour from that of the nest, which is an
ashen grey.
The Pelopæus arrives with her load of clay. Without any hesitation that
I can perceive, she alights on the deserted spot and deposits her
pellet there, spreading it slightly. The operation would have been
conducted no differently on the nest itself. Judging by the quiet and
zealous way in which the Wasp is working, there is no doubt but that
she really believes herself to be plastering her house, whereas she is
merely plastering its uncovered support. The new colour of the site and
its flat surface, replacing the prominence of the vanished clod, fail
to apprise her that the nest is gone.
Can this be a temporary distraction, a blunder due to the Wasp’s
excessive eagerness for work? She will change her mind, no doubt,
perceive her mistake and discontinue her futile labours. But no: I see
her coming back thirty times in succession. At each trip she brings a
globule of mud, which she applies, without making a single error,
inside the circumference formed by the line of clay which the base of
the nest has left on the wall. Her memory, which tells her nothing of
the colour, shape or prominence of the nest, is surprisingly faithful
in matters of topographical detail: it knows nothing of essentials but
is thoroughly acquainted with accessories; topographically speaking,
the nest is there; the structure, it is true, is missing, but there is
the supporting base; and that, it appears, is enough; at any rate, the
Pelopæus is lavish of her exertions in bringing mud to plaster the
surface on which the structure no longer stands.
In the old days, the Mason-bees used to surprise me greatly with their
tenacious memory of the spot where the pebble lay supporting their nest
and with their lack of perspicacity in all that concerned the nest
itself, which was replaced by another, quite different nest without
making them interrupt the work already begun. The Pelopæus outdoes them
in these aberrations: she gives the last strokes of the trowel to an
imaginary dwelling, of which nothing but the site remains.
Has she, as a matter of fact, a more obtuse intellect than the
dome-builder? The entomological tribe seems hardly to swerve from a
common stock of aptitudes; those whom we consider the most richly
endowed, on the evidence of actions normally accomplished, show
themselves as limited as the rest when the experimenter disturbs the
current of their instincts. It is probable that the Mason-bee would
have committed the same absurdities as the Pelopæus, had I thought of
subjecting her, at a propitious time, to a similar test. A plasterer by
profession, she would, like the other, have plastered the base of the
nest removed from the pebble at the right moment. My confidence in the
glimmer of reason which the makers of theories attribute to the animal
is so greatly shaken that I do not regard my unflattering opinion of
the Mason-bee as rash.
Thirty times, I said, in my presence did the artist in earthenware lay
and then spread her pellet of mud upon the bare wall, thinking that she
was applying it to the nest itself. Sufficiently informed by this long
perseverance, I left the Pelopæus still busy at her futile task. Two
days later, I inspected the plastered site. The coating of mud did not
differ from that shown by a finished nest.
I have suggested that the insect’s rudimentary intelligence has
practically the same limitations everywhere. The accidental difficulty
which one insect is powerless to overcome, in default of a gleam of
judgment, any other, no matter what its genus or species, will be
equally unable to overcome. To vary the evidence, I will borrow my next
example from the Lepidoptera. [45]
The Great Peacock [46] is the largest Moth of our district. Her
caterpillar, which is yellow-hued, with turquoise-blue spots surrounded
by black hairs, spins itself, at the foot of the almond-trees, a robust
cocoon whose ingenious construction has long been celebrated. At the
moment of her deliverance, the Mulberry Bombyx [47] has in her stomach
a particular solvent which the new-born Moth disgorges against the wall
of the cocoon to soften it, to dissolve the gum that sticks the threads
together and in this way to force an exit by the mere pressure of her
head. With the aid of this reagent, the recluse is able triumphantly to
attack her silken prison at the fore-end, the rear-end or the side, as
I discover by turning the chrysalis in its cocoon, which I slit with a
pair of scissors and then sew up again. Whatever the spot to be
perforated for the emergence, a spot which my intervention varies at
will, the liquid disgorged promptly soaks into and softens the wall,
whereupon the captive, struggling with her fore-limbs and pushing her
forehead against the tangle of unstuck threads, makes herself a passage
with the same ease as in her natural liberation.
The Great Peacock is not endowed with this method of delivery by means
of a solvent; her stomach is incapable of preparing the corrosive
calculated to destroy, at any point, the defensive enclosure which is
now a prison-wall. Indeed, if I reverse the chrysalis in its cocoon,
opened and then closed with a few stitches, the Moth always dies, being
powerless to free herself. When the point to be forced is changed, the
release becomes impossible. To emerge from this shell, a genuine
strong-box, a special method is therefore necessary, one having no
relation to the chemical method of the Mulberry Bombyx. Let me
describe, as others have done before me, how things happen.
At the fore-end of the cocoon, a conical end, whereas the other is
rounded, the threads are not glued together; every elsewhere, the
silken web is cemented with a gummy product that turns it into a stout,
waterproof parchment. Those front threads, which are almost straight,
converge at their free end and form a cone-shaped series of palisades,
having as their common base the circle where the use of the gummy
cement is suddenly discontinued. The arrangement can best be compared
with the mouth of an Eel-pot, which the fish readily enters by
following the funnel of osier-switches, but from which the imprudent
one cannot get out again, because the narrow passage closes its
palisade at the least effort to push through.
Another very accurate comparison is provided by the Mouse-traps with an
entrance consisting of a bunch of wires arranged in a truncated cone.
Attracted by the bait, the rodent enters the orifice of the trap,
enlarging it with a gentle thrust; but, when it becomes a question of
departure, the wires, at first so tractable, become an insuperable
barrier of halberds. Both devices permit entrance and forbid exit. If
we invert the arrangement of the conical palisade, making it point
outwards from within, its action is reversed: exit is permitted and
entrance forbidden.
This is the case with the Great Peacock’s cocoon, which has a slight
improvement to its credit: its mouth, shaped like the Eel-pot or
Mouse-trap aforesaid, is formed of a numerous series of cones, fitting
one within the other and overlapping. In order to emerge, the Moth has
only to push her head in front of her; the several rows of uncemented
threads yield without difficulty. Once the recluse is liberated, these
threads resume their position, so that there is nothing outside to show
whether the cocoon is empty or inhabited.
Easy exit is not enough: there must also be an inviolable refuge during
the labour of metamorphosis. The cell whose door is open for exit must
have the same door closed against entrance, so that no evil-minded one
may make his way inside. The mechanism of the Eel-pot’s mouth admirably
fulfils this condition, which is as necessary to the safety of the
Great Peacock as the first. To enter through the multiple fences of
converging threads, which constitute a more effectual obstacle the
harder they are pushed, would be impossible to any creature that might
bethink itself of attempting to violate the dwelling. I am
well-acquainted with the secrets of this lock, which contrives, like
any fine piece of workmanship, to combine simple means with important
results; and yet I always stand amazed when, with an open cocoon in my
fingers, I try to pass a pencil through the entrance. When pushed
outwards from within, it passes immediately; when pushed inwards from
without, it is invincibly checked.
I am lingering over these details to show the importance which the good
construction of her palisade of threads possesses for the Great
Peacock. If ill-ordered, entangled and therefore intractable when
pushed, the series of boxed cones will offer an insurmountable
resistance and the Moth will perish, a victim of the caterpillar’s
imperfect art. If constructed with mathematical accuracy, but with
sparse rows of threads in insufficient numbers, it will leave the
retreat exposed to dangers from without and the chrysalis will become
the prey of some intruder, of whom there are many in search of
somnolent nymphs, forming easy victims. For the caterpillar, therefore,
this double-acting mouth is a work of the highest importance. It has to
expend upon it all that it possesses in foresight, in gleams of reason
and in art capable of modification when circumstances require; it must
in short give proof of the best of which its talents are capable. Let
us follow it in its labours; let us interpose the experimental test;
and we shall learn some curious facts.
The cocoon and its opening are constructed simultaneously. When it has
woven this or that part of the general wall, the caterpillar turns
about, if need be, and with its unbroken thread proceeds to continue
the palisade of converging filaments. To this end it pokes its head to
the end of the roughly-defined funnel and then withdraws it, doubling
the thread as it goes. This alternation of thrusts and withdrawals
results in a circle of doubled filaments, which do not adhere to one
another. The shift is not a long one; when the palisade is a row the
richer, the caterpillar resumes its work upon the shell, a task which
it again abandons to busy itself with the funnel; and so on, over and
over again, the emission of the gummy product being suspended when the
threads are to be left free and copiously effected when they have to be
stuck together in order to obtain a solid texture.
The exit-funnel is not, as we see, a piece of work executed
continuously; the caterpillar works at it intermittently, as the
general shell progresses. From the beginning to the end of its
spinning-period, so long as the reservoirs of silk are not exhausted,
it multiplies the tiers without neglecting the rest of the cocoon.
These tiers take the form of cones enclosed one within the other and of
increasingly obtuse angles, until the last to be spun are so flat as to
become almost level surfaces.
If nothing happen to disturb the worker, the work is performed with a
perfection that would do credit to a discerning industry capable of
realizing the why and wherefore of things. Can the caterpillar be said
to have any conception, however slight, of the importance of its task,
of the future function of its overlapping conical palisades? This is
what we are about to learn.
I take a pair of scissors and remove the conical extremity while the
spinner is working at the other end. The cocoon is now wide open. The
caterpillar soon turns about. It thrusts its head into the wide breach
which I have just made; it seems to be exploring the outside and
enquiring into the accident that has occurred. I expect to see it
repair the disaster and entirely reconstruct the cone destroyed by my
scissors. It does, in fact, work at it for a time; it erects a row of
converging threads; then, without paying further heed to the disaster,
it applies its spinnerets elsewhere and continues to thicken the
cocoon.
Grave doubts come to my mind: the cone built upon the breach consists
of sparse filaments; it is, moreover, very flat and does not project
anything like so much as the original cone. What I took at first to be
a work of repair is merely a work of continuation. The caterpillar, put
to the test by my tricks, has not modified the course of its work;
despite the imminence of the danger, it has confined itself to the tier
of threads which it would have fitted inside the preceding tier but for
the snip of my scissors.
I let things go on for a while; and, when the mouth has once again
acquired a certain solidity, I cut it off for the second time. The
insect displays the same lack of perspicacity as before, replacing the
absent cone by one with an even more obtuse angle, that is to say,
continuing its usual task, without any attempt at a thorough
restoration, despite the extreme urgency. If the store of silk were
nearly at an end, I should sympathize with the troubles of the
sorely-tried caterpillar doing its best to repair its house with the
scanty materials that remain at its disposal; but I see it foolishly
squandering its product on the additional upholstering of a shell which
may be strong enough as it is, while economizing to the point of
stinginess in the matter of the fence, which, if neglected, will leave
the cell and its inhabitant at the mercy of the first thief that comes
along. There is no lack of silk: the spinner applies layer upon layer
to the points that are unhurt; but at the breach it employs only the
quantity required under ordinary conditions. This is not economy
imposed by shortage; it is blind clinging to custom. And so my
commiseration changes to amazement in the presence of such profound
stupidity, which applies itself to the superfluous work of upholstery
in a dwelling henceforth uninhabitable, instead of attending, while
there is yet time, to the business of repairing the ruins.
I make my cut a third time. When the moment has come to resume the
series of boxed cones, the caterpillar arms the breach with bristles
arranged in a disk, as they appear in the last courses of the
undisturbed structure. This configuration shows that the end of the
task is at hand. The cocoon is strengthened for a little longer; then
rest ensues and the metamorphosis begins in a dwelling with a niggardly
fence to it, one which would not strike terror into the puniest
invader.
To sum up, the caterpillar, incapable of perceiving the dangers
attendant upon an incomplete palisade, resumes its work, after each
amputation of the cocoon, at the point where it had left it before the
accident. Instead of thoroughly restoring the ruined exit, which its
very abundant store of silk would allow it to do; instead of reerecting
on the breach a projecting cone of many layers, to replace the one
removed by my scissors, it runs up layers of threads that become
gradually flatter and flatter and form a continuation and not a
reconstruction of the missing layers. Moreover, this work of
fence-building, the need for which would seem imperious to any
reasoning creature, does not appear to preoccupy the caterpillar more
than usual, for it keeps on alternating this work with that of the
cocoon, which is much less urgent. Everything goes by rote, as though
the serious incident of the housebreaking had not occurred. In a word,
the caterpillar does not begin all over again a thing once made and
then destroyed; it continues it. The early stages of the work are
lacking; no matter: the sequel follows without any modification in the
plans.
It would be easy for me, if my argument were not already quite clear,
to give a host of similar examples showing plainly that the
intelligence of the insect is absolutely deficient in rational
discernment, even when the great perfection of the work would seem to
allow the artisan a certain perspicacity. We will confine ourselves for
the moment to the three cases which I have mentioned. The Pelopæus goes
on storing Spiders for an egg that has been removed; she perseveres in
making hunting-trips that are henceforth useless; she hoards victuals
that are destined to nourish nothing; she multiplies her battues to
fill with game a larder which is forthwith emptied by my tweezers;
lastly, she closes, with every customary care, a cell that no longer
contains anything whatever: she sets her seal on emptiness. She does
even absurder things: she plasters the site of her vanished nest,
covering an imaginary structure and putting a roof to a house which at
the moment is tucked away in my pocket. In the case of the Great
Peacock, the caterpillar, despite the certain loss of the coming Moth,
instead of beginning all over again the mouth of the Eel-pot cut down
by my scissors, quietly continues its spinning, without in any way
modifying the regular course of the work; and, when the time comes for
making the last tiers of defensive filaments, it erects them upon the
dangerous breach, but neglects to rebuild the ruined portion of the
barricade. Indifferent to the indispensable, it occupies itself with
the superfluous.
What are we to conclude from these facts? I would fain believe, for the
sake of my insects’ reputation, in some distraction on their part, in
some individual giddiness which would not taint the general
perspicacity; I should like to regard their aberrations merely as
isolated and exceptional actions, which would not affect their judgment
as a whole. Alas, a long series of glaring facts would impose silence
on my attempts at rehabilitation! Any species, no matter which, when
subjected to experimental tests, is guilty of similar inconsistencies
in the course of its disturbed industry. Constrained by the inexorable
logic of the facts, I therefore state the deductions suggested by
observation as follows: the insect is neither free nor conscious in its
industry, which in its case is an external function with phases
regulated almost as strictly as the phases of an internal function,
such as digestion. It builds, weaves, hunts, stabs and paralyses, even
as it digests, even as it secretes the poison of its sting, the silk of
its cocoon or the wax of its combs, always without the least
understanding of the means or the end. It is ignorant of its wonderful
talents just as the stomach is ignorant of its skilful chemistry. It
can add nothing essential to them nor subtract anything from them, any
more than it is able to increase or diminish the pulsations of its
dorsal vessel.
Test it with an accident and you affect it not at all: such as it is in
the undisturbed exercise of its calling, such it will remain should
circumstances arise demanding some modification in the conduct of its
task. Experience does not teach it; time does not awaken a glimmer in
the darkness of its unconsciousness. Its art, perfect in its
speciality, but inept in the face of the slightest new difficulty, is
handed down immutably, as the art of the suction-pump is handed down to
the babe at the breast. To expect the insect to alter the essential
points of its industry is to hope that the babe will change its manner
of sucking. Both equally ignorant of what they are doing, they
persevere in the method prescribed for the safeguarding of the species,
precisely because their ignorance forbids them to make any sort of
essay or attempt.
The insect, then, lacks the aptitude for reflection, the aptitude that
harks back and reverts to the antecedent, without which the consequent
would lose all its value. In the phases of its industry, each action
accomplished counts as valid by the mere fact that it has been
accomplished; the insect does not go back to it, should some accident
demand; the consequent follows without troubling about the missing
antecedent. A blind impulse urges it from one act to a second, from
this second to a third and so on until the task is completed; but it is
impossible for the insect to reascend the current of its activity
should accidental conditions arise and call for this, however
imperatively. Having passed through the complete cycle, the work is
considered to be most logically performed by a worker devoid of all
logic.
The stimulus to labour is the bait of pleasure, that chief motive-power
in the animal. The mother has no foreknowledge whatever of her future
larva; she does not build, does not hunt, does not hoard with the
conscious aim of rearing a family. The real object of her work is
hidden from her; the accessory but exciting aim, the pleasure
experienced, is her only guide. The Pelopæus feels a keen satisfaction
when she crams a cell full with Spiders; and she goes on hunting with
imperturbable spirit after the removal of the egg from the cell has
made provisions useless. She delights in plastering the outside of her
nest with mud and she continues to putty the site of her nest, after it
has been detached from the wall, without suspecting the futility of her
stucco. And so with the others. To reproach them for their aberrations
we must assume that they possess a tiny glimmer of reason, as Darwin
[48] would have us believe; if they have it not, the reproach falls to
the ground and their aberrant acts are the inevitable result of an
unconsciousness diverted from its normal paths.