THE IGNORANCE OF INSTINCT
The Sphex has shown us how infallibly and with what transcendental art
she acts when guided by the unconscious inspiration of her instinct;
she is now going to show us how poor she is in resource, how limited in
intelligence, how illogical even, in circumstances outside of her
regular routine. By a strange inconsistency, characteristic of the
instinctive faculties, profound wisdom is accompanied by an ignorance
no less profound. To instinct nothing is impossible, however great the
difficulty may be. In building her hexagonal cells, with their floors
consisting of three lozenges, the Bee solves with absolute precision
the arduous problem of how to achieve the maximum result at a minimum
cost, a problem whose solution by man would demand a powerful
mathematical mind. The Wasps whose larvæ live on prey display in their
murderous art methods hardly rivalled by those of a man versed in the
intricacies of anatomy and physiology. Nothing is difficult to
instinct, so long as the act is not outside the unvarying cycle of
animal existence; on the other hand, nothing is easy to instinct, if
the act is at all removed from the course usually pursued. The insect
which astounds us, which terrifies us with its extraordinary
intelligence, surprises us, the next moment, with its stupidity, when
confronted with some simple fact that happens to lie outside its
ordinary practice. The Sphex will supply us with a few instances.
Let us follow her dragging her Ephippiger home. If fortune smile upon
us, we may witness some such little scene as that which I will now
describe. When entering her shelter under the rock, where she has made
her burrow, the Sphex finds, perched on a blade of grass, a Praying
Mantis, a carnivorous insect which hides cannibal habits under a pious
appearance. The danger threatened by this robber ambushed on her path
must be known to the Sphex, for she lets go her game and pluckily
rushes upon the Mantis, to inflict some heavy blows and dislodge her,
or at all events to frighten her and inspire her with respect. The
robber does not move, but closes her lethal machinery, the two terrible
saws of the arm and fore-arm. The Sphex goes back to her capture,
harnesses herself to the antennæ and boldly passes under the blade of
grass whereon the other sits perched. By the direction of her head we
can see that she is on her guard and that she holds the enemy rooted,
motionless, under the menace of her eyes. Her courage meets with the
reward which it deserves: the prey is stored away without further
mishap.
A word more on the Praying Mantis, or, as they say in Provence, lou
Prégo Diéou, the Pray-to-God. Her long, pale-green wings, like
spreading veils, her head raised heavenwards, her folded arms, crossed
upon her breast, are in fact a sort of travesty of a nun in ecstasy.
And yet she is a ferocious creature, loving carnage. Though not her
favourite spots, the work-yards of the various Digger-wasps receive her
visits pretty frequently. Posted near the burrows, on some bramble or
other, she waits for chance to bring within her reach some of the
arrivals, forming a double capture for her, as she seizes both the
huntress and her prey. Her patience is long put to the test: the Wasp
suspects something and is on her guard; still, from time to time, a
rash one gets caught. With a sudden rustle of wings half-unfurled as by
the violent release of a clutch, the Mantis terrifies the newcomer, who
hesitates for a moment, in her fright. Then, with the sharpness of a
spring, the toothed fore-arm folds back on the toothed upper arm; and
the insect is caught between the blades of the double saw. It is as
though the jaws of a Wolf-trap were closing on the animal that had
nibbled at its bait. Thereupon, without unloosing the cruel machine,
the Mantis gnaws her victim by small mouthfuls. Such are the ecstasies,
the prayers, the mystic meditations of the Prégo Diéou.
Of the scenes of carnage which the Praying Mantis has left in my
memory, let me relate one. The thing happens in front of a work-yard of
Bee-eating Philanthi. These diggers feed their larvæ on Hive-bees, whom
they catch on the flowers while gathering pollen and honey. If the
Philanthus who has made a capture feels that her Bee is swollen with
honey, she never fails, before storing her, to squeeze her crop, either
on the way or at the entrance of the dwelling, so as to make her
disgorge the delicious syrup, which she drinks by licking the tongue
which her unfortunate victim, in her death-agony, sticks out of her
mouth at full length. This profanation of a dying creature, whose enemy
squeezes its belly to empty it and feast on the contents, has something
so hideous about it that I should denounce the Philanthus as a brutal
murderess, if animals were capable of wrongdoing. At the moment of some
such horrible banquet, I have seen the Wasp, with her prey, seized by
the Mantis: the bandit was rifled by another bandit. And here is an
awful detail: while the Mantis held her transfixed under the points of
the double saw and was already munching her belly, the Wasp continued
to lick the honey of her Bee, unable to relinquish the delicious food
even amid the terrors of death. Let us hasten to cast a veil over these
horrors.
We will return to the Sphex, with whose burrow we must make ourselves
acquainted before we go further. This burrow is a hole made in fine
sand, or rather in a sort of dust at the bottom of a natural shelter.
Its entrance-passage is very short, merely an inch or two, without a
bend, and leads to a single, roomy, oval chamber. The whole thing is a
rough den, hastily dug out, rather than a leisurely and artistically
excavated dwelling. I have explained that the reason for this
simplicity is that the game is captured first and set down for a moment
on the hunting-field while the Wasp hurriedly makes a burrow in the
vicinity, a method of procedure which allows of but one chamber or cell
to each retreat. For who can tell whither the chances of the day will
lead the huntress for her second capture? The prisoner is heavy and the
burrow must therefore be near; so to-day’s home, which is too far away
for the next Ephippiger to be conveyed to it, cannot be utilized
to-morrow. Thus, as each prey is caught, there is a fresh excavation, a
fresh burrow, with its single chamber, now here, now there. Having said
this, we will try a few experiments to see how the insect behaves when
we create circumstances new to it.
EXPERIMENT I
A Sphex, dragging her prey along, is a few inches from the burrow.
Without disturbing her, I cut with a pair of scissors the Ephippiger’s
antennæ, which the Wasp, as we know, uses for harness-ropes. On
recovering from the surprise caused by the sudden lightening of her
load, the Sphex goes back to her victim and, without hesitation, now
seizes the root of the antenna, the short stump left by the scissors.
It is very short indeed, hardly a millimetre; [31] no matter: it is
enough for the Sphex, who grips this fag-end of a rope and resumes her
hauling. With the greatest precaution, so as not to injure the Wasp, I
now cut the two antennary stumps level with the skull. Finding nothing
left to catch hold of at the familiar points, the insect seizes, close
by, one of the victim’s long palpi and continues its hauling-work,
without appearing at all perturbed by this change in the harness. I
leave it alone. The prey is brought home and placed so that its head
faces the entrance to the burrow; and the Wasp goes in by herself, to
make a brief inspection of the inside of the cell before proceeding to
warehouse the provisions. Her behaviour reminds us of that of the
Yellow-winged Sphex in similar circumstances. I take advantage of this
short moment to seize the abandoned prey, remove all its palpi and
place it a little farther off, about half a yard from the burrow. The
Sphex reappears and goes straight to her captive, whom she has seen
from her threshold. She looks at the top of the head, she looks
underneath, on either side, and finds nothing to take hold of. A
desperate attempt is made: the Wasp, opening wide her mandibles, tries
to grab the Ephippiger by the head; but the pincers have not a
sufficient compass to take in so large a bulk and they slip off the
round, polished skull. She makes several fresh endeavours, each time
without result. She is at length convinced of the uselessness of her
efforts. She draws back a little to one side and appears to be
renouncing further attempts. One would say that she was discouraged; at
least, she smooths her wings with her hind-legs, while with her front
tarsi, which she first puts into her mouth, she washes her eyes. This,
so it has always seemed to me, is a sign in Hymenoptera of giving up a
job.
Nevertheless there is no lack of parts by which the Ephippiger might be
seized and dragged along as easily as by the antennæ and the palpi.
There are the six legs, there is the ovipositor: all organs slender
enough to be gripped boldly and to serve as hauling-ropes. I agree that
the easiest way to effect the storing is to introduce the prey head
first, drawn down by the antennæ; but it would enter almost as readily
if drawn by a leg, especially one of the front legs, for the orifice is
wide and the passage short or sometimes even non-existent. Then how is
it that the Sphex did not once try to seize one of the six tarsi or the
tip of the ovipositor, whereas she attempted the impossible, the
absurd, in striving to grip, with her much too short mandibles, the
huge skull of her prey? Can it be that the idea did not occur to her?
Then we will try to suggest it.
I offer her, right under her mandibles, first a leg, next the end of
the abdominal rapier. The insect obstinately refuses to bite; my
repeated blandishments lead to nothing. A singular huntress, to be
embarrassed by her game, not knowing how to seize it by a leg when she
is not able to take it by the horns! Perhaps my prolonged presence and
the unusual events that have just occurred have disturbed her
faculties. Then let us leave the Sphex to herself, between her
Ephippiger and her burrow; let us give her time to collect herself and,
in the calm of solitude, to think out some way of managing her
business. I leave her therefore and continue my walk; and, two hours
later, I return to the same place. The Sphex is gone, the burrow is
still open, and the Ephippiger is lying just where I placed her.
Conclusion: the Wasp has tried nothing; she went away, abandoning
everything, her home and her game, when, to utilize them both, all that
she had to do was to take her prey by one leg. And so this rival of
Flourens, who but now was startling us with her cleverness as she
dexterously squeezed her victim’s brain to produce lethargy, becomes
incredibly helpless in the simplest case outside her usual habits. She,
who so well knows how to attack a victim’s thoracic ganglia with her
sting and its cervical ganglia with her mandibles; she, who makes such
a judicious difference between a poisoned prick annihilating the vital
influence of the nerves for ever and a pressure causing only momentary
torpor, cannot grip her prey by this part when it is made impossible
for her to grip it by any other. To understand that she can take a leg
instead of an antenna is utterly beyond her powers. She must have the
antenna, or some other string attached to the head, such as one of the
palpi. If these cords did not exist, her race would perish, for lack of
the capacity to solve this trivial problem.
EXPERIMENT II
The Wasp is engaged in closing her burrow, where the prey has been
stored and the egg laid upon it. With her front tarsi she brushes her
doorstep, working backwards and sweeping into the entrance a stream of
dust which passes under her belly and spurts behind in a parabolic
spray as continuous as a liquid spray, so nimble is the sweeper in her
actions. From time to time the Sphex picks out with her mandibles a few
grains of sand, so many solid blocks which she inserts one by one into
the mass of dust, causing it all to cake together by beating and
compressing it with her forehead and mandibles. Walled up by this
masonry, the entrance-door soon disappears from sight.
I intervene in the middle of the work. Pushing the Sphex aside, I
carefully clear the short gallery with the blade of a knife, take away
the materials that close it and restore full communication between the
cell and the outside. Then, with my forceps, without damaging the
edifice, I take the Ephippiger from the cell, where she lies with her
head at the back and her ovipositor towards the entrance. The Wasp’s
egg is on the victim’s breast, at the usual place, the root of one of
the hinder thighs: a proof that the Sphex was giving the finishing
touch to the burrow, with the intention of never returning.
Having done this and put the stolen prey safely away in a box, I yield
my place to the Sphex, who has been on the watch beside me while I was
rifling her home. Finding the door open, she goes in and stays for a
few moments. Then she comes out and resumes her work where I
interrupted it, that is to say, she starts conscientiously stopping the
entrance to the cell by sweeping dust backwards and carrying grains of
sand, which she continues to heap up with scrupulous care, as though
she were doing useful work. When the door is once again thoroughly
walled up, the insect brushes itself, seems to give a glance of
satisfaction at the task accomplished, and finally flies away.
The Sphex must have known that the burrow contained nothing, because
she went inside and even stayed there for some time; and yet, after
this inspection of the pillaged abode, she once more proceeds to close
up the cell with the same care as though nothing out of the way had
happened. Can she be proposing to use this burrow later, to return to
it with a fresh victim and lay a new egg there? If so, her work of
closing would be intended to prevent the access of intruders to the
dwelling during her absence; it would be a measure of prudence against
the attempts of other diggers who might covet the ready-made chamber;
it might also be a wise precaution against internal dilapidations. And,
as a matter of fact, some Hunting Wasps do take care to protect the
entrance to the burrow by closing it temporarily, when the work has to
be suspended for a time. Thus I have seen certain Ammophilæ, whose
burrow is a perpendicular shaft, block the entrance to the home with a
small flat stone when the insect goes off hunting or ceases its mining
operations at sunset, the hour for striking work. But this is a slight
affair, a mere slab laid over the mouth of the shaft. When the insect
comes, it only takes a moment to remove the little flat stone; and the
entrance is free.
On the other hand, the obstruction which we have just seen built by the
Sphex is a solid barrier, a stout piece of masonry, where dust and
gravel form alternate layers all the way down the passage. It is a
definite performance and not a provisional defence, as is proved by the
care with which it is constructed. Besides, as I think I have shown
pretty clearly, it is very doubtful, considering the way in which she
acts, whether the Sphex will ever return to make use of the home which
she has prepared. The next Ephippiger will be caught elsewhere; and the
warehouse destined to receive her will be dug elsewhere too. But these,
after all, are only arguments: let us rather have recourse to
experiment, which is more conclusive here than logic.
I allowed nearly a week to elapse, in order to give the Sphex time to
return to the burrow which she had so methodically closed and to make
use of it for her next laying if such were her intention. Events
corresponded with the logical inferences: the burrow was in the
condition wherein I left it, still firmly closed, but without
provisions, egg or larva. The proof was decisive: the Wasp had not been
back.
So the plundered Sphex enters her house, makes a leisurely inspection
of the empty chamber, and, a moment afterwards, behaves as though she
had not perceived the disappearance of the bulky prey which but now
filled the cell. Did she, in fact, fail to notice the absence of the
provisions and the egg? Is she, who is so clear-sighted in her
murderous proceedings, dense enough not to realize that the cell is
empty? I dare not accuse her of such stupidity. She is aware of it. But
then why that other piece of stupidity which makes her close—and very
conscientiously close—an empty burrow, one which she does not purpose
to victual later? Here the work of closing is useless, is supremely
absurd; no matter: the insect performs it with the same ardour as
though the larva’s future depended on it. The insect’s various
instinctive actions are then fatally linked together. Because one thing
has been done, a second thing must inevitably be done to complete the
first or to prepare the way for its completion; and the two acts depend
so closely upon each other that the performing of the first entails
that of the second, even when, owing to casual circumstances, the
second has become not only inopportune but sometimes actually opposed
to the insect’s interests. What object can the Sphex have in blocking
up a burrow which has become useless, now that it no longer contains
the victim and the egg, and which will always remain useless, since the
insect will not return to it? The only way to explain this inconsequent
action is to look upon it as the inevitable complement of the actions
that went before. In the normal order of things, the Sphex hunts down
her prey, lays an egg and closes her burrow. The hunting has been done;
the game, it is true, has been withdrawn by me from the cell; never
mind: the hunting has been done, the egg has been laid; and now comes
the business of closing up the home. This is what the insect does,
without another thought, without in the least suspecting the futility
of her present labours.
EXPERIMENT III
To know everything and to know nothing, according as it acts under
normal or exceptional conditions: that is the strange antithesis
presented by the insect race. Other examples, also drawn from the Sphex
tribe, will confirm this conclusion. The White-edged Sphex (S.
albisecta) attacks medium-sized Locusts, whereof the different species
to be found in the neighbourhood of the burrow all furnish her with
their tribute of victims. Because of the abundance of these Acridians,
there is no need to go hunting far afield. When the burrow, which takes
the form of a perpendicular shaft, is ready, the Sphex merely explores
the purlieus of her lair, within a small radius, and is not long in
finding some Locust browsing in the sunshine. To pounce upon her and
sting her, despite her kicking, is to the Sphex the matter of a moment.
After some fluttering of its wings, which unfurl their carmine or azure
fan, after some drowsy stretching of its legs, the victim ceases to
move. It has now to be brought home, on foot. For this laborious
operation the Sphex employs the same method as her kinswomen, that is
to say, she drags her prize along between her legs, holding one of its
antennæ in her mandibles. If she encounters some grassy jungle, she
goes hopping and flitting from blade to blade, without ever letting
slip her prey. When at last she comes within a few feet of her
dwelling, she performs a manœuvre which is also practised by the
Languedocian Sphex; but she does not attach as much importance to it,
for she frequently neglects it. Leaving her captive on the road, the
Wasp hurries home, though no apparent danger threatens her abode, and
puts her head through the entrance several times, even going part of
the way down the burrow. She next returns to the Locust and, after
bringing her nearer the goal, leaves her a second time to revisit the
burrow. This performance is repeated over and over again, always with
the same anxious haste.
These visits are sometimes followed by grievous accidents. The victim,
rashly abandoned on hilly ground, rolls to the bottom of the slope; and
the Sphex on her return, no longer finding it where she left it, is
obliged to seek for it, sometimes fruitlessly. If she find it, she must
renew a toilsome climb, which does not prevent her from once more
abandoning her booty on the same unlucky declivity. Of these repeated
visits to the mouth of the shaft, the first can be very logically
explained. The Wasp, before arriving with her heavy burden, inquires
whether the entrance to the home be really clear, whether nothing will
hinder her from bringing in her game. But, once this first
reconnaissance is made, what can be the use of the rest, following one
after the other, at close intervals? Is the Sphex so volatile in her
ideas that she forgets the visit which she has just paid and runs
afresh to the burrow a moment later, only to forget this new inspection
also and to start doing the same thing over and over again? That would
be a memory with very fleeting recollections, whence the impression
vanished almost as soon as it was produced. Let us not linger too long
on this obscure point.
At last the game is brought to the brink of the shaft, with its antennæ
hanging down the hole. We now again see, faithfully imitated, the
method employed in the like case by the Yellow-winged Sphex and also,
but under less striking conditions, by the Languedocian Sphex. The Wasp
enters alone, inspects the interior, reappears at the entrance, lays
hold of the antennæ and drags the Locust down. While the
Locust-huntress was making her examination of the home, I have pushed
her prize a little farther back; and I obtained results similar in all
respects to those which the Cricket-huntress gave me. Each Sphex
displays the same obstinacy in diving down her burrow before dragging
in the prey. Let us recall here that the Yellow-winged Sphex does not
always allow herself to be caught by this trick of pulling away her
Cricket. There are picked tribes, strong-minded families which, after a
few disappointments, see through the experimenter’s wiles and know how
to baffle them. But these revolutionaries, fit subjects for progress,
are the minority; the remainder, mulish conservatives clinging to the
old manners and customs, are the majority, the crowd. I am unable to
say whether the Locust-huntress also varies in ingenuity according to
the district which she hails from.
But here is something more remarkable; and it is this with which I
wanted to conclude the present experiment. After repeatedly withdrawing
the White-edged Sphex’ prize from the mouth of the pit and compelling
her to come and fetch it again, I take advantage of her descent to the
bottom of the shaft to seize the prey and put it in a place of safety
where she cannot find it. The Sphex comes up, looks about for a long
time and, when she is convinced that the prey is really lost, goes down
into her home again. A few moments after, she reappears. Is it with the
intention of resuming the chase? Not the least in the world: the Sphex
begins to stop up the burrow. And what we see is not a temporary
closing, effected with a small flat stone, a slab covering the mouth of
the well; it is a final closing, carefully done with dust and gravel
swept into the passage until it is filled up. The White-edged Sphex
makes only one cell at the bottom of her shaft and puts one head of
game into this cell. That single Locust has been caught and dragged to
the edge of the hole. If she was not stored away, it was not the
huntress’s fault, but mine. The Wasp performed her task according to
the inflexible rule; and, also according to the inflexible rule, she
completes her work by stopping up the dwelling, empty though it be. We
have here an exact repetition of the useless exertions made by the
Languedocian Sphex whose home has just been plundered.
EXPERIMENT IV
It is almost impossible to make certain whether the Yellow-winged
Sphex, who constructs several cells at the end of the same passage and
stacks several Crickets in each, is equally illogical when accidentally
disturbed in her proceedings. A cell can be closed though empty or
imperfectly victualled, and the Wasp will none the less continue to
come to the same burrow in order to work at the others. Nevertheless, I
have reason to believe that this Sphex is subject to the same
aberrations as her two kinswomen. My conviction is based on the
following facts: the number of Crickets found in the cells, when all
the work is done, is usually four to each cell, although it is not
uncommon to find only three, or even two. Four appears to me to be the
normal number, first, because it is the most frequent and, secondly,
because, when rearing young larvæ dug up while they were still engaged
on their first joint, I found that all of them, those actually provided
with only two or three pieces of game as well as those which had four,
easily managed the various Crickets wherewith I served them one by one,
up to and including the fourth, but that after this they refused all
nourishment, or barely touched the fifth ration. If four Crickets are
necessary to the larva to acquire the full development called for by
its organization, why are sometimes only three, sometimes only two
provided for it? Why this enormous difference in the quantity of the
victuals, some larvæ having twice as much as the others? It cannot be
because of any difference in the size of the dishes provided to satisfy
the grub’s appetite, for all have very much the same dimensions; and it
can therefore be due only to the wastage of game on the way. We find,
in fact, at the foot of the banks whose upper stages are occupied by
the Sphex-wasps, Crickets that have been paralysed but lost, owing to
the slope of the ground, down which they have slipped when the
huntresses have momentarily left them, for some reason or other. These
Crickets fall a prey to the Ants and Flies; and the Sphex-wasps who
come across them take good care not to pick them up, for, if they did,
they would themselves be admitting enemies into the house.
These facts seem to me to prove that, while the Yellow-winged Sphex’
arithmetical powers enable her to calculate exactly how many victims to
capture, she cannot achieve a census of those which have safely reached
their destination. It is as though the insect had no mathematical guide
beyond an irresistible impulse that prompts her to hunt for game a
definite number of times. When the Sphex has made the requisite number
of journeys, when she has done her utmost to store the captures that
result from these, her work is ended; and she closes the cell whether
completely or incompletely provisioned. Nature has endowed her with
only those faculties called for in ordinary circumstances by the
interests of her larvæ; and, as these blind faculties, which cannot be
modified by experience, are sufficient for the preservation of the
race, the insect is unable to go beyond them.
I conclude therefore as I began: instinct knows everything, in the
undeviating paths marked out for it; it knows nothing, outside those
paths. The sublime inspirations of science and the astounding
inconsistencies of stupidity are both its portion, according as the
insect acts under normal or accidental conditions.