The Sphex has just shown us with what infallible, transcendent art she
acts, guided by the unconscious inspiration of instinct: she will now
show how poor she is in resources, how limited in intelligence, and
even illogical in cases somewhat out of her usual line. By a strange
contradiction, characteristic of the instinctive faculties, with deep
science is associated ignorance not less deep. Nothing is impossible to
instinct, however great be the difficulty. In constructing her
hexagonal cells with their floor of three lozenge-shaped pieces, the
bee resolves, with absolute precision, the arduous problems of maximum
and minimum, to solve which man would need a powerful, mathematical
mind. Hymenoptera, whose larvæ live on prey, have methods in their
murderous art hardly equalled by those of a man versed in the most
delicate mysteries of anatomy and physiology. Nothing is difficult to
instinct so long as the action moves in the unchanging groove allotted
to the animal, but, again, nothing is easy to instinct if the action
deviates from it. The very insect which amazes us and alarms us by its
high intelligence will, a moment later, astonish us by its stupidity
before some fact extremely simple, but strange to its usual habits. The
Sphex will offer an example.
Let us follow her dragging home an ephippiger. If fortune favour us, we
may be present at a little scene which I will describe. On entering the
shelter under a rock where the burrow is made, the Sphex finds, perched
on a blade of grass, a carnivorous insect which, under a most
sanctimonious aspect, hides the morals of a cannibal. The danger
threatened by this bandit in ambush on her path must be known to the
Sphex, for she leaves her game and runs bravely at the Mantis to
administer some sharp blows and dislodge, or at all events, alarm and
inspire it with respect. It does not move, but closes its deadly
weapons—the two terrible saws of the arm and forearm. The Sphex returns
to her prey, harnesses herself to the antennæ, and passes audaciously
under the blade of grass where the Mantis sits. From the direction of
her head one can see that she is on her guard, and is holding the enemy
motionless under her threatening eyes. Such courage is duly rewarded;
the prey is stored without further misadventure.
A word more of the Praying Mantis, the Prégo Diéou as it is called in
Provence, i.e. the Pray-to-God. And, indeed, its long, pale green
wings, like ample veils, its head upraised to heaven, its arms folded
and crossed on its breast, give it a false resemblance to a nun in
ecstatic devotion. All the same, it is a ferocious creature, bent on
carnage. Although not especially favourite hunting-grounds, the
workshops of various burrowing Hymenoptera are often visited by it.
Posted on some bush near the burrows, it waits until chance brings some
Sphex returning home within reach, thus achieving a double capture,
catching together Sphex and prey. Its patience is long tried; the Sphex
is suspicious and on her guard, but from time to time a rash one lets
herself be caught. By a sudden rustle of half-spread wings, as by a
convulsive movement, the Mantis terrifies the approaching Sphex, which
hesitates for a moment, and then with the suddenness of a spring the
toothed forearm folds back on an arm also toothed, and the insect is
seized between the blades of the double saw, as though the jaws of a
wolf trap were closing on the beast as it takes the bait. Then, without
unclosing the cruel machine, the Mantis gnaws little mouthfuls of its
victim. Such are the ecstasies, the prayers, and the mystic meditations
of the Prégo Diéou.
Among the scenes of carnage which the Mantis has left in my memory, let
me describe the following. It passes before a working-place of
Philanthus apivorus. These miners nourish their larvæ with hive-bees,
which they seize on flowers while collecting pollen and honey. If the
Philanthus feels that the bee is full of honey, it does not fail to
squeeze it before storing it, either on the way, or at the entrance of
the hole, to make it disgorge the delicious liquid; this it drinks by
licking the tongue of the unfortunate bee, which, dying, extends it at
full length. This profanation of a dying creature, squeezed by its
murderer to empty its body and enjoy the contents, has something so
hideous that I should call it a crime if a Philanthus could be held
responsible. In the midst of this horrible banquet I have seen both
murderer and prey seized by the Mantis; the robber was plundered by a
second robber. Horrible to relate, while the Mantis held it
transpierced by the points of the double saw, and was already gnawing
the under parts, the Philanthus went on licking the honey, unable to
abandon the delicious food even in the throes of death. Let us cast a
veil over these horrors.
We return to the Sphex, with whose burrow we must make acquaintance
before going further. It is made of fine sand, or rather in the fine
dust at the bottom of a natural shelter. Its passage is very short—an
inch or two without a turn, leading into a single spacious oval
chamber, and all is a rude, hastily made den, rather than a dwelling
hollowed with art and leisure. I have already said that the captured
prey, left for a brief moment or two where it was hunted, is the cause
of the simplicity of this abode and of there being but one chamber or
cell to each hollow. For who can say whither the chances of the day’s
hunt may lead? The dwelling must be near the heavy prey, and to-day’s
abode, too far off to admit of carrying the second ephippiger there,
cannot be used to-morrow. Thus each time prey is caught there must be
new digging out—a new burrow with its one cell, now here, now there.
Now let us try some experiments to see how the insect behaves amid
circumstances new to it.
First experiment.—A Sphex, dragging her prey, is at a few inches from
her burrow. Without disturbing her I cut the antennæ of the ephippiger,
which we already know serve as harness. Having recovered from her
astonishment at the sudden lightening of her load, the Sphex returns
and unhesitatingly seizes the base of the antennæ, the short stumps not
cut off. Very short they are—hardly a millimetre long; no matter, they
suffice for the Sphex, who grips what remains of her ropes and drags
anew. With many precautions not to hurt her, I cut off the two stumps,
now level with the skull. Finding nothing to seize at the parts
familiar to her, she takes hold on one side of one of the long palpi of
her victim, and drags it, not at all put out by this modification in
her style of harnessing herself. I leave her alone. The prey is got
home and placed with its head to the mouth of the burrow. The Sphex
enters to make a short inspection of the interior before proceeding to
store provisions. Her tactics recall those of S. flavipennis in like
circumstances. I profit by this brief moment to take the abandoned
prey, deprive it of all its palpi, and place it a little farther off—a
pace from the burrow. The Sphex reappears and goes straight to her
game, which she saw from her threshold. She seeks above the head, she
seeks below, on one side, and finds nothing to seize. A desperate
attempt is made; opening wide her mandibles she tries to grasp the
ephippiger by the head, but her pincers cannot surround anything so
large, and slip off the round, polished skull. She tries several times
in vain; at length, convinced of the futility of her efforts, draws
back, and seems to renounce further attempts. She appears
discouraged—at least she smooths her wings with her hind feet, while
with her front tarsi, first passing them through her mouth, she washes
her eyes, a sign among Hymenoptera, as I believe, that they give a
thing up.
Yet there were points by which the ephippiger might be seized and
dragged as easily as by the antennæ and palpi. There are the six feet,
there is the ovipositor—all organs slender enough to be thoroughly
grasped and used as traction ropes. I own that the easiest way of
getting the prey into the storehouse is to introduce it head first by
the antennæ; yet, drawn by one foot, especially a front one, it would
enter almost as easily, for the orifice is wide and the passage short,
even if there be one. How came it then that the Sphex never once tried
to seize one of the six tarsi or the point of the ovipositor, while she
did make the impossible, absurd attempt to grip with mandibles far too
short the huge head of her prey? Perhaps the idea did not occur to her.
Let us try to suggest it. I place under her mandibles first a foot,
then the end of the abdominal sabre. She refuses obstinately to bite;
my repeated solicitations come to nothing. A very odd kind of hunter
this to be so embarrassed by her game and unable to think of seizing it
by a foot if it cannot be taken by the horns! Perhaps my presence and
all these unusual events may have troubled her faculties; let us leave
her to herself, with her burrow and ephippiger, and give her time to
consider and to imagine in the calm of solitude some means of managing
the business. I walked away and returned in a couple of hours to find
the Sphex gone, the burrow open, and the ephippiger where I had laid
it. The conclusion is that the Sphex tried nothing, but departed,
abandoning home, game—everything, when to utilise them all that was
needed would have been to take the prey by one foot. Thus this rival of
Flourens, who just now startled us by her science when pressing the
brain to induce lethargy, is invariably dull when the least unusual
event occurs. The Sphex, which knows so well how to reach the thoracic
ganglia of a victim with her sting, and those of the brain with her
mandibles, and which makes such a judicious difference between a
poisoned sting that would destroy the vital influence of the nerves,
and compression causing only momentary torpor, cannot seize her prey in
a new way. To understand that a foot may be taken instead of the
antennæ is impossible; nothing will do but the antennæ or another
filament of the head or one of the palpi. For want of these ropes her
whole race would perish, unable to surmount this trifling difficulty.
Second experiment.—The Sphex is busy closing her burrow where the prey
is stored and the egg laid. With her fore tarsi she sweeps backward
before her door, and launches from the entrance a spurt of dust, which
passes beneath her, and springs up behind in a parabolic curve as
continuous as if it were a slender stream of some liquid, so rapidly
does she sweep. From time to time she chooses some sand grains with her
mandibles, strengthening materials inserted singly in the dusty mass.
To consolidate this she beats it with her head, and heaps it with her
mandibles. Walled up by this masonry, the entrance rapidly disappears.
In the midst of the work I intervene. Having put the Sphex aside I
clear out the short gallery carefully with the blade of a knife, take
away the materials which block it, and entirely restore the
communication of the cell with the outer air. Then, without injuring
the edifice, I draw the ephippiger out of the cell where it is lying
with its head to the far end, and its ovipositor to the entrance. The
egg is as usual on its breast, near the base of one of the hind legs—a
proof that the Sphex had given her last touch to the burrow, and would
never return. These dispositions made, and the ephippiger placed safely
in a box, I gave up my place to the Sphex, who had been watching while
her domicile was rifled. Finding the entrance open, she entered and
remained some moments, then came forth and took up her work where I
interrupted it, beginning to stop the entrance conscientiously,
sweeping the dust backward, and transporting sand grains to build them
with minute care, as if doing a useful work. The orifice being again
thoroughly blocked, she brushed herself, seemed to give a glance of
satisfaction at her work, and finally flew off.
Yet she must have known that the burrow was empty, since she had gone
inside, and made prolonged stay, but yet after this visit to the
plundered dwelling, she set to work to close it with as much care as if
nothing had happened. Did she propose to turn it later to account,
returning with a fresh prey, and laying a new egg? In that case the
burrow was closed to defend it from indiscreet visitors while the Sphex
was away. Or it was a measure of prudence against other miners who
might covet a ready-made chamber, or a wise precaution against internal
wear and tear, and, in fact, some predatory Hymenoptera are careful
when obliged to suspend work to defend the mouth of their burrow by
closing it up temporarily. I have seen certain Ammophilæ, whose burrow
is a vertical well, close the entrance with a little flat stone when
the insect goes a-hunting, or stops mining when the hour to leave off
work comes at sunset. But in that case the stoppage is slight—a mere
slab set on the top of the well. It takes but a moment when the insect
comes to displace the little flat stone, and the door is open. But what
we have just seen the Sphex construct is a solid barrier—strong
masonry, where layers of alternate dust and gravel occupy the whole
passage. It is definitive, and no temporary work, as is sufficiently
shown by the careful way in which it is constructed. Besides, as I
think I have already proved, it is very doubtful, considering the
manner in which she acted, whether the Sphex would return to use the
dwelling which she had prepared. A new ephippiger will be caught
elsewhere, and elsewhere too will the storehouse destined for it be
hollowed. As, however, these are but conclusions drawn by reasoning,
let us consult experiment, more conclusive here than logic. I let
nearly a week pass in order to allow the Sphex to return to the burrow
so methodically closed, and use it if she liked for her nest-laying.
Events answered to the logical deduction; the burrow was just as I had
left it, well closed, but without food, egg, or larva. The
demonstration was decisive; the Sphex had not returned.
Thus we see the plundered Sphex go into her house, pay a leisurely
visit to the empty chamber, and the next moment behave as if she had
not perceived the absence of the big prey which a little while before
had encumbered the cell. Did she not realise the absence of food and
egg? Was she really so dull—she, so clear-sighted when playing the
murderer—that the cell was empty? I dare not accuse her of such
stupidity. She did perceive it. But why then that other piece of
stupidity which made her close, and very conscientiously too, an empty
chamber which she did not mean to store? It was useless—downright
absurd—to do this, and yet she worked with as much zeal as if the
future of the larva depended on it. The various instinctive actions of
insects are then necessarily connected; since one thing has been done,
such another must inevitably follow to complete the first, or prepare
the way for the next, and the two acts are so necessarily linked that
the first must cause the second, even when by some chance this last has
become not only superfluous, but sometimes contrary to the creature’s
interest. What object could there be in stopping a burrow now useless,
since it no longer contained prey and egg, and which will remain
useless, since the Sphex will not return to it? One can only explain
this irrational proceeding by regarding it as the necessary consequence
of preceding actions. In the normal state of things the Sphex hunts her
prey, lays an egg, and closes the hole. The prey has been caught, the
egg laid, and now comes the closing of the burrow, and the insect
closes it without reflecting at all, or guessing the fruitlessness of
her labour.
Third experiment.—To know all and nothing, according as the conditions
are normal or otherwise, is the strange antithesis presented by the
insect. Other examples drawn from the Sphegidæ will confirm us in this
proposition. Sphex albisecta attacks middle-sized Acridians, the
various species scattered in the neighbourhood of her burrow all
furnishing a tribute. From the abundance of these Acrididæ the chase is
carried on near at hand. When the vertical well-like burrow is ready,
the Sphex merely flies over the ground near, and espies an Acridian
feeding in the sunshine. To pounce and sting while it struggles is done
in a moment. After some fluttering of the wings, which unfold like
carmine or azure fans, some moving of feet up and down, the victim
becomes motionless. Next it must be got home by the Sphex on foot. She
performs this toilsome operation as do her kindred, dragging her game
between her feet, and holding one of the antennæ in her mandibles. If a
grass thicket has to be traversed, she hops and flutters from blade to
blade, keeping firm hold of her prey. When within a few feet of her
dwelling she executes the same manœuvre as does S. occitanica, but
without attaching the same importance to it, for sometimes she neglects
it. The game is left on the road, and though no apparent danger
threatens the dwelling, she hurries toward its mouth, and puts in her
head repeatedly, or even partly enters, then returns to the Acridian,
brings it nearer, and again leaves it to revisit her burrow, and so on
several times, always with eager haste.
These repeated visits have sometimes annoying results. The victim,
rashly abandoned on a slope, rolls to the bottom, and when the Sphex
returns and does not find it where she left it, she must hunt for it,
sometimes in vain. If found, there will be a difficult climb, which,
however, does not prevent her leaving it once more on the perilous
slope. The first of these repeated visits to her cell is easily
explained. Before bringing her heavy load she is anxious to make sure
that the entrance is clear, and that nothing will hinder her carrying
in the prey. But what is the use of her other visits, repeated so
speedily one after another? Are the Sphex’s ideas so unstable that she
forgets the one just made, and hurries back a moment later, only to
forget that she has done so, and so on? It would indeed be a slippery
memory where impressions vanished as soon as made. Let us leave this
too obscure question.
At length the game is brought to the edge of the well, its antennæ
hanging into the mouth, and there is an exact repetition of the method
used by S. flavipennis, and, though in less striking conditions, by S.
occitanica. She enters alone, reappears at the entrance, seizes the
antennæ, and drags in the Acridian. While she was within I have pushed
the prey rather farther off, and have always obtained precisely the
same result as in the case of the huntress of crickets. In both
Sphegidæ there was the same persistence in plunging into their burrows
before dragging down their prey. We must recollect that S. flavipennis
does not always allow herself to be duped by my trick of withdrawing
the insect. There are elect tribes among them,—strong-minded
families,—who after a while find out the tricks of the experimenter,
and know how to baffle them. But these revolutionaries capable of
progress are the few; the rest, rigid conservatives in manners and
customs, are the majority, the crowd. I cannot say whether the hunters
of Acrididæ show more or less cunning in different districts.
But the most remarkable thing, and the one to which I want specially to
come, is this. After withdrawing the prey of S. albisecta several times
from the mouth of the hole, and obliging her to fetch it back, I
profited by her descent to the bottom of her den to seize and put the
prey where she could not find it. She came up, sought about for a long
time, and, when quite convinced that it was not to be found, went down
again. A few moments later she reappeared. Was it to return to the
chase? Not the least in the world; she began to close the hole, and
with no temporary cover, such as a small flat stone to mark the
orifice, but with a solid mass of carefully collected dust and gravel
swept into the passage until it was quite filled. S. albisecta only
makes a single cell at the bottom of her well, and puts in but one
victim. This one specimen had been caught and dragged to the edge of
the hole, and if it was not stored, that was my fault, not her’s. The
Sphex worked by an inflexible rule, and according to that rule she
completed the work by stopping up the hole even if empty. Here we have
an exact repetition of the useless labour of S. occitanica whose
dwelling I rifled.
Fourth experiment.—It is almost impossible to be certain whether S.
flavipennis, which makes several calls at the bottom of the same
passage, and heaps several grasshoppers in each, commits the same
irrational mistakes when accidentally disturbed. A cell may be closed,
although empty or imperfectly stored, and yet the Sphex will return to
the same burrow to make others. Yet I have reason to believe that this
Sphex is subject to the same aberrations as her two relations. The
facts on which I base my belief are these. When the work is completed,
there are generally four grasshoppers in each cell, but it is not
uncommon to find three or only two. Four appears to me the usual
number—first, because it is the most frequent, and secondly, when I
have brought up young larvæ dug up when eating their first grasshopper,
I found that all, even those only provided with two or three, easily
finished those offered, up to four, but after that they hardly touched
the fifth ration. If four grasshoppers are required by the larva to
develop fully, why is it sometimes only provided with three or even
only two? Why this immense difference in the amount of food? It cannot
be from any difference in the joints served up, since all are
unmistakably of the same size, but must come from losing prey on the
road. In fact, one finds at the foot of the slopes whose upper parts
are occupied by Sphegidæ, grasshoppers killed, and then lost down the
incline, when, for some reason or other, the Sphex has momentarily left
them. These grasshoppers become the prey of ants and flies, and the
Sphex who finds them takes good care not to pick them up, as they would
take enemies into the burrow.
These facts seem to demonstrate that if S. flavipennis can compute
exactly how many victims to catch, she cannot attain to counting how
many reach their destination, as if the creature had no other guide as
to number than an irresistible impulse leading her to seek game a fixed
number of times. When this number of journeys has been made,—when the
Sphex has done all that is possible to store the captured prey,—her
work is done, and the cell is closed, whether completely provisioned or
not. Nature has endowed her with only those faculties called for under
ordinary circumstances by the interests of the larva, and these blind
faculties, unmodified by experience, being sufficient for the
preservation of the race, the animal cannot go farther.
I end then as I began: instinct knows everything in the unchanging
paths laid out for it; beyond them it is entirely ignorant. The sublime
inspirations of science, the astonishing inconsistencies of stupidity,
are both its portion, according as the creature acts under normal
conditions or under accidental ones.