VIEW THE MOBILE VERSION of www.bugsinsects.net Informational Site Network Informational
Privacy
   Home - Articles - Books

THE RED ANTS




The Pigeon transported for hundreds of miles is able to find his way
back to his Dove-cot; the Swallow, returning from his winter quarters
in Africa, crosses the sea and once more takes possession of the old
nest. What guides them on these long journeys? Is it sight? An
observer of supreme intelligence, one who, though surpassed by others
in the knowledge of the stuffed animal under a glass case, is almost
unrivalled in his knowledge of the live animal in its wild state,
Toussenel (Alphonse Toussenel (1803-1885), the author of a number of
interesting and valuable works on ornithology.--Translator's Note.),
the admirable writer of "L'Esprit des betes", speaks of sight and
meteorology as the Carrier-pigeon's guides:

'The French bird,' he says, 'knows by experience that the cold weather
comes from the north, the hot from the south, the dry from the east
and the wet from the west. That is enough meteorological knowledge to
tell him the cardinal points and to direct his flight. The Pigeon
taken in a closed basket from Brussels to Toulouse has certainly no
means of reading the map of the route with his eyes; but no one can
prevent him from feeling, by the warmth of the atmosphere, that he is
pursuing the road to the south. When restored to liberty at Toulouse,
he already knows that the direction which he must follow to regain his
Dove-cot is the direction of the north. Therefore he wings straight in
that direction and does not stop until he nears those latitudes where
the mean temperature is that of the zone which he inhabits. If he does
not find his home at the first onset, it is because he has borne a
little too much to the right or to the left. In any case, it takes him
but a few hours' search in an easterly or westerly direction to
correct his mistake.'

The explanation is a tempting one when the journey is taken north and
south; but it does not apply to a journey east and west, on the same
isothermal line. Besides, it has this defect, that it does not admit
of generalization. One cannot talk of sight and still less of the
influence of a change of climate when a Cat returns home, from one end
of a town to the other, threading his way through a labyrinth of
streets and alleys which he sees for the first time. Nor is it sight
that guides my Mason-bees, especially when they are let loose in the
thick of a wood. Their low flight, eight or nine feet above the
ground, does not allow them to take a panoramic view nor to gather the
lie of the land. What need have they of topography? Their hesitation
is short-lived: after describing a few narrow circles around the
experimenter, they start in the direction of the nest, despite the
cover of the forest, despite the screen of a tall chain of hills which
they cross by mounting the slope at no great height from the ground.
Sight enables them to avoid obstacles, without giving them a general
idea of their road. Nor has meteorology aught to do with the case: the
climate has not varied in those few miles of transit. My Mason-bees
have not learnt from any experience of heat, cold, dryness and damp:
an existence of a few weeks' duration does not allow of this. And,
even if they knew all about the four cardinal points, there is no
difference in climate between the spot where their nest lies and the
spot at which they are released; so that does not help them to settle
the direction in which they are to travel.

To explain these many mysteries, we are driven therefore to appeal to
yet another mystery, that is to say, a special sense denied to
mankind. Charles Darwin, whose weighty authority no one will gainsay,
arrives at the same conclusion. To ask if the animal be not impressed
by the terrestrial currents, to enquire if it be not influenced by the
close proximity of a magnetic needle: what is this but the recognition
of a magnetic sense? Do we possess a similar faculty? I am speaking,
of course, of the magnetism of the physicists and not of the magnetism
of the Mesmers and Cagliostros. Assuredly we possess nothing remotely
like it. What need would the mariner have of a compass, were he
himself a compass?

And this is what the great scientist acknowledges: a special sense, so
foreign to our organism that we are not able to form a conception of
it, guides the Pigeon, the Swallow, the Cat, the Mason-bee and a host
of others when away from home. Whether this sense be magnetic or no I
will not take upon myself to decide; I am content to have helped, in
no small degree, to establish its existence. A new sense added to our
number: what an acquisition, what a source of progress! Why are we
deprived of it? It would have been a fine weapon and of great service
in the struggle for life. If, as is contended, the whole of the animal
kingdom, including man, is derived from a single mould, the original
cell, and becomes self-evolved in the course of time, favouring the
best-endowed and leaving the less well-endowed to perish, how comes it
that this wonderful sense is the portion of a humble few and that it
has left no trace in man, the culminating achievement of the
zoological progression? Our precursors were very ill-advised to let so
magnificent an inheritance go: it was better worth keeping than a
vertebra of the coccyx or a hair of the moustache.

Does not the fact that this sense has not been handed down to us point
to a flaw in the pedigree? I submit the little problem to the
evolutionists; and I should much like to know what their protoplasm
and their nucleus have to say to it.

Is this unknown sense localized in a particular part of the Wasp and
the Bee? Is it exercised by means of a special organ? We immediately
think of the antennae. The antennae are what we always fall back upon
when the insect's actions are not quite clear to us; we gladly put
down to them whatever is most necessary to our arguments. For that
matter, I had plenty of fairly good reasons for suspecting them of
containing the sense of direction. When the Hairy Ammophila (A Sand-
wasp who hunts the Grey Worm, or Caterpillar of the Turnip-moth, to
serve as food for her grubs. For other varieties of the Ammophila, cf.
"Insect Life": chapter 15.--Translator's Note.) is searching for the
Grey Worm, it is with her antennae, those tiny fingers continually
fumbling at the soil, that she seems to recognize the presence of the
underground prey. Could not those inquisitive filaments, which seem to
guide the insect when hunting, also guide it when travelling? This
remained to be seen; and I did see.

I took some Mason-bees and amputated their antennae with the scissors,
as closely as I could. These maimed ones were then carried to a
distance and released. They returned to the nest with as little
difficulty as the others. I once experimented in the same way with the
largest of our Cerceres (Cerceris tuberculata) (Another Hunting Wasp,
who feeds her young on Weevils. Cf. "Insect Life": chapters 4 and 5.--
Translator's Note.); and the Weevil-huntress returned to her
galleries. This rids us of one hypothesis: the sense of direction is
not exercised by the antennae. Then where is its seat? I do not know.

What I do know is that the Mason-bees without antennae, though they go
back to the cells, do not resume work. They persist in flying in front
of their masonry, they alight on the clay cup, they perch on the rim
of the cell and there, seemingly pensive and forlorn, stand for a long
time contemplating the work which will never be finished; they go off,
they come back, they drive away any importunate neighbour, but they
fetch and carry no more honey or mortar. The next day, they do not
appear. Deprived of her tools, the worker loses all heart in her task.
When the Mason-bee is building, the antennae are constantly feeling,
fumbling and exploring, superintending, as it were, the finishing
touches given to the work. They are her instruments of precision; they
represent the builder's compasses, square, level and plumb-line.

Hitherto my experiments have been confined to the females, who are
much more faithful to the nest by virtue of their maternal
responsibilities. What would the males do if they were taken from
home? I have no great confidence in these swains who, for a few days,
form a tumultuous throng outside the nests, wait for the females to
emerge, quarrel for their possession, amid endless brawls, and then
disappear when the works are in full swing. What care they, I ask
myself, about returning to the natal nest rather than settling
elsewhere, provided that they find some recipient for their amatory
declarations? I was mistaken: the males do return to the nest. It is
true that, in view of their lack of strength, I did not subject them
to a long journey: about half a mile or so. Nevertheless, this
represented to them a distant expedition, an unknown country; for I do
not see them go on long excursions. By day, they visit the nests or
the flowers in the garden; at night, they take refuge in the old
galleries or in the interstices of the stone-heaps in the harmas.

The same nests are frequented by two Osmia-bees (Osmia tricornis and
Osmia Latreillii), who build their cells in the galleries left at
their disposal by the Chalicodomae. The most numerous is the first,
the Three-horned Osmia. It was a splendid opportunity to try and
discover to what extent the sense of direction may be regarded as
general in the Bees and Wasps; and I took advantage of it. Well, the
Osmiae (Osmia tricornis), both male and female, can find their way
back to the nest. My experiments were made very quickly, with small
numbers and over short distances; but the results agreed so closely
with the others that I was convinced. All told, the return to the
nest, including my earlier attempts, was verified in the case of four
species: the Chalicodoma of the Sheds, the Chalicodoma of the Walls,
the Three-horned Osmia and the Great or Warted Cerceris (Cerceris
tuberculata). ("Insect Life": chapter 19.--Translator's Note.) Shall I
generalize without reserve and allow all the Hymenoptera (The
Hymenoptera are an order of insects having four membranous wings and
include the Bees, Wasps, Ants, Saw-flies and Ichneumon-flies.--
Translator's Note.) this faculty of finding their way in unknown
country? I shall do nothing of the kind; for here, to my knowledge, is
a contradictory and very significant result.

Among the treasures of my harmas-laboratory, I place in the first rank
an Ant-hill of Polyergus rufescens, the celebrated Red Ant, the slave-
hunting Amazon. Unable to rear her family, incapable of seeking her
food, of taking it even when it is within her reach, she needs
servants who feed her and undertake the duties of housekeeping. The
Red Ants make a practice of stealing children to wait on the
community. They ransack the neighbouring Ant-hills, the home of a
different species; they carry away nymphs, which soon attain maturity
in the strange house and become willing and industrious servants.

When the hot weather of June and July sets in, I often see the Amazons
leave their barracks of an afternoon and start on an expedition. The
column measures five or six yards in length. If nothing worthy of
attention be met upon the road, the ranks are fairly well maintained;
but, at the first suspicion of an Ant-hill, the vanguard halts and
deploys in a swarming throng, which is increased by the others as they
come up hurriedly. Scouts are sent out; the Amazons recognize that
they are on a wrong track; and the column forms again. It resumes its
march, crosses the garden-paths, disappears from sight in the grass,
reappears farther on, threads its way through the heaps of dead
leaves, comes out again and continues its search. At last, a nest of
Black Ants is discovered. The Red Ants hasten down to the dormitories
where the nymphs lie and soon emerge with their booty. Then we have,
at the gates of the underground city, a bewildering scrimmage between
the defending blacks and the attacking reds. The struggle is too
unequal to remain indecisive. Victory falls to the reds, who race back
to their abode, each with her prize, a swaddled nymph, dangling from
her mandibles. The reader who is not acquainted with these slave-
raiding habits would be greatly interested in the story of the
Amazons. I relinquish it, with much regret: it would take us too far
from our subject, namely, the return to the nest.

The distance covered by the nymph-stealing column varies: it all
depends on whether Black Ants are plentiful in the neighbourhood. At
times, ten or twenty yards suffice; at others, it requires fifty, a
hundred or more. I once saw the expedition go beyond the garden. The
Amazons scaled the surrounding wall, which was thirteen feet high at
that point, climbed over it and went on a little farther, into a
cornfield. As for the route taken, this is a matter of indifference to
the marching column. Bare ground, thick grass, a heap of dead leaves
or stones, brickwork, a clump of shrubs: all are crossed without any
marked preference for one sort of road rather than another.

What is rigidly fixed is the path home, which follows the outward
track in all its windings and all its crossings, however difficult.
Laden with their plunder, the Red Ants return to the nest by the same
road, often an exceedingly complicated one, which the exigencies of
the chase compelled them to take originally. They repass each spot
which they passed at first; and this is to them a matter of such
imperative necessity that no additional fatigue nor even the gravest
danger can make them alter the track.

Let us suppose that they have crossed a thick heap of dead leaves,
representing to them a path beset with yawning gulfs, where every
moment some one falls, where many are exhausted as they struggle out
of the hollows and reach the heights by means of swaying bridges,
emerging at last from the labyrinth of lanes. No matter: on their
return, they will not fail, though weighed down with their burden,
once more to struggle through that weary maze. To avoid all this
fatigue, they would have but to swerve slightly from the original
path, for the good, smooth road is there, hardly a step away. This
little deviation never occurs to them.

I came upon them one day when they were on one of their raids. They
were marching along the inner edge of the stone-work of the garden-
pond, where I have replaced the old batrachians by a colony of Gold-
fish. The wind was blowing very hard from the north and, taking the
column in flank, sent whole rows of the Ants flying into the water.
The fish hurried up; they watched the performance and gobbled up the
drowning insects. It was a difficult bit; and the column was decimated
before it had passed. I expected to see the return journey made by
another road, which would wind round and avoid the fatal cliff. Not at
all. The nymph-laden band resumed the parlous path and the Goldfish
received a double windfall: the Ants and their prizes. Rather than
alter its track, the column was decimated a second time.

It is not easy to find the way home again after a distant expedition,
during which there have been various sorties, nearly always by
different paths; and this difficulty makes it absolutely necessary for
the Amazons to return by the same road by which they went. The insect
has no choice of route, if it would not be lost on the way: it must
come back by the track which it knows and which it has lately
travelled. The Processionary Caterpillars, when they leave their nest
and go to another branch, on another tree, in search of a type of leaf
more to their taste, carpet the course with silk and are able to
return home by following the threads stretched along their road. This
is the most elementary method open to the insect liable to stray on
its excursions: a silken path brings it home again. The
Processionaries, with their unsophisticated traffic-laws, are very
different from the Mason-bees and others, who have a special sense to
guide them.

The Amazon, though belonging to the Hymenopteron clan, herself
possesses rather limited homing-faculties, as witness her compulsory
return by her former trail. Can she imitate, to a certain extent, the
Processionaries' method, that is to say, does she leave, along the
road traversed, not a series of conducting threads, for she is not
equipped for that work, but some odorous emanation, for instance some
formic scent, which would allow her to guide herself by means of the
olfactory sense? This view is pretty generally accepted. The Ants,
people say, are guided by the sense of smell; and this sense of smell
appears to have its seat in the antennae, which we see in continual
palpitation. It is doubtless very reprehensible, but I must admit that
the theory does not inspire me with overwhelming enthusiasm. In the
first place, I have my suspicions about a sense of smell seated in the
antennae: I have given my reasons before; and, next, I hope to prove
by experiment that the Red Ants are not guided by a scent of any kind.

To lie in wait for my Amazons, for whole afternoons on end, often
unsuccessfully, meant taking up too much of my time. I engaged an
assistant whose hours were not so much occupied as mine. It was my
grand-daughter Lucie, a little rogue who liked to hear my stories of
the Ants. She had been present at the great battle between the reds
and blacks and was much impressed by the rape of the long-clothes
babies. Well-coached in her exalted functions, very proud of already
serving that august lady, Science, my little Lucie would wander about
the garden, when the weather seemed propitious, and keep an eye on the
Red Ants, having been commissioned to reconnoitre carefully the road
to the pillaged Ant-hill. She had given proof of her zeal; I could
rely upon it.

One day, while I was spinning out my daily quota of prose, there came
a banging at my study-door:

'It's I, Lucie! Come quick: the reds have gone into the blacks' house.
Come quick!'

'And do you know the road they took?'

'Yes, I marked it.'

'What! Marked it? How?'

'I did what Hop-o'-my-Thumb did: I scattered little white stones along
the road.'

I hurried out. Things had happened as my six-year-old colleague said.
Lucie had secured her provision of pebbles in advance and, on seeing
the Amazon regiment leave barracks, had followed them step by step and
placed her stones at intervals along the road covered. The Ants had
made their raid and were beginning to return along the track of tell-
tale pebbles. The distance to the nest was about a hundred paces,
which gave me time to make preparations for an experiment previously
contemplated.

I take a big broom and sweep the track for about a yard across. The
dusty particles on the surface are thus removed and replaced by
others. If they were tainted with any odorous effluvia, their absence
will throw the Ants off the track. I divide the road, in this way, at
four different points, a few feet a part.

The column arrives at the first section. The hesitation of the Ants is
evident. Some recede and then return, only to recede once more; others
wander along the edge of the cutting; others disperse sideways and
seem to be trying to skirt the unknown country. The head of the
column, at first closed up to a width of a foot or so, now scatters to
three or four yards. But fresh arrivals gather in their numbers before
the obstacle; they form a mighty array, an undecided horde. At last, a
few Ants venture into the swept zone and others follow, while a few
have meantime gone ahead and recovered the track by a circuitous
route. At the other cuttings, there are the same halts, the same
hesitations; nevertheless, they are crossed, either in a straight line
or by going round. In spite of my snares, the Ants manage to return to
the nest; and that by way of the little stones.

The result of the experiment seems to argue in favour of the sense of
smell. Four times over, there are manifest hesitations wherever the
road is swept. Though the return takes place, nevertheless, along the
original track, this may be due to the uneven work of the broom, which
has left certain particles of the scented dust in position. The Ants
who went round the cleared portion may have been guided by the
sweepings removed to either side. Before, therefore, pronouncing
judgment for or against the sense of smell, it were well to renew the
experiment under better conditions and to remove everything containing
a vestige of scent.

A few days later, when I have definitely decided on my plan, Lucie
resumes her watch and soon comes to tell me of a sortie. I was
counting on it, for the Amazons rarely miss an expedition during the
hot and sultry afternoons of June and July, especially when the
weather threatens storm. Hop-o'-my-Thumb's pebbles once more mark out
the road, on which I choose the point best-suited to my schemes.

A garden-hose is fixed to one of the feeders of the pond; the sluice
is opened; and the Ants' path is cut by a continuous torrent, two or
three feet wide and of unlimited length. The sheet of water flows
swiftly and plentifully at first, so as to wash the ground well and
remove anything that may possess a scent. This thorough washing lasts
for nearly a quarter of an hour. Then, when the Ants draw near,
returning from the plunder, I let the water flow more slowly and
reduce its depth, so as not to overtax the strength of the insects.
Now we have an obstacle which the Amazons must surmount, if it is
absolutely necessary for them to follow the first trail.

This time, the hesitation lasts long and the stragglers have time to
come up with the head of the column. Nevertheless, an attempt is made
to cross the torrent by means of a few bits of gravel projecting above
the water; then, failing to find bottom, the more reckless of the Ants
are swept off their feet and, without loosing hold of their prizes,
drift away, land on some shoal, regain the bank and renew their search
for a ford. A few straws borne on the waters stop and become so many
shaky bridges on which the Ants climb. Dry olive-leaves are converted
into rafts, each with its load of passengers. The more venturesome,
partly by their own efforts, partly by good luck, reach the opposite
bank without adventitious aid. I see some who, dragged by the current
to one or the other bank, two or three yards off, seem very much
concerned as to what they shall do next. Amid this disorder, amid the
dangers of drowning, not one lets go her booty. She would not dream of
doing so: death sooner than that! In a word, the torrent is crossed
somehow or other along the regular track.

The scent of the road cannot be the cause of this, it seems to me, for
the torrent not only washed the ground some time beforehand but also
pours fresh water on it all the time that the crossing is taking
place. Let us now see what will happen when the formic scent, if there
really be one on the trail, is replaced by another, much stronger
odour, one perceptible to our own sense of smell, which the first is
not, at least not under present conditions.

I wait for a third sortie and, at one point in the road taken by the
Ants, rub the ground with some handfuls of freshly gathered mint. I
cover the track, a little farther on, with the leaves of the same
plant. The Ants, on their return, cross the section over which the
mint was rubbed without apparently giving it a thought; they hesitate
in front of the section heaped up with leaves and then go straight on.

After these two experiments, first with the torrent of water which
washes away all traces of smell from the ground and then with the mint
which changes the smell, I think that we are no longer at liberty to
quote scent as the guide of the Ants that return to the nest by the
road which they took at starting. Further tests will tell us more
about it.

Without interfering with the soil, I now lay across the track some
large sheets of paper, newspapers, keeping them in position with a few
small stones. In front of this carpet, which completely alters the
appearance of the road, without removing any sort of scent that it may
possess, the Ants hesitate even longer than before any of my other
snares, including the torrent. They are compelled to make manifold
attempts, reconnaissances to right and left, forward movements and
repeated retreats, before venturing altogether into the unknown zone.
The paper straits are crossed at last and the march resumed as usual.

Another ambush awaits the Amazons some distance farther on. I have
divided the track by a thin layer of yellow sand, the ground itself
being grey. This change of colour alone is enough for a moment to
disconcert the Ants, who again hesitate in the same way, though not
for so long, as they did before the paper. Eventually, this obstacle
is overcome like the others.

As neither the stretch of sand nor the stretch of paper got rid of any
scented effluvia with which the trail may have been impregnated, it is
patent that, as the Ants hesitated and stopped in the same way as
before, they find their way not by sense of smell, but really and
truly by sense of sight; for, every time that I alter the appearance
of the track in any way whatever--whether by my destructive broom, my
streaming water, my green mint, my paper carpet or my golden sand--the
returning column calls a halt, hesitates and attempts to account for
the changes that have taken place. Yes, it is sight, but a very dull
sight, whose horizon is altered by the shifting of a few bits of
gravel. To this short sight, a strip of paper, a bed of mint-leaves, a
layer of yellow sand, a stream of water, a furrow made by the broom,
or even lesser modifications are enough to transform the landscape;
and the regiment, eager to reach home as fast as it can with its loot,
halts uneasily on beholding this unfamiliar scenery. If the doubtful
zones are at length passed, it is due to the fact that fresh attempts
are constantly being made to cross the doctored strips and that at
last a few Ants recognize well-known spots beyond them. The others,
relying on their clearer-sighted sisters, follow.

Sight would not be enough, if the Amazon had not also at her service a
correct memory for places. The memory of an Ant! What can that be? In
what does it resemble ours? I have no answers to these questions; but
a few words will enable me to prove that the insect has a very exact
and persistent recollection of places which it has once visited. Here
is something which I have often witnessed. It sometimes happens that
the plundered Ant-hill offers the Amazons a richer spoil than the
invading column is able to carry away. Or, again, the region visited
is rich in Ant-hills. Another raid is necessary, to exploit the site
thoroughly. In such cases, a second expedition takes place, sometimes
on the next day, sometimes two or three days later. This time, the
column does no reconnoitring on the way: it goes straight to the spot
known to abound in nymphs and travels by the identical path which it
followed before. It has sometimes happened that I have marked with
small stones, for a distance of twenty yards, the road pursued a
couple of days earlier and have then found the Amazons proceeding by
the same route, stone by stone:

'They will go first here and then there,' I said, according to the
position of the guide-stones.

And they would, in fact, go first here and then there, skirting my
line of pebbles, without any noticeable deviation.

Can one believe that odoriferous emanations diffused along the route
are going to last for several days? No one would dare to suggest it.
It must, therefore, be sight that directs the Amazons, sight assisted
by a memory for places. And this memory is tenacious enough to retain
the impression until the next day and later; it is scrupulously
faithful, for it guides the column by the same path as on the day
before, across the thousand irregularities of the ground.

How will the Amazon behave when the locality is unknown to her? Apart
from topographical memory, which cannot serve her here, the region in
which I imagine her being still unexplored, does the Ant possess the
Mason-bee's sense of direction, at least within modest limits, and is
she able thus to regain her Ant-hill or her marching column?

The different parts of the garden are not all visited by the marauding
legions to the same extent: the north side is exploited by preference,
doubtless because the forays in that direction are more productive.
The Amazons, therefore, generally direct their troops north of their
barracks; I seldom see them in the south. This part of the garden is,
if not wholly unknown, at least much less familiar to them than the
other. Having said that, let us observe the conduct of the strayed
Ant.

I take up my position near the Ant-hill; and, when the column returns
from the slave-raid, I force an Ant to step on a leaf which I hold out
to her. Without touching her, I carry her two or three paces away from
her regiment: no more than that, but in a southerly direction. It is
enough to put her astray, to make her lose her bearings entirely. I
see the Amazon, now replaced on the ground, wander about at random,
still, I need hardly say, with her booty in her mandibles; I see her
hurry away from her comrades, thinking that she is rejoining them; I
see her retrace her steps, turn aside again, try to the right, try to
the left and grope in a host of directions, without succeeding in
finding her whereabouts. The pugnacious, strong-jawed slave-hunter is
utterly lost two steps away from her party. I have in mind certain
strays who, after half an hour's searching, had not succeeded in
recovering the route and were going farther and farther from it, still
carrying the nymph in their teeth. What became of them? What did they
do with their spoil? I had not the patience to follow those dull-
witted marauders to the end.

Let us repeat the experiment, but place the Amazon to the north. After
more or less prolonged hesitations, after a search now in this
direction, now in that, the Ant succeeds in finding her column. She
knows the locality.

Here, of a surety, is a Hymenopteron deprived of that sense of
direction which other Hymenoptera enjoy. She has in her favour a
memory for places and nothing more. A deviation amounting to two or
three of our strides is enough to make her lose her way and to keep
her from returning to her people, whereas miles across unknown country
will not foil the Mason-bee. I expressed my surprise, just now, that
man was deprived of a wonderful sense wherewith certain animals are
endowed. The enormous distance between the two things compared might
furnish matter for discussion. In the present case, the distance no
longer exists: we have to do with two insects very near akin, two
Hymenoptera. Why, if they issue from the same mould, has one a sense
which the other has not, an additional sense, constituting a much more
overpowering factor than the structural details? I will wait until the
evolutionists condescend to give me a valid reason.

To return to this memory for places whose tenacity and fidelity I have
just recognized: to what degree does it consent to retain impressions?
Does the Amazon require repeated journeys in order to learn her
geography, or is a single expedition enough for her? Are the line
followed and the places visited engraved on her memory from the first?
The Red Ant does not lend herself to the tests that might furnish the
reply: the experimenter is unable to decide whether the path followed
by the expeditionary column is being covered for the first time, nor
is it in his power to compel the legion to adopt this or that
different road. When the Amazons go out to plunder the Ant-hills, they
take the direction which they please; and we are not allowed to
interfere with their march. Let us turn to other Hymenoptera for
information.

I select the Pompili, whose habits we shall study in detail in a later
chapter. (For the Wasp known as the Pompilus, or Ringed Calicurgus,
cf. "The Life and Love of the Insect", by J. Henri Fabre, translated
by Alexander Teixeira de Mattos: chapter 12.--Translator's Note.) They
are hunters of Spiders and diggers of burrows. The game, the food of
the coming larva, is first caught and paralysed; the home is excavated
afterwards. As the heavy prey would be a grave encumbrance to the Wasp
in search of a convenient site, the Spider is placed high up, on a
tuft of grass or brushwood, out of the reach of marauders, especially
Ants, who might damage the precious morsel in the lawful owner's
absence. After fixing her booty on the verdant pinnacle, the Pompilus
casts around for a favourable spot and digs her burrow. During the
process of excavation, she returns from time to time to her Spider;
she nibbles at the prize, feels, touches it here and there, as though
taking stock of its plumpness and congratulating herself on the
plentiful provender; then she returns to her burrow and goes on
digging. Should anything alarm or distress her, she does not merely
inspect her Spider: she also brings her a little closer to her work-
yard, but never fails to lay her on the top of a tuft of verdure.
These are the manoeuvres of which I can avail myself to gauge the
elasticity of the Wasp's memory.

While the Pompilus is at work on the burrow, I seize the prey and
place it in an exposed spot, half a yard away from its original
position. The Pompilus soon leaves the hole to enquire after her booty
and goes straight to the spot where she left it. This sureness of
direction, this faithful memory for places can be explained by
repeated previous visits. I know nothing of what has happened
beforehand. Let us take no notice of this first expedition; the others
will be more conclusive. For the moment, the Pompilus, without the
least hesitation, finds the tuft of grass whereon her prey was lying.
Then come marches and counter-marches upon that tuft, minute
explorations and frequent returns to the exact spot where the Spider
was deposited. At last, convinced that the prize is no longer there,
the Wasp makes a leisurely survey of the neighbourhood, feeling the
ground with her antennae as she goes. The Spider is descried in the
exposed spot where I had placed her. Surprise on the part of the
Pompilus, who goes forward and then suddenly steps back with a start:

'Is it alive?' she seems to ask. 'Is it dead? Is it really my Spider?
Let us be wary!'

The hesitation does not last long: the huntress grabs her victim,
drags her backwards and places her, still high up, on a second tuft of
herbage, two or three steps away from the first. She then goes back to
the burrow and digs for a while. For the second time, I remove the
Spider and lay her at some distance, on the bare ground. This is the
moment to judge of the Wasp's memory. Two tufts of grass have served
as temporary resting-places for the game. The first, to which she
returned with such precision, the Wasp may have learnt to know by a
more or less thorough examination, by reiterated visits that escaped
my eye; but the second has certainly made but a slight impression on
her memory. She adopted it without any studied choice; she stopped
there just long enough to hoist her Spider to the top; she saw it for
the first time and saw it hurriedly, in passing. Is that rapid glance
enough to provide an exact recollection? Besides, there are now two
localities to be modelled in the insect's memory: the first shelf may
easily be confused with the second. To which will the Pompilus go?

We shall soon find out: here she comes, leaving the burrow to pay a
fresh visit to the Spider. She runs straight to the second tuft, where
she hunts about for a long time for her absent prey. She knows that it
was there, when last seen, and not elsewhere; she persists in looking
for it there and does not once think of going back to the first perch.
The first tuft of grass no longer counts; the second alone interests
her. And then the search in the neighbourhood begins again.

On finding her game on the bare spot where I myself have placed it,
the Pompilus quickly deposits the Spider on a third tuft of grass; and
the experiment is renewed. This time, the Pompilus hurries to the
third tuft when she comes to look after her Spider; she hurries to it
without hesitation, without confusing it in any way with the first
two, which she scorns to visit, so sure is her memory. I do the same
thing a couple of times more; and the insect always returns to the
last perch, without worrying about the others. I stand amazed at the
memory of that pigmy. She need but catch a single hurried glimpse of a
spot that differs in no wise from a host of others in order to
remember it quite well, notwithstanding the fact that, as a miner
relentlessly pursuing her underground labours, she has other matters
to occupy her mind. Could our own memory always vie with hers? It is
very doubtful. Allow the Red Ant the same sort of memory; and her
peregrinations, her returns to the nest by the same road are no longer
difficult to explain.

Tests of this kind have furnished me with some other results worthy of
mention. When convinced, by untiring explorations, that her prey is no
longer on the tuft where she laid it, the Pompilus, as we were saying,
looks for it in the neighbourhood and finds it pretty easily, for I am
careful to put it in an exposed place. Let us increase the difficulty
to some extent. I dig the tip of my finger into the ground and lay the
Spider in the little hole thus obtained, covering her with a tiny
leaf. Now the Wasp, while in quest of her lost prey, happens to walk
over this leaf, to pass it again and again without suspecting that the
Spider lies beneath, for she goes and continues her vain search
farther off. Her guide, therefore is not scent, but sight.
Nevertheless, she is constantly feeling the ground with her antennae.
What can be the function of those organs? I do not know, although I
assert that they are not olfactory organs. The Ammophila, in search of
her Grey Worm, had already led me to make the same assertion; I now
obtain an experimental proof which seems to me decisive. I would add
that the Pompilus has very short sight: often she passes within a
couple of inches of her Spider without seeing her.





Next: SOME REFLECTIONS UPON INSECT PSYCHOLOGY

Previous: THE STORY OF MY CATS



Add to del.icio.us Add to Reddit Add to Digg Add to Del.icio.us Add to Google Add to Twitter Add to Stumble Upon
Add to Informational Site Network
Report
Privacy
SHAREADD TO EBOOK