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EXCHANGING THE NESTS




Let us continue our series of tests with the Mason-bee of the Walls.
Thanks to its position on a pebble which we can move at will, the nest
of this Bee lends itself to most interesting experiments. Here is the
first: I shift a nest from its place, that is to say, I carry the
pebble which serves as its support to a spot two yards away. As the
edifice and its base form but one, the removal is performed without
the smallest disturbance of the cells. I lay the boulder in an exposed
place where it is well in view, as it was on its original site. The
Bee returning from her harvest cannot fail to see it.

In a few minutes, the owner arrives and goes straight to where the
nest stood. She hovers gracefully over the vacant site, examines and
alights upon the exact spot where the stone used to lie. Here she
walks about for a long time, making persistent searches; then the Bee
takes wing and flies away to some distance. Her absence is of short
duration. Here she is back again. The search is resumed, walking and
flying, and always on the site which the nest occupied at first. A
fresh fit of exasperation, that is to say, an abrupt flight across the
osier-bed, is followed by a fresh return and a renewal of the vain
search, always upon the mark left by the shifted pebble. These sudden
departures, these prompt returns, these persevering inspections of the
deserted spot continue for a long time, a very long time, before the
Mason is convinced that her nest is gone. She has certainly seen it,
has seen it over and over again in its new position, for sometimes she
has flown only a few inches above it; but she takes no notice of it.
To her, it is not her nest, but the property of another Bee.

Often the experiment ends without so much as a single visit to the
boulder which I have moved two or three yards away: the Bee goes off
and does not return. If the distance be less, a yard for instance, the
Mason sooner or later alights on the stone which supports her abode.
She inspects the cell which she was building or provisioning a little
while before, repeatedly dips her head into it, examines the surface
of the pebble step by step and, after long hesitations, goes and
resumes her search on the site where the home ought to be. The nest
that is no longer in its natural place is definitely abandoned, even
though it be but a yard away from the original spot. Vainly does the
Bee settle on it time after time: she cannot recognize it as hers. I
was convinced of this on finding it, several days after the
experiment, in just the same condition as when I moved it. The open
cell half-filled with honey was still open and was surrendering its
contents to the pillaging Ants; the cell that was building had
remained unfinished, with not a single layer added to it. The Bee,
obviously, may have returned to it; but she had not resumed work upon
it. The transplanted dwelling was abandoned for good and all.

I will not deduce the strange paradox that the Mason-bee, though
capable of finding her nest from the verge of the horizon, is
incapable of finding it at a yard's distance: I interpret the
occurrence as meaning something quite different. The proper inference
appears to me to be this: the Bee retains a rooted impression of the
site occupied by the nest and returns to it with unwearying
persistence even when the nest is gone. But she has only a very vague
notion of the nest itself. She does not recognize the masonry which
she herself has erected and kneaded with her saliva; she does not know
the pollen-paste which she herself has stored. In vain she inspects
her cell, her own handiwork; she abandons it, refusing to acknowledge
it as hers, once the spot whereon the pebble rests is changed.

Insect memory, it must be confessed, is a strange one, displaying such
lucidity in its general acquaintance with locality and such
limitations in its knowledge of the dwelling. I feel inclined to call
it topographical instinct: it grasps the map of the country and not
the beloved nest, the home itself. The Bembex-wasps (Cf. "Insect
Life": chapters 16 to 19.--Translator's Note.) have already led us to
a like conclusion. When the nest is laid open, these Wasps become
wholly indifferent to the family, to the grub writhing in agony in the
sun. They do not recognize it. What they do recognize, what they seek
and find with marvellous precision, is the site of the entrance-door
of which nothing at all is left, not even the threshold.

If any doubts remained as to the incapacity of the Mason-bee of the
Walls to know her nest other than by the place which the pebble
occupies on the ground, here is something to remove them: for the nest
of one Mason-bee, I substitute that of another, resembling it as
closely as possible in respect to both masonry and storage. This
exchange and those of which I shall speak presently are of course made
in the owner's absence. The Bee settles without hesitation in this
nest which is not hers, but which stands where the other did. If she
was building, I offer her a cell in process of building. She continues
the masonry with the same care and the same zeal as if the work
already done were her own work. If she was fetching honey and pollen,
I offer her a partly-provisioned cell. She continues her journeys,
with honey in her crop and pollen under her belly, to finish filling
another's warehouse. The Bee, therefore, does not suspect the
exchange; she does not distinguish between what is her property and
what is not; she imagines that she is still working at the cell which
is really hers.

After leaving her for a time in possession of the strange nest, I give
her back her own. This fresh change passes unperceived by the Bee: the
work is continued in the cell restored to her at the point which it
had reached in the substituted cell. I once more replace it by the
strange nest; and again the insect persists in continuing its labour.
By thus constantly interchanging the strange nest and the proper nest,
without altering the actual site, I thoroughly convinced myself of the
Bee's inability to discriminate between what is her work and what is
not. Whether the cell belong to her or to another, she labours at it
with equal zest, so long as the basis of the edifice, the pebble,
continues to occupy its original position.

The experiment receives an added interest if we employ two
neighbouring nests the work on which is about equally advanced. I move
each to where the other stood. They are not much more than thirty
inches a part. In spite of their being so near to each other that it
is quite possible for the insects to see both homes at once and choose
between them, each Bee, on arriving, settles immediately on the
substituted nest and continues her work there. Change the two nests as
often as you please and you shall see the two Mason-bees keep to the
site which they selected and labour in turn now at their own cell and
now at the other's.

One might think that the cause of this confusion lies in a close
resemblance between the two nests, for at the start, little expecting
the results which I was to obtain, I used to choose the nests which I
interchanged as much alike as possible, for fear of disheartening the
Bees. I need not have taken this precaution: I was giving the insect
credit for a perspicacity which it does not possess. Indeed, I now
take two nests which are extremely unlike each other, the only point
of resemblance being that, in each case, the toiler finds a cell in
which she can continue the work which she is actually doing. The first
is an old nest whose dome is perforated with eight holes, the
apertures of the cells of the previous generation. One of these cells
has been repaired; and the Bee is busy storing it. The second is a
nest of recent construction, which has not received its mortar dome
and consists of a single cell with its stucco covering. Here too the
insect is busy hoarding pollen-paste. No two nests could present
greater differences: one with its eight empty chambers and its
spreading clay dome; the other with its single bare cell, at most the
size of an acorn.

Well, the two Mason-bees do not hesitate long in front of these
exchanged nests, not three feet away from each other. Each makes for
the site of her late home. One, the original owner of the old nest,
finds nothing but a solitary cell. She rapidly inspects the pebble
and, without further formalities, first plunges her head into the
strange cell, to disgorge honey, and then her abdomen, to deposit
pollen. And this is not an action due to the imperative need of
ridding herself as quickly as possible, no matter where, of an irksome
load, for the Bee flies off and soon comes back again with a fresh
supply of provender, which she stores away carefully. This carrying of
provisions to another's larder is repeated as often as I permit it.
The other Bee, finding instead of her one cell a roomy structure
consisting of eight apartments, is at first not a little embarrassed.
Which of the eight cells is the right one? In which is the heap of
paste on which she had begun? The Bee therefore visits the chambers
one by one, dives right down to the bottom and ends by finding what
she seeks, that is to say, what was in her nest when she started on
her last journey, the nucleus of a store of food. Thenceforward she
behaves like her neighbour and goes on carrying honey and pollen to
the warehouse which is not of her constructing.

Restore the nests to their original places, exchange them yet once
again and both Bees, after a short hesitation which the great
difference between the two nests is enough to explain, will pursue the
work in the cell of her own making and in the strange cell
alternately. At last the egg is laid and the sanctuary closed, no
matter what nest happens to be occupied at the moment when the
provisioning reaches completion. These incidents are sufficient to
show why I hesitate to give the name of memory to the singular faculty
that brings the insect back to her nest with such unerring precision
and yet does not allow her to distinguish her work from some one
else's, however great the difference may be.

We will now experiment with Chalicodoma muraria from another
psychological point of view. Here is a Mason-bee building; she is at
work on the first course of her cell. I give her in exchange a cell
not only finished as a structure, but also filled nearly to the top
with honey. I have just stolen it from its owner, who would not have
been long before laying her egg in it. What will the Mason do in the
presence of this munificent gift, which saves her the trouble of
building and harvesting? She will leave the mortar no doubt, finish
storing the Bee-bread, lay her egg and seal up. A mistake, an utter
mistake: our logic is not the logic of the insect, which obeys an
inevitable, unconscious prompting. It has no choice as to what it
shall do; it cannot discriminate between what is and what is not
advisable; it glides, as it were, down an irresistible slope prepared
beforehand to bring it to a definite end. This is what the facts that
still remain to be stated proclaim with no uncertain voice.

The Bee who was building and to whom I offer a cell ready-built and
full of honey does not lay aside her mortar for that. She was doing
mason's work; and, once on that tack, guided by the unconscious
impulse, she has to keep masoning, even though her labour be useless,
superfluous and opposed to her interests. The cell which I give her is
certainly perfect, looked upon as a building, in the opinion of the
master-builder herself, since the Bee from whom I took it was
completing the provision of honey. To touch it up, especially to add
to it, is useless and, what is more, absurd. No matter: the Bee who
was masoning will mason. On the aperture of the honey-store she lays a
first course of mortar, followed by another and yet another, until at
last the cell is a third taller then the regulation height. The
masonry-task is now done, not as perfectly, it is true, as if the Bee
had gone on with the cell whose foundations she was laying at the
moment when I exchanged the nests, but still to an extent which is
more than enough to prove the overpowering impulse which the builder
obeys. Next comes the victualling, which is also cut short, lest the
honey-store swelled by the joint contributions of the two Bees should
overflow. Thus the Mason-bee who is beginning to build and to whom we
give a complete cell, a cell filled with honey, makes no change in the
order of her work: she builds first and then victuals. Only she
shortens her work, her instinct warning her that the height of the
cell and the quantity of honey are beginning to assume extravagant
proportions.

The converse is equally conclusive. To a Mason-bee engaged in
victualling I give a nest with a cell only just begun and not at all
fit to receive the paste. This cell, with its last course still wet
with its builder's saliva, may or may not be accompanied by other
cells recently closed up, each with its honey and its egg. The Bee,
finding this in the place of her half-filled honey-store, is greatly
perplexed what to do when she comes with her harvest to this
unfinished, shallow cup, in which there is no place to put the honey.
She inspects it, measures it with her eyes, tries it with her antennae
and recognizes its insufficient capacity. She hesitates for a long
time, goes away, comes back, flies away again and soon returns, eager
to deposit her treasure. The insect's embarrassment is most evident;
and I cannot help saying, inwardly:

'Get some mortar, get some mortar and finish making the warehouse. It
will only take you a few moments; and you will have a cupboard of the
right depth.'

The Bee thinks differently: she was storing her cell and she must go
on storing, come what may. Never will she bring herself to lay aside
the pollen-brush for the trowel; never will she suspend the foraging
which is occupying her at this moment to begin the work of
construction which is not yet due. She will rather go in search of a
strange cell, in the desired condition, and slip in there to deposit
her honey, at the risk of meeting with a warm reception from the irate
owner. She goes off, in fact, to try her luck. I wish her success,
being myself the cause of this desperate act. My curiosity has turned
an honest worker into a robber.

Things may take a still more serious turn, so invincible, so imperious
is the desire to have the booty stored in a safe place without delay.
The uncompleted cell which the Bee refuses to accept instead of her
own finished warehouse, half-filled with honey, is often, as I said,
accompanied by other cells, not long closed, each containing its Bee-
bread and its egg. In this case, I have sometimes, though not always,
witnessed the following: when once the Bee realises the shortcomings
of the unfinished nest, she begins to gnaw the clay lid closing one of
the adjoining cells. She softens a part of the mortar cover with
saliva and patiently, atom by atom, digs through the hard wall. It is
very slow work. A good half-hour elapses before the tiny cavity is
large enough to admit a pin's head. I wait longer still. Then I lose
patience; and, fully convinced that the Bee is trying to open the
store-room, I decide to help her to shorten the work. The upper part
of the cell comes away with it, leaving the edges badly broken. In my
awkwardness, I have turned an elegant vase into a wretched cracked
pot.

I was right in my conjecture: the Bee's intention was to break open
the door. Straight away, without heeding the raggedness of the
orifice, she settles down in the cell which I have opened for her.
Time after time, she fetches honey and pollen, though the larder is
already fully stocked. Lastly, she lays her egg in this cell which
already contains an egg that is not hers, having done which she closes
the broken aperture to the best of her ability. So this purveyor had
neither the knowledge nor the power to bow to the inevitable. I had
made it impossible for her to go on with her purveying, unless she
first completed the unfinished cell substituted for her own. But she
did not retreat before that impossible task. She accomplished her
work, but in the absurdest way: by injuriously trespassing upon
another's property, by continuing to store provisions in a cupboard
already full to overflowing, by laying her egg in a cell in which the
real owner had already laid and lastly by hurriedly closing an orifice
that called for serious repairs. What better proof could be wished of
the irresistible propensity which the insect obeys?

Lastly, there are certain swift and consecutive actions so closely
interlinked that the performance of the second demands a previous
repetition of the first, even when this action has become useless. I
have already described how the Yellow-winged Sphex (Cf. "Insect Life":
chapters 6 to 9.--Translator's Note.) persists in descending into her
burrow alone, after depositing at its edge the Cricket whom I
maliciously at once remove. Her repeated discomfitures do not make her
abandon the preliminary inspection of the home, an inspection which
becomes quite useless when renewed for the tenth or twentieth time.
The Mason-bee of the Walls shows us, under another form, a similar
repetition of an act which is useless in itself, but which is the
compulsory preface to the act that follows. When arriving with her
provisions, the Bee performs a twofold operation of storing. First,
she dives head foremost into the cell, to disgorge the contents of her
crop; next, she comes out and at once goes in again backwards, to
brush her abdomen and rub off the load of pollen. At the moment when
the insect is about to enter the cell tail first, I push her aside
gently with a straw. The second act is thus prevented. The Bee now
begins the whole performance over again, that is to say, she once more
dives head first to the bottom of the cell, though she has nothing
left to disgorge, as her crop has just been emptied. When this is
done, it is the belly's turn. I instantly push her aside again. The
insect repeats its proceedings, still entering head first; I also
repeat my touch of the straw. And this can go on as long as the
observer pleases. Pushed aside at the moment when she is about to
insert her abdomen into the cell, the Bee goes back to the opening and
persists in going down head first to begin with. Sometimes, she
descends to the bottom, sometimes only half-way, sometimes again she
only pretends to descend, just bending her head into the aperture;
but, whether completed or not, this action, for which there is no
longer any motive, since the honey has already been disgorged,
invariably precedes the entrance backwards to deposit the pollen. It
is almost the movement of a machine whose works are only set going
when the driving-wheel begins to revolve.





Next: MORE ENQUIRIES INTO MASON-BEES

Previous: EXPERIMENTS



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