Let us continue our series of experiments on Chalicodoma muraria. From
its position on a stone which one can move at will, its nest lends
itself to very interesting trials. This is the first of them. I change
the place of a nest by carrying the pebble it is placed on some couple
of yards away. Edifice and base forming but one, the move was made
without at all disturbing the cells. I set the pebble in an open place
well in sight, as it was before. When the bee returned, she could not
fail to see it.
After a few minutes the owner arrived and went straight where the nest
used to be. She hovered gently just above the vacant spot, looked, and
alighted just where the stone used to lie. There she walked about,
searching pertinaciously, then soared up and flew away. Her absence was
short; she came back speedily and resumed her search on foot or on the
wing—always on the spot formerly occupied by the nest. A new fit of
irritation expressed by a sudden flight through the osier bed, then as
sudden a return and resumption of the vain search—always over the
impression left by the pebble which I had carried away. These sudden
flights, prompt returns, and obstinate examinations of the empty place,
were repeated very many times before the mason bee could believe her
nest was gone. She certainly must have seen it in its new position, for
sometimes she flew only a few inches above it, but she did not care
about it. For her it only represented the nest of another bee.
Often the experiment ends without so much as a visit to the stone
carried three or four yards away; the bee departs and does not return.
If the distance be less—say a yard—sooner or later she alights on the
pebble on which her nest is built. She will visit the cell which she
was making or storing a little while earlier, plunge in her head
several times, examine the surface of the stone narrowly, and after
much hesitation return to search over the original spot. The nest,
which is no longer in its right place, is altogether abandoned, though
it be but a yard away. Vainly does the bee alight on it; she cannot
recognise it as hers. I convinced myself of this by finding it several
days later in just the same state as when I moved it. The cell, half
filled with honey, was still open, allowing the ants to pillage it; the
cell in process of construction was unfinished, without a single new
course of mortar. Of course the bee may have returned, but she had not
resumed her work. The displaced abode was abandoned for ever.
I shall not deduce the strange paradox that a bee, capable of returning
home from a great distance, is yet incapable of finding it a yard off;
the interpretation of the facts does not involve this. The conclusion
appears to be that she retains a tenacious impression of the spot
occupied by the nest, returning there with an indefatigable obstinacy
when the nest is gone. But of the nest itself she has a very vague
notion—does not recognise her own masonry kneaded with her own saliva,
nor the honey paste she had collected. Vainly does she visit her work,
the cell; she abandons it, not acknowledging it any more, since the
place where lies the pebble is no longer the same.
We must own that insect memory is a strange one, so lucid in general
knowledge of locality, so limited as to its home. I should be disposed
to name it topographical instinct; the creature knows the localities,
but not the dear nest—the dwelling. The Bembex led us to a like
conclusion. The nest being laid open, she cared nothing for the
family—for the larva writhing distressfully in the sun unrecognised.
What they do recognise, what they seek, and find with marvellous
precision, is the place where no longer exists anything of the entrance
door—not even a threshold.
If any doubt remain as to the powerlessness of Chalicodoma muraria to
know her nest except by the place which the pebble occupies on the
ground, this may set it at rest. I substituted a nest of one mason bee
for that of another, as alike as might be, both in masonry and storage.
Of course this exchange and those of which I shall speak later were
made during the absence of the owner. In the nest not hers, but placed
where her own had been, she established herself without hesitation. If
she had been building, I offered her a cell in process of construction,
and she worked on with the same care and zeal as if the work already
done had been her own. If she were bringing honey and pollen, I offered
a cell partly stored. Her journeys continued, with honey in her crop
and pollen underneath her body to complete filling the store of another
bee.
Thus the bee does not suspect the exchange, nor distinguish what is and
is not hers. She thinks she is continuing to work at a cell really her
own.
After leaving her for a time in possession of the exchanged nest, I
restored her own. The fresh change passed unobserved; her labour was
continued in the cell restored to her, at the point at which it had
arrived in the substituted one. Then I once more substituted the
strange nest, and still she persisted in her labour. Thus alternating
nests at the same spot, I thoroughly convinced myself that the insect
cannot perceive the difference between that which is her own and that
which is not. Whether the cell be hers or not, she works with equal
fervour, provided that the basis for the edifice—the stone—remains in
its original position.
One may lend a livelier interest to the experiment by using two
neighbouring nests—work at which is about equally advanced. I transpose
them, placing one where the other was; the distance is hardly a cubit.
Despite this close neighbourhood, which allows the bees to see both
nests at once and choose between them, the two bees on arriving each
immediately alighted on the substituted nest and went on working at it.
We may change the two nests at pleasure; we shall still see the two
mason bees keep to the spot chosen by them and work in turn—now at
their own cell, now at that of the other.
It may be thought that the confusion was caused by a close resemblance
between the two nests, since, at first little expecting the results
obtained, I began by choosing those as much alike as possible, lest the
bees should be repelled. My caution presupposed a clear-sightedness the
insect did not possess. I now took two nests exceedingly unlike, except
that in each the bee found a cell advanced in its work to the same
point. The first was an old nest, with the dome pierced with eight
holes, the orifices of cells of a preceding generation; one of these
had been restored, and the bee was storing it. The second was a new
nest, with no dome, and composed of a single cell with little stones on
the outside. Here too the bee was storing her paste. Certainly no two
nests could differ more: the one with its eight vacant rooms, and its
ample dome of clay, the other with a single cell—bare, and at most the
size of an acorn.
Well, the two mason bees did not hesitate long before the two exchanged
nests—hardly a yard apart. Each went to the site of its former abode.
The owner of the old nest found but a single cell. She rapidly
inspected the stone, and without further ceremony first plunged her
head into the cell to disgorge honey, and then her hind-quarters to
drop pollen. And this was no action performed to rid herself as soon as
possible of a trying burden, for she flew away and quickly returned
with fresh stores to be laid up. This bringing provisions to another’s
larder was repeated as often as I would allow. The other bee, finding,
instead of one cell a spacious building with eight chambers, was at
first considerably embarrassed. Which of the eight was the right
one?—in which was her heap of bee bread? She plunged down into each
room, and at length found what she was seeking—a condition like that
which she had left when she took her last journey, the beginning of a
store of food. From that moment she behaved like her neighbour, and
carried honey and pollen to a cell not made by her.
Let us restore the nests to their natural places, exchanging them
afresh. Each bee, after a little hesitation, sufficiently explained by
the very great difference between the two nests, will work alternately
in her own cell and the strange one. At length the egg is laid and the
cell closed, whichever the nest may be that she is occupied with at the
moment when the provisions are sufficient. Such facts show clearly why
I hesitate to give the name of memory to the singular faculty that
brings back the insect so accurately to the site of her nest, yet does
not allow her to distinguish her work from that of another, however
great may be the difference of appearance between them.
Now let us experiment on Chalicodoma muraria from another psychological
point of view. Here is a mason bee at work on the first course of her
cell; in exchange I give her one not only completed, but half full of
honey, which I stole from an owner who would speedily have laid an egg
there. What will the mason do with this munificent gift which spares
her the labour of building and storage? Leave her mortar, of course,
lay an egg, and close all up. Not at all! the animal finds our logic
illogical. The insect obeys an inevitable, unconscious impulse. It has
no choice as to what it shall do,—no discernment as to what is and is
not desirable,—but glides, as it were, down an irresistible slope
prepared for it beforehand to bring it to a determined end. The facts
still to be stated affirm this strongly.
The bee, which is building, and to which I offer a cell ready made and
full of honey, will not give up building for that; she is following her
trade as mason, and once on that tack, led on by unconscious impulse,
she must needs build, even if her labour be superfluous and contrary to
her interests. The cell I give her is certainly quite complete in the
opinion of its own constructor, since the bee from whom I subtracted it
was finishing the store of honey. To touch it up, and, above all, to
add to it is useless and absurd. All the same the bee which is building
will build. On the orifice of the honey store she lays another layer of
mortar, then another and another, until the cell is actually a third
beyond its usual height. Now the task is done—not as well indeed as if
the bee had continued the cell whose foundations she was laying when
the nests were exchanged, but certainly in a way more than enough to
demonstrate the irresistible impulse which drove the builder on. Then
came the storing, likewise abridged, for otherwise the honey would
overflow by the union of the stores of two bees. Thus the mason bee,
which is beginning to build, and to which one gives a cell completed
and filled with honey, alters nothing in the order of her work. First
she builds and then she stores; only she shortens her labours—instinct
warning her that the height of the cell and quantity of honey are
beginning to assume proportions too great.
The reverse of this is not less conclusive. To a mason bee which was
laying up food I would give a cell only just sketched out and unable to
receive the honey paste. This cell, still damp from the constructor’s
saliva, might or might not be accompanied by other cells, recently
closed and containing an egg and honey. The bee, whose half-filled cell
is thus replaced, seems greatly puzzled on arriving with her load at
this shallow hollow offering no place for the honey. She will examine
it, measure it with her eye, try it with her antennæ, and recognise its
insufficient depth. For a time she hesitates, departs, returns, flies
off again, and comes back in haste to dispose of her load. Her
embarrassment is visible; I could not help saying inwardly: “Take some
mortar—take some mortar, and finish your storehouse. It will only
require a few moments to make it deep enough.” The bee was of a
different opinion. She was laying in food, and food she must lay up,
happen what might. She could not decide to lay aside the pollen brush
for the mason’s trowel, and nothing could induce her to delay the
harvest which occupied her in order to take up that work of building
for which it is not the due moment. Rather would she seek another cell,
in the desired condition, and will penetrate there to store the honey,
even if received with fury by the owner. In fact, this happened. I
wished her success, knowing myself to be the cause of this desperate
act. My curiosity had turned an honest worker into a thief.
Matters may take a yet more serious turn, so obstinate and imperious is
the desire to harvest the store securely. The unfinished cell that the
bee refuses to accept instead of her own complete one, with its honey,
is sometimes, as I have said, among several containing paste and egg,
and newly closed. In this case I have seen, though not always, the
following sight. Having ascertained unmistakably that the unfinished
cell will not do, the bee begins to gnaw the cover of a neighbouring
one. With her saliva she softens a spot in the mortar, and patiently
digs away atom by atom in the hard covering. A long half hour passes
before the tiny dimple excavated is big enough to receive a pin’s head.
I waited. Then I got out of patience, and, feeling sure that she wanted
to open the storehouse, I decided to help her and shorten the labour.
With the point of my knife I knocked off the top; but the crown of the
cell came off too, and its edge was a good deal broken. In my
clumsiness I had made a graceful vase into a wretched, shattered pot. I
was right; the bee wanted to break open the door, and without troubling
herself as to the fragmentary state of the orifice, she immediately
established herself in the cell opened to her. Many times did she bring
honey and pollen, though the store was already complete. Finally, in
this cell containing an egg not hers she laid her own egg, and then
closed, as best she could, the shattered mouth. Thus this bee, who was
engaged in bringing food, neither could nor would be baffled by the
impossibility brought about by me of continuing her work unless she
completed the cell which replaced hers. What she was doing she
persisted in doing in spite of obstacles. She accomplished her task
thoroughly, but in the most absurd way,—by breaking into another bee’s
cell, continuing to store in a cell already overflowing, placing an egg
where the real owner had already laid one, and finally, closing an
orifice which needed serious repairs. Could one desire a better proof
of the irresistible impulse obeyed by the insect?
Finally, there are other rapid and consecutive actions so closely
connected that the execution of the second implies necessarily the
repetition of the first, even when this has become useless. I have
already said how Sphex flavipennis persists in going down into her
burrow alone, having brought near it the cricket which I cruelly
removed immediately. Her repeated discomfitures did not make her give
up the preliminary domiciliary visit, useless as it is when repeated
ten or twenty times. Chalicodoma muraria exhibits under another form a
like repetition of an act useless itself, but a necessary prelude to
the next one. Arrived with her booty, she goes through a double act of
storage. First she plunges head first into the cell to disgorge the
contents of her crop; then she comes out, returning at once backward to
brush off her load of pollen. At the moment when she is about to enter,
tail first, I gently put her aside with a straw, thus hindering her
second action. She begins all over again, going head first into the
cell, although her crop is empty. Then comes the turn of going in
backward. I instantly put her aside again, and again she goes in head
first. Once more I use my straw. And this goes on as long as the
observer pleases. Put aside just as she is about to introduce her
hinder parts into the cell, she returns to the orifice and persists in
descending head first. Sometimes she goes quite down—sometimes only
half-way, or perhaps there is a mere pretence at descending, and she
only stoops her head in the opening, but at any rate this quite useless
action—for the honey is already disgorged—invariably precedes the
entrance backward to deposit pollen. It is almost the movement of a
machine, not a wheel of which moves till the main one begins to turn.