Bramble-bees and Others
by
J. Henri Fabre
Part 1 out of 5
This etext was produced by Sue Asscher
BRAMBLE-BEES AND OTHERS
by J. HENRI FABRE
TRANSLATED BY ALEXANDER TEIXEIRA DE MATTOS, F.Z.S.
TRANSLATOR'S NOTE.
In this volume I have collected all the essays on Wild Bees scattered
through the "Souvenirs entomologiques," with the exception of those
on the Chalicodomae, or Mason-bees proper, which form the contents of
a separate volume entitled "The Mason-bees."
The first two essays on the Halicti (Chapters 12 and 13) have already
appeared in an abbreviated form in "The Life and Love of the Insect,"
translated by myself and published by Messrs. A. & C. Black (in
America by the Macmillan Co.) in 1911. With the greatest courtesy and
kindness, Messrs. Black have given me their permission to include
these two chapters in the present volume; they did so without fee or
consideration of any kind, merely on my representation that it would
be a great pity if this uniform edition of Fabre's Works should be
rendered incomplete because certain essays formed part of volumes of
extracts previously published in this country. Their generosity is
almost unparalleled in my experience; and I wish to thank them
publicly for it in the name of the author, of the French publishers
and of the English and American publishers, as well as in my own.
Of the remaining chapters, one or two have appeared in the "English
Review" or other magazines; but most of them now see the light in
English for the first time.
I have once more, as in the case of "The Mason-bees," to thank Miss
Frances Rodwell for the help which she has given me in the work of
translation and research; and I am also grateful for much kind
assistance received from the staff of the Natural History Museum and
from Mr. Geoffrey Meade-Waldo in particular.
ALEXANDER TEIXEIRA DE MATTOS.
Chelsea, 1915.
CONTENTS.
TRANSLATOR'S NOTE.
CHAPTER 1. BRAMBLE-DWELLERS.
CHAPTER 2. THE OSMIAE.
CHAPTER 3. THE DISTRIBUTION OF THE SEXES.
CHAPTER 4. THE MOTHER DECIDES THE SEX OF THE EGG.
CHAPTER 5. PERMUTATIONS OF SEX.
CHAPTER 6. INSTINCT AND DISCERNMENT.
CHAPTER 7. ECONOMY OF ENERGY.
CHAPTER 8. THE LEAF-CUTTERS.
CHAPTER 9. THE COTTON-BEES.
CHAPTER 10. THE RESIN-BEES.
CHAPTER 11. THE POISON OF THE BEE.
CHAPTER 12. THE HALICTI: A PARASITE.
CHAPTER 13. THE HALICTI: THE PORTRESS.
CHAPTER 14. THE HALICTI: PARTHENOGENESIS.
INDEX.
CHAPTER 1. BRAMBLE-DWELLERS.
The peasant, as he trims his hedge, whose riotous tangle threatens to
encroach upon the road, cuts the trailing stems of the bramble a foot
or two from the ground and leaves the root-stock, which soon dries
up. These bramble-stumps, sheltered and protected by the thorny
brushwood, are in great demand among a host of Hymenoptera who have
families to settle. The stump, when dry, offers to any one that knows
how to use it a hygienic dwelling, where there is no fear of damp
from the sap; its soft and abundant pith lends itself to easy work;
and the top offers a weak spot which makes it possible for the insect
to reach the vein of least resistance at once, without cutting away
through the hard ligneous wall. To many, therefore, of the Bee and
Wasp tribe, whether honey-gatherers or hunters, one of these dry
stalks is a valuable discovery when its diameter matches the size of
its would-be inhabitants; and it is also an interesting subject of
study to the entomologist who, in the winter, pruning-shears in hand,
can gather in the hedgerows a faggot rich in small industrial
wonders. Visiting the bramble-bushes has long been one of my
favourite pastimes during the enforced leisure of the wintertime; and
it is seldom but some new discovery, some unexpected fact, makes up
to me for my torn fingers.
My list, which is still far from being complete, already numbers
nearly thirty species of bramble-dwellers in the neighbourhood of my
house; other observers, more assiduous than I, exploring another
region and one covering a wider range, have counted as many as fifty.
I give at foot an inventory of the species which I have noted.
(Bramble-dwelling insects in the neighbourhood of Serignan
(Vaucluse):
1. MELLIFEROUS HYMENOPTERA.
Osmia tridentata, DUF. and PER.
Osmia detrita, PEREZ.
Anthidium scapulare, LATR.
Heriades rubicola, PEREZ.
Prosopis confusa, SCHENCK.
Ceratina chalcites, GERM.
Ceratina albilabris, FAB.
Ceratina callosa, FAB.
Ceratina coerulea, VILLERS.
2. HUNTING HYMENOPTERA.
Solenius vagus, FAB. (provisions, Diptera).
Solenius lapidarius, LEP. (provisions, Spiders?).
Cemonus unicolor, PANZ. (provisions, Plant-lice).
Psen atratus (provisions, Black Plant-lice).
Tripoxylon figulus, LIN. (provisions, Spiders).
A Pompilus, unknown (provisions, Spiders).
Odynerus delphinalis, GIRAUD.
3. PARASITICAL HYMENOPTERA.
A Leucopsis, unknown (parasite of Anthidium scapulare).
A small Scoliid, unknown (parasite of Solenius vagus).
Omalus auratus (parasite of various bramble-dwellers).
Cryptus bimaculatus, GRAV. (parasite of Osmia detrita).
Cryptus gyrator, DUF. (parasite of Tripoxylon figulus).
Ephialtes divinator, ROSSI (parasite of Cemonus unicolor).
Ephialtes mediator, GRAV. (parasite of Psen atratus).
Foenus pyrenaicus, GUERIN.
Euritoma rubicola, J. GIRAUD (parasite of Osmia detrita).
4. COLEOPTERA.
Zonitis mutica, FAB. (parasite of Osmia tridentata).
Most of these insects have been submitted to a learned expert,
Professor Jean Perez, of Bordeaux. I take this opportunity of
renewing my thanks for his kindness in identifying them for me.--
Author's Note.)
They include members of very diverse corporations. Some, more
industrious and equipped with better tools, remove the pith from the
dry stem and thus obtain a vertical cylindrical gallery, the length
of which may be nearly a cubit. This sheath is next divided, by
partitions, into more or less numerous storeys, each of which forms
the cell of a larva. Others, less well-endowed with strength and
implements, avail themselves of the old galleries of other insects,
galleries that have been abandoned after serving as a home for their
builder's family. Their only work is to make some slight repairs in
the ruined tenement, to clear the channel of its lumber, such as the
remains of cocoons and the litter of shattered ceilings, and lastly
to build new partitions, either with a plaster made of clay or with a
concrete formed of pith-scrapings cemented with a drop of saliva.
You can tell these borrowed dwellings by the unequal size of the
storeys. When the worker has herself bored the channel, she
economizes her space: she knows how costly it is. The cells, in that
case, are all alike, the proper size for the tenant, neither too
large nor too small. In this box, which has cost weeks of labour, the
insect has to house the largest possible number of larvae, while
allotting the necessary amount of room to each. Method in the
superposition of the floors and economy of space are here the
absolute rule.
But there is evidence of waste when the insect makes use of a bramble
hollowed by another. This is the case with Tripoxylon figulus. To
obtain the store-rooms wherein to deposit her scanty stock of
Spiders, she divides her borrowed cylinder into very unequal cells,
by means of slender clay partitions. Some are a centimetre (.39
inch.--Translator's Note.) deep, the proper size for the insect;
others are as much as two inches. These spacious rooms, out of all
proportion to the occupier, reveal the reckless extravagance of a
casual proprietress whose title-deeds have cost her nothing.
But, whether they be the original builders or labourers touching up
the work of others, they all alike have their parasites, who
constitute the third class of bramble-dwellers. These have neither
galleries to excavate nor victuals to provide; they lay their egg in
a strange cell; and their grub feeds either on the provisions of the
lawful owner's larva or on that larva itself.
At the head of this population, as regards both the finish and the
magnitude of the structure, stands the Three-pronged Osmia (Osmia
tridentata, DUF. and PER.), to whom this chapter shall be specially
devoted. Her gallery, which has the diameter of a lead pencil,
sometimes descends to a depth of twenty inches. It is at first almost
exactly cylindrical; but, in the course of the victualling, changes
occur which modify it slightly at geometrically determined distances.
The work of boring possesses no great interest. In the month of July,
we see the insect, perched on a bramble-stump, attack the pith and
dig itself a well. When this is deep enough, the Osmia goes down,
tears off a few particles of pith and comes up again to fling her
load outside. This monotonous labour continues until the Bee deems
the gallery long enough, or until, as often happens, she finds
herself stopped by an impassable knot.
Next comes the ration of honey, the laying of the egg and the
partitioning, the last a delicate operation to which the insect
proceeds by degrees from the base to the top. At the bottom of the
gallery, a pile of honey is placed and an egg laid upon the pile;
then a partition is built to separate this cell from the next, for
each larva must have its special chamber, about a centimetre and a
half (.58 inch.--Translator's Note.) long, having no communication
with the chambers adjoining. The materials employed for this
partition are bramble-sawdust, glued into a paste with the insects'
saliva. Whence are these materials obtained? Does the Osmia go
outside, to gather on the ground the rubbish which she flung out when
boring the cylinder? On the contrary, she is frugal of her time and
has better things to do than to pick up the scattered particles from
the soil. The channel, as I said, is at first uniform in size, almost
cylindrical; its sides still retain a thin coating of pith, forming
the reserves which the Osmia, as a provident builder, has economized
wherewith to construct the partitions. So she scrapes away with her
mandibles, keeping within a certain radius, a radius that corresponds
with the dimensions of the cell which she is going to build next;
moreover, she conducts her work in such a way as to hollow out more
in the middle and leave the two ends contracted. In this manner, the
cylindrical channel of the start is succeeded, in the worked portion,
by an ovoid cavity flattened at both ends, a space resembling a
little barrel. This space will form the second cell.
As for the rubbish, it is utilized on the spot for the lid or cover
that serves as a ceiling for one cell and a floor for the next. Our
own master-builders could not contrive more successfully to make the
best use of their labourers' time. On the floor thus obtained, a
second ration of honey is placed; and an egg is laid on the surface
of the paste. Lastly, at the upper end of the little barrel, a
partition is built with the scrapings obtained in the course of the
final work on the third cell, which itself is shaped like a flattened
ovoid. And so the work goes on, cell upon cell, each supplying the
materials for the partition separating it from the one below. On
reaching the end of the cylinder, the Osmia closes up the case with a
thick layer of the same mortar. Then that bramble-stump is done with;
the Bee will not return to it. If her ovaries are not yet exhausted,
other dry stems will be exploited in the same fashion.
The number of cells varies greatly, according to the qualities of the
stalk. If the bramble-stump be long, regular and smooth, we may count
as many as fifteen: that, at least, is the highest figure which my
observations have supplied. To obtain a good idea of the internal
distribution, we must split the stalk lengthwise, in the winter, when
the provisions have long been consumed and when the larvae are
wrapped in their cocoons. We then see that, at regular intervals, the
case becomes slightly narrower; and in each of the necks thus formed
a circular disk is fixed, a partition one or two millimetres thick.
(.039 to .079 inch.--Translator's Note.) The rooms separated by these
partitions form so many little barrels or kegs, each compactly filled
with a reddish, transparent cocoon, through which the larva shows,
bent into a fish-hook. The whole suggests a string of rough, oval
amber beads, touching at their amputated ends.
In this string of cocoons, which is the oldest, which the youngest?
The oldest is obviously the bottom one, the one whose cell was the
first built; the youngest is the one at the top of the row, the one
in the cell last built. The oldest of the larvae starts the pile,
down at the bottom of the gallery; the latest arrival ends it at the
top; and those in between follow upon one another, according to age,
from base to apex.
Let us next observe that there is no room in the shaft for two Osmiae
at a time on the same level, for each cocoon fills up the storey, the
keg that belongs to it, without leaving any vacant space; let us also
remark that, when they attain the stage of perfection, the Osmiae
must all emerge from the shaft by the only orifice which the bramble-
stem boasts, the orifice at the top. There is here but one obstacle,
easy to overcome: a plug of glued pith, of which the insect's
mandibles make short work. Down below, the stalk offers no ready
outlet; besides, it is prolonged underground indefinitely by the
roots. Everywhere else is the ligneous fence, generally too hard and
thick to break through. It is inevitable therefore that all the
Osmiae, when the time comes to quit their dwelling, should go out by
the top; and, as the narrowness of the shaft bars the passage of the
preceding insect as long as the next insect, the one above it,
remains in position, the removal must begin at the top, extend from
cell to cell and end at the bottom. Consequently, the order of exit
is the converse to the order of birth: the younger Osmiae leave the
nest first, their elders leave it last.
The oldest, that is to say, the bottom one, was the first to finish
her supply of honey and to spin her cocoon. Taking precedence of all
her sisters in the whole series of her actions, she was the first to
burst her silken bag and to destroy the ceiling that closes her room:
at least, that is what the logic of the situation takes for granted.
In her anxiety to get out, how will she set about her release? The
way is blocked by the nearest cocoons, as yet intact. To clear
herself a passage through the string of those cocoons would mean to
exterminate the remainder of the brood; the deliverance of one would
mean the destruction of all the rest. Insects are notoriously
obstinate in their actions and unscrupulous in their methods. If the
Bee at the bottom of the shaft wants to leave her lodging, will she
spare those who bar her road?
The difficulty is great, obviously; it seems insuperable. Thereupon
we become suspicious: we begin to wonder if the emergence from the
cocoon, that is to say, the hatching, really takes place in the order
of primogeniture. Might it not be--by a very singular exception, it
is true, but one which is necessary in such circumstances--that the
youngest of the Osmiae bursts her cocoon first and the oldest last;
in short, that the hatching proceeds from one chamber to the next in
the inverse direction to that which the age of the occupants would
lead us to presume? In that case, the whole difficulty would be
removed: each Osmia, as she rent her silken prison, would find a
clear road in front of her, the Osmiae nearer the outlet having gone
out before her. But is this really how things happen? Our theories
very often do not agree with the insect's practice; even where our
reasoning seems most logical, we should be more prudent to see what
happens before venturing on any positive statements. Leon Dufour was
not so prudent when he, the first in the field, took this little
problem in hand. He describes to us the habits of an Odynerus
(Odynerus rubicola, DUF.) who piles up clay cells in the shaft of a
dry bramble-stalk; and, full of enthusiasm for his industrious Wasp,
he goes on to say:
'Picture a string of eight cement shells, placed end to end and
closely wedged inside a wooden sheath. The lowest was undeniably made
first and consequently contains the first-laid egg, which, according
to rules, should give birth to the first winged insect. How do you
imagine that the larva in that first shell was bidden to waive its
right of primogeniture and only to complete its metamorphosis after
all its juniors? What are the conditions brought into play to produce
a result apparently so contrary to the laws of nature? Humble
yourself in the presence of the reality and confess your ignorance,
rather than attempt to hide your embarrassment under vain
explanations!
'If the first egg laid by the busy mother were destined to be the
first-born of the Odyneri, that one, in order to see the light
immediately after achieving wings, would have had the option either
of breaking through the double walls of his prison or of perforating,
from bottom to top, the seven shells ahead of him, in order to emerge
through the truncate end of the bramble-stem. Now nature, while
refusing any way of escape laterally, was also bound to veto any
direct invasion, the brutal gimlet-work which would inevitably have
sacrificed seven members of one family for the safety of an only son.
Nature is as ingenious in design as she is fertile in resource, and
she must have foreseen and forestalled every difficulty. She decided
that the last-built cradle should yield the first-born child; that
this one should clear the road for his next oldest brother, the
second for the third and so on. And this is the order in which the
birth of our Odyneri of the Brambles actually takes place.'
Yes, my revered master, I will admit without hesitation that the
bramble-dwellers leave their sheath in the converse order to that of
their ages: the youngest first, the oldest last; if not invariably,
at least very often. But does the hatching, by which I mean the
emergence from the cocoon, take place in the same order? Does the
evolution of the elder wait upon that of the younger, so that each
may give those who would bar his passage time to effect their
deliverance and to leave the road clear? I very much fear that logic
has carried your deductions beyond the bounds of reality. Rationally
speaking, my dear sir, nothing could be more accurate than your
inferences; and yet we must forgo the theory of the strange inversion
which you suggest. None of the Bramble-bees with whom I have
experimented behaves after that fashion. I know nothing personal
about Odynerus rubicola, who appears to be a stranger in my district;
but, as the method of leaving must be almost the same when the
habitation is exactly similar, it is enough, I think, to experiment
with some of the bramble-dwellers in order to learn the history of
the rest.
My studies will, by preference, bear upon the Three-pronged Osmia,
who lends herself more readily to laboratory experiments, both
because she is stronger and because the same stalk will contain a
goodly number of her cells. The first fact to be ascertained is the
order of hatching. I take a glass tube, closed at one end, open at
the other and of a diameter similar to that of the Osmia's tunnel. In
this I place, one above the other, exactly in their natural order,
the ten cocoons, or thereabouts, which I extract from a stump of
bramble. The operation is performed in winter. The larvae, at that
time, have long been enveloped in their silken case. To separate the
cocoons from one another, I employ artificial partitions consisting
of little round disks of sorghum, or Indian millet, about half a
centimetre thick. (About one-fifth of an inch.--Translator's Note.)
This is a white pith, divested of its fibrous wrapper and easy for
the Osmia's mandibles to attack. My diaphragms are much thicker than
the natural partitions; this is an advantage, as we shall see. In any
case, I could not well use thinner ones, for these disks must be able
to withstand the pressure of the rammer which places them in position
in the tube. On the other hand, the experiment showed me that the
Osmia makes short work of the material when it is a case of drilling
a hole through it.
To keep out the light, which would disturb my insects destined to
spend their larval life in complete darkness, I cover the tube with a
thick paper sheath, easy to remove and replace when the time comes
for observation. Lastly, the tubes thus prepared and containing
either Osmiae or other bramble-dwellers are hung vertically, with the
opening at the top, in a snug corner of my study. Each of these
appliances fulfils the natural conditions pretty satisfactorily: the
cocoons from the same bramble-stick are stacked in the same order
which they occupied in the native shaft, the oldest at the bottom of
the tube and the youngest close to the orifice; they are isolated by
means of partitions; they are placed vertically, head upwards;
moreover, my device has the advantage of substituting for the opaque
wall of the bramble a transparent wall which will enable me to follow
the hatching day by day, at any moment which I think opportune.
The male Osmia splits his cocoon at the end of June and the female at
the beginning of July. When this time comes, we must redouble our
watch and inspect the tubes several times a day if we would obtain
exact statistics of the births. Well, during the six years that I
have studied this question, I have seen and seen again, ad nauseam;
and I am in a position to declare that there is no order governing
the sequence of hatchings, absolutely none. The first cocoon to burst
may be the one at the bottom of the tube, the one at the top, the one
in the middle or in any other part, indifferently. The second to be
split may adjoin the first or it may be removed from it by a number
of spaces, either above or below. Sometimes several hatchings occur
on the same day, within the same hour, some farther back in the row
of cells, some farther forward; and this without any apparent reason
for the simultaneity. In short, the hatchings follow upon one
another, I will not say haphazard--for each of them has its appointed
place in time, determined by impenetrable causes--but at any rate
contrary to our calculations, based on this or the other
consideration.
Had we not been deceived by our too shallow logic, we might have
foreseen this result. The eggs are laid in their respective cells at
intervals of a few days, of a few hours. How can this slight
difference in age affect the total evolution, which lasts a year?
Mathematical accuracy has nothing to do with the case. Each germ,
each grub has its individual energy, determined we know not how and
varying in each germ or grub. This excess of vitality belongs to the
egg before it leaves the ovary. Might it not, at the moment of
hatching, be the cause why this or that larva takes precedence of its
elders or its juniors, chronology being altogether a secondary
consideration? When the hen sits upon her eggs, is the oldest always
the first to hatch? In the same way, the oldest larva, lodged in the
bottom storey, need not necessarily reach the perfect state first.
A second argument, had we reflected more deeply on the matter, would
have shaken our faith in any strict mathematical sequence. The same
brood forming the string of cocoons in a bramble-stem contains both
males and females; and the two sexes are divided in the series
indiscriminately. Now it is the rule among the Bees for the males to
issue from the cocoon a little earlier than the females. In the case
of the Three-pronged Osmia, the male has about a week's start.
Consequently, in a populous gallery, there is always a certain number
of males, who are hatched seven or eight days before the females and
who are distributed here and there over the series. This would be
enough to make any regular hatching-sequence impossible in either
direction.
These surmises accord with the facts: the chronological sequence of
the cells tells us nothing about the chronological sequence of the
hatchings, which take place without any definite order. There is,
therefore, no surrender of rights of primogeniture, as Leon Dufour
thought: each insect, regardless of the others, bursts its cocoon
when its time comes; and this time is determined by causes which
escape our notice and which, no doubt, depend upon the potentialities
of the egg itself. It is the case with the other bramble-dwellers
which I have subjected to the same test (Osmia detrita, Anthidium
scapulare, Solenius vagus, etc.); and it must also be the case with
Odynerus rubicola: so the most striking analogies inform us.
Therefore the singular exception which made such an impression on
Dufour's mind is a sheer logical illusion.
An error removed is tantamount to a truth gained; and yet, if it were
to end here, the result of my experiment would possess but slight
value. After destruction, let us turn to construction; and perhaps we
shall find the wherewithal to compensate us for an illusion lost. Let
us begin by watching the exit.
The first Osmia to leave her cocoon, no matter what place she
occupies in the series, forthwith attacks the ceiling separating her
from the floor above. She cuts a fairly clean hole in it, shaped like
a truncate cone, having its larger base on the side where the Bee is
and its smaller base opposite. This conformation of the exit-door is
a characteristic of the work. When the insect tries to attack the
diaphragm, it first digs more or less at random; then, as the boring
progresses, the action is concentrated upon an area which narrows
until it presents no more than just the necessary passage. Nor is the
cone-shaped aperture special to the Osmia: I have seen it made by the
other bramble-dwellers through my thick disks of sorghum-pith. Under
natural conditions, the partitions, which, for that matter, are very
thin, are destroyed absolutely, for the contraction of the cell at
the top leaves barely the width which the insect needs. The truncate,
cone-shaped breach has often been of great use to me. Its wide base
made it possible for me, without being present at the work, to judge
which of the two neighbouring Osmiae had pierced the partition; it
told me the direction of a nocturnal migration which I had been
unable to witness.
The first-hatched Osmia, wherever she may be, has made a hole in her
ceiling. She is now in the presence of the next cocoon, with her head
at the opening of the hole. In front of her sister's cradle, she
usually stops, consumed with shyness; she draws back into her cell,
flounders among the shreds of the cocoon and the wreckage of the
ruined ceiling; she waits a day, two days, three days, more if
necessary. Should impatience gain the upper hand, she tries to slip
between the wall of the tunnel and the cocoon that blocks the way.
She even undertakes the laborious work of gnawing at the wall, so as
to widen the interval, if possible. We find these attempts, in the
shaft of a bramble, at places where the pith is removed down to the
very wood, where the wood itself is gnawed to some depth. I need
hardly say that, although these lateral inroads are perceptible after
the event, they escape the eye at the moment when they are being
made.
If we would witness them, we must slightly modify the glass
apparatus. I line the inside of the tube with a thick piece of whity-
brown packing-paper, but only over one half of the circumference; the
other half is left bare, so that I may watch the Osmia's attempts.
Well, the captive insect fiercely attacks this lining, which to its
eyes represents the pithy layer of its usual abode; it tears it away
by tiny particles and strives to cut itself a road between the cocoon
and the glass wall. The males, who are a little smaller, have a
better chance of success than the females. Flattening themselves,
making themselves thin, slightly spoiling the shape of the cocoon,
which, however, thanks to its elasticity, soon recovers its first
condition, they slip through the narrow passage and reach the next
cell. The females, when in a hurry to get out, do as much, if they
find the tube at all amenable to the process. But no sooner is the
first partition passed than a second presents itself. This is pierced
in its turn. In the same way will the third be pierced and others
after that, if the insect can manage them, as long as its strength
holds out. Too weak for these repeated borings, the males do not go
far through my thick plugs. If they contrive to cut through the
first, it is as much as they can do; and, even so, they are far from
always succeeding. But, in the conditions presented by the native
stalk, they have only feeble tissues to overcome; and then, slipping,
as I have said, between the cocoon and the wall, which is slightly
worn owing to the circumstances described, they are able to pass
through the remaining occupied chambers and to reach the outside
first, whatever their original place in the stack of cells. It is
just possible that their early eclosion forces this method of exit
upon them, a method which, though often attempted, does not always
succeed. The females, furnished with stronger tools, make greater
progress in my tubes. I see some who pierce three or four partitions,
one after the other, and are so many stages ahead before those whom
they have left behind are even hatched. While they are engaged in
this long and toilsome operation, others, nearer to the orifice, have
cleared a passage whereof those from a distance will avail
themselves. In this way, it may happen that, when the width of the
tube permits, an Osmia in a back row will nevertheless be one of the
first to emerge.
In the bramble-stem, which is of exactly the same diameter as the
cocoon, this escape by the side of the column appears hardly
practicable, except to a few males; and even these have to find a
wall which has so much pith that by removing it they can effect a
passage. Let us then imagine a tube so narrow as to prevent any exit
save in the natural sequence of the cells. What will happen? A very
simple thing. The newly-hatched Osmia, after perforating his
partition, finds himself faced with an unbroken cocoon that obstructs
the road. He makes a few attempts upon the sides and, realizing his
impotence, retires into his cell, where he waits for days and days,
until his neighbour bursts her cocoon in her turn. His patience is
inexhaustible. However, it is not put to an over long test, for
within a week, more or less, the whole string of females is hatched.
When two neighbouring Osmiae are released at the same time, mutual
visits are paid through the aperture between the two rooms: the one
above goes down to the floor below; the one below goes up to the
floor above; sometimes both of them are in the same cell together.
Might not this intercourse tend to cheer them and encourage them to
patience? Meanwhile, slowly, doors are opening here and there through
the separating walls; the road is cleared by sections; and a moment
arrives when the leader of the file walks out. The others follow, if
ready; but there are always laggards who keep the rear-ranks waiting
until they are gone.
To sum up, first, the hatching of the larvae takes place without any
order; secondly, the exodus proceeds regularly from summit to base,
but only in consequence of the insect's inability to move forward so
long as the upper cells are not vacated. We have here not an
exceptional evolution, in the inverse ratio to age, but the simple
impossibility of emerging otherwise. Should a chance occur of going
out before its turn, the insect does not fail to seize it, as we can
see by the lateral movements which send the impatient ones a few
ranks ahead and even release the more favoured altogether. The only
remarkable thing that I perceive is the scrupulous respect shown to
the as yet unopened neighbouring cocoon. However eager to come out,
the Osmia is most careful not to touch it with his mandibles: it is
taboo. He will demolish the partition, he will gnaw the side-wall
fiercely, even though there be nothing left but wood, he will reduce
everything around him to dust; but touch a cocoon that obstructs his
way? Never! He will not make himself an outlet by breaking up his
sisters' cradles.
It may happen that the Osmia's patience is in vain and that the
barricade that blocks the way never disappears at all. Sometimes, the
egg in a cell does not mature; and the unconsumed provisions dry up
and become a compact, sticky, mildewed plug, through which the
occupants of the floors below could never clear themselves a passage.
Sometimes, again, a grub dies in its cocoon; and the cradle of the
deceased, now turned into a coffin, forms an everlasting obstacle.
How shall the insect cope with such grave circumstances?
Among the many bramble-stumps which I have collected, some few have
presented a remarkable peculiarity. In addition to the orifice at the
top, they had at the side one and sometimes two round apertures that
looked as though they had been punched out with an instrument. On
opening these stalks, which were old, deserted nests, I discovered
the cause of these very exceptional windows. Above each of them was a
cell full of mouldy honey. The egg had perished and the provisions
remained untouched: hence the impossibility of getting out by the
ordinary road. Walled in by the unsurmountable obstacle, the Osmia on
the floor below had contrived an outlet through the side of the
shaft; and those in the lower storeys had benefited by this ingenious
innovation. The usual door being inaccessible, a side-window had been
opened by means of the insect's jaws. The cocoons, torn, but still in
position in the lower rooms, left no doubt as to this eccentric mode
of exit. The same fact, moreover, was repeated, in several bramble-
stumps, in the case of Osmia tridentata; it was likewise repeated in
the case of Anthidium scapulare. The observation was worth confirming
by experiment.
I select a bramble-stem with the thinnest rind possible, so as to
facilitate the Osmiae's work. I split it in half, thus obtaining a
smooth-sided trough which will enable me to judge better of future
exits. The cocoons are next laid out in one of the troughs. I
separate them with disks of sorghum, covering both surfaces of the
disk with a generous layer of sealing-wax, a material which the
Osmia's mandibles are not able to attack. The two troughs are then
placed together and fastened. A little putty does away with the joint
and prevents the least ray of light from penetrating. Lastly, the
apparatus is hung up perpendicularly, with the cocoons' heads up. We
have now only to wait. None of the Osmiae can get out in the usual
manner, because each of them is confined between two partitions
coated with sealing-wax. There is but one resource left to them if
they would emerge into the light of day, that is, for each of them to
open a side-window, provided always that they possess the instinct
and the power to do so.
In July, the result is as follows: of twenty Osmiae thus immured, six
succeed in boring a round hole through the wall and making their way
out; the others perish in their cells, without managing to release
themselves. But, when I open the cylinder, when I separate the two
wooden troughs, I realize that all have attempted to escape through
the side, for the wall of each cell bears traces of gnawing
concentrated upon one spot. All, therefore, have acted in the same
way as their more fortunate sisters; they did not succeed, because
their strength failed them. Lastly, in my glass tubes, part-lined
with a thick piece of packing-paper, I often see attempts at making a
window in the side of the cell: the paper is pierced right through
with a round hole.
This then is yet another result which I am glad to record in the
history of the bramble-dwellers. When the Osmia, the Anthidium and
probably others are unable to emerge through the customary outlet,
they take an heroic decision and perforate the side of the shaft. It
is the last resource, resolved upon after other methods have been
tried in vain. The brave, the strong succeed; the weak perish in the
attempt.
Supposing that all the Osmiae possessed the necessary strength of jaw
as well as the instinct for this sideward boring, it is clear that
egress from each cell through a special window would be much more
advantageous than egress through the common door. The Bee could
attend to his release as soon as he was hatched, instead of
postponing it until after the emancipation of those who come before
him; he would thus escape long waits, which too often prove fatal. In
point of fact, it is no uncommon thing to find bramble-stalks in
which several Osmiae have died in their cells, because the upper
storeys were not vacated in time. Yes, there would be a precious
advantage in that lateral opening, which would not leave each
occupant at the mercy of his environment: many die that would not
die. All the Osmiae, when compelled by circumstances, resort to this
supreme method; all have the instinct for lateral boring; but very
few are able to carry the work through. Only the favourites of fate
succeed, those more generously endowed with strength and
perseverance.
If the famous law of natural selection, which is said to govern and
transform the world, had any sure foundation; if really the fittest
removed the less fit from the scene; if the future were to the
strongest, to the most industrious, surely the race of Osmiae, which
has been perforating bramble-stumps for ages, should by this time
have allowed its weaker members, who go on obstinately using the
common outlet, to die out and should have replaced them, down to the
very last one, by the stalwart drillers of side-openings. There is an
opportunity here for immense progress; the insect is on the verge of
it and is unable to cross the narrow intervening line. Selection has
had ample time to make its choice; and yet, though there be a few
successes, the failures exceed them in very large measure. The race
of the strong has not abolished the race of the weak: it remains
inferior in numbers, as doubtless it has been since all time. The law
of natural selection impresses me with the vastness of its scope;
but, whenever I try to apply it to actual facts, it leaves me
whirling in space, with nothing to help me to interpret realities. It
is magnificent in theory, but it is a mere gas-bubble in the face of
existing conditions. It is majestic, but sterile. Then where is the
answer to the riddle of the world? Who knows? Who will ever know?
Let us waste no more time in this darkness, which idle theorizing
will not dispel; let us return to facts, humble facts, the only
ground that does not give way under our feet. The Osmia respects her
neighbour's cocoon; and her scruples are so great that, after vainly
trying to slip between that cocoon and the wall, or else to open a
lateral outlet, she lets herself die in her cell rather than effect
an egress by forcing her way through the occupied cells. When the
cocoon that blocks the way contains a dead instead of a live grub,
will the result be the same?
In my glass tubes, I let Osmia-cocoons containing a live grub
alternate with Osmia-cocoons in which the grub has been asphyxiated
by the fumes of sulphocarbonic acid. As usual, the storeys are
separated by disks of sorghum. The anchorites, when hatched, do not
hesitate long. Once the partition is pierced, they attack the dead
cocoons, go right through them, reducing the dead grub, now dry and
shrivelled, to dust, and at last emerge, after wrecking everything in
their path. The dead cocoons, therefore, are not spared; they are
treated as would be any other obstacle capable of attack by the
mandibles. The Osmia looks upon them as a mere barricade to be
ruthlessly overturned. How is she apprised that the cocoon, which has
undergone no outward change, contains a dead and not a live grub? It
is certainly not by sight. Can it be by sense of smell? I am always a
little suspicious of that sense of smell of which we do not know the
seat and which we introduce on the slightest provocation as a
convenient explanation of that which may transcend our explanatory
powers.
My next test is made with a string of live cocoons. Of course, I
cannot take all these from the same species, for then the experiment
would not differ from the one which we have already witnessed; I take
them from two different species which leave their bramble-stem at
separate periods. Moreover, these cocoons must have nearly the same
diameter to allow of their being stacked in a tube without leaving an
empty space between them and the wall. The two species adopted are
Solenius vagus, which quits the bramble at the end of June, and Osmia
detrita, which comes a little earlier, in the first fortnight of the
same month. I therefore alternate Osmia-cocoons and Solenius-cocoons,
with the latter at the top of the series, either in glass tubes or
between two bramble-troughs joined into a cylinder.
The result of this promiscuity is striking. The Osmiae, which mature
earlier, emerge; and the Solenius-cocoons, as well as their
inhabitants, which by this time have reached the perfect stage, are
reduced to shreds, to dust, wherein it is impossible for me to
recognize a vestige, save perhaps here and there a head, of the
exterminated unfortunates. The Osmia, therefore, has not respected
the live cocoons of a foreign species: she has passed out over the
bodies of the intervening Solenii. Did I say passed over their
bodies? She has passed through them, crunched the laggards between
her jaws, treated them as cavalierly as she treats my disks. And yet
those barricades were alive. No matter: when her hour came, the Osmia
went ahead, destroying everything upon her road. Here, at any rate,
is a law on which we can rely: the supreme indifference of the animal
to all that does not form part of itself and its race.
And what of the sense of smell, distinguishing the dead from the
living? Here, all are alive; and the Bee pierces her way as through a
row of corpses. If I am told that the smell of the Solenii may differ
from that of the Osmiae, I shall reply that such extreme subtlety in
the insect's olfactory apparatus seems to me a rather far-fetched
supposition. Then what is my explanation of the two facts? The
explanation? I have none to give! I am quite content to know that I
do not know, which at least spares me many vain lucubrations. And so
I do not know how the Osmia, in the dense darkness of her tunnel,
distinguishes between a live cocoon and a dead cocoon of the same
species; and I know just as little how she succeeds in recognizing a
strange cocoon. Ah, how clearly this confession of ignorance proves
that I am behind the times! I am deliberately missing a glorious
opportunity of stringing big words together and arriving at nothing.
The bramble-stump is perpendicular, or nearly so; its opening is at
the top. This is the rule under natural conditions. My artifices are
able to alter that state of things; I can place the tube vertically
or horizontally; I can turn its one orifice either up or down;
lastly, I can leave the channel open at both ends, which will give
two outlets. What will happen under these several conditions? That is
what we shall examine with the Three-pronged Osmia.
The tube is hung perpendicularly, but closed at the top and open at
the bottom; in fact, it represents a bramble-stump turned upside
down. To vary and complicate the experiment, the strings of cocoons
are arranged differently in different tubes. In some of them, the
heads of the cocoons are turned downwards, towards the opening; in
others, they are turned upwards, towards the closed end; in others
again, the cocoons alternate in direction, that is to say, they are
placed head to head and rear to rear, turn and turn about. I need not
say that the separating floors are of sorghum.
The result is identical in all these tubes. If the Osmiae have their
heads pointing upwards, they attack the partition above them, as
happens under normal conditions; if their heads point downwards, they
turn round in their cells and set to work as usual. In short, the
general outward trend is towards the top, in whatever position the
cocoon be placed.
We here see manifestly at work the influence of gravity, which warns
the insect of its reversed position and makes it turn round, even as
it would warn us if we ourselves happened to be hanging head
downwards. In natural conditions, the insect has but to follow the
counsels of gravity, which tells it to dig upwards, and it will
infallibly reach the exit-door situated at the upper end. But, in my
apparatus, these same counsels betray it: it goes towards the top,
where there is no outlet. Thus misled by my artifices, the Osmiae
perish, heaped up on the higher floors and buried in the ruins.
It nevertheless happens that attempts are made to clear a road
downwards. But it is rare for the work to lead to anything in this
direction, especially in the case of the middle or upper cells. The
insect is little inclined for this progress, the opposite to that to
which it is accustomed; besides, a serious difficulty arises in the
course of this reversed boring. As the Bee flings the excavated
materials behind her, these fall back of their own weight under her
mandibles; the clearance has to be begun anew. Exhausted by her
Sisyphean task, distrustful of this new and unfamiliar method, the
Osmia resigns herself and expires in her cell. I am bound to add,
however, that the Osmiae in the lower storeys, those nearest the
exit--sometimes one, sometimes two or three--do succeed in escaping.
In that case, they unhesitatingly attack the partitions below them,
while their companions, who form the great majority, persist and
perish in the upper cells.
It was easy to repeat the experiment without changing anything in the
natural conditions, except the direction of the cocoons: all that I
had to do was to hang up some bramble-stumps as I found them,
vertically, but with the opening downwards. Out of two stalks thus
arranged and peopled with Osmiae, not one of the insects succeeded in
emerging. All the Bees died in the shaft, some turned upwards, others
downwards. On the other hand, three stems occupied by Anthidia
discharged their population safe and sound. The outgoing was effected
at the bottom, from first to last, without the least impediment. Must
we take it that the two sorts of Bees are not equally sensitive to
the influences of gravity? Can the Anthidium, built to pass through
the difficult obstacle of her cotton wallets, be better-adapted than
the Osmia to make her way through the wreckage that keeps falling
under the worker's feet; or, rather, may not this very cotton-waste
put a stop to these cataracts of rubbish which must naturally drive
the insect back? This is all quite possible; but I can say nothing
for certain.
Let us now experiment with vertical tubes open at both ends. The
arrangements, save for the upper orifice, are the same as before. The
cocoons, in some of the tubes, have their heads turned down; others,
up; in others again, their positions alternate. The result is similar
to what we have seen above. A few Osmiae, those nearest the bottom
orifice, take the lower road, whatever the direction first occupied
by the cocoon; the others, composing by far the larger number, take
the higher road, even when the cocoon is placed upside down. As both
doors are free, the outgoing is effected at either end with success.
What are we to conclude from all these experiments? First, that
gravity guides the insect towards the top, where the natural door is,
and makes it turn in its cell when the cocoon has been reversed.
Secondly, I seem to suspect an atmospheric influence and, in any
case, some second cause that sends the insect to the outlet. Let us
admit that this cause is the proximity of the outer air acting upon
the anchorite through the partitions.
The animal then is subject, on the one hand, to the promptings of
gravity, and this to an equal degree for all, whatever the storey
inhabited. Gravity is the common guide of the whole series from base
to top. But those in the lower boxes have a second guide, when the
bottom end is open. This is the stimulus of the adjacent air, a more
powerful stimulus than that of gravity. The access of the air from
without is very slight, because of the partitions; while it can be
felt in the nethermost cells, it must decrease rapidly as the storeys
ascend. Wherefore the bottom insects, very few in number, obeying the
preponderant influence, that of the atmosphere, make for the lower
outlet and reverse, if necessary, their original position; those
above, on the contrary, who form the great majority, being guided
only by gravity when the upper end is closed, make for that upper
end. It goes without saying that, if the upper end be open at the
same time as the other, the occupants of the top storeys will have a
double incentive to take the ascending path, though this will not
prevent the dwellers on the lower floors from obeying, by preference,
the call of the adjacent air and adopting the downward road.
I have one means left whereby to judge of the value of my
explanation, namely, to experiment with tubes open at both ends and
lying horizontally. The horizontal position has a twofold advantage.
In the first place, it removes the insect from the influence of
gravity, inasmuch as it leaves it indifferent to the direction to be
taken, the right or the left. In the second place, it does away with
the descent of the rubbish which, falling under the worker's feet
when the boring is done from below, sooner or later discourages her
and makes her abandon her enterprise.
There are a few precautions to be observed for the successful conduct
of the experiment; I recommend them to any one who might care to make
the attempt. It is even advisable to remember them in the case of the
tests which I have already described. The males, those puny
creatures, not built for work, are sorry labourers when confronted
with my stout disks. Most of them perish miserably in their glass
cells, without succeeding in piercing their partitions right through.
Moreover, instinct has been less generous to them than to the
females. Their corpses, interspersed here and there in the series of
the cells, are disturbing causes, which it is wise to eliminate. I
therefore choose the larger, more powerful-looking cocoons. These,
except for an occasional unavoidable error, belong to females. I pack
them in tubes, sometimes varying their position in every way,
sometimes giving them all a like arrangement. It does not matter
whether the whole series comes from one and the same bramble-stump or
from several: we are free to choose where we please; the result will
not be altered.
The first time that I prepared one of these horizontal tubes open at
both ends, I was greatly struck by what happened. The series
consisted of ten cocoons. It was divided into two equal batches. The
five on the left went out on the left, the five on the right went out
on the right, reversing, when necessary, their original direction in
the cell. It was very remarkable from the point of view of symmetry;
moreover, it was a very unlikely arrangement among the total number
of possible arrangements, as mathematics will show us.
Let us take n to represent the number of Osmiae. Each of them, once
gravity ceases to interfere and leaves the insect indifferent to
either end of the tube, is capable of two positions, according as she
chooses the exit on the right or on the left. With each of the two
positions of this first Osmia can be combined each of the two
positions of the second, giving us, in all, 2 x 2 = (2 squared)
arrangements. Each of these (2 squared) arrangements can be combined,
in its turn, with each of the two positions of the third Osmia. We
thus obtain 2 x 2 x 2 = (2 cubed) arrangements with three Osmiae; and
so on, each additional insect multiplying the previous result by the
factor 2. With n Osmiae, therefore, the total number of arrangements
is (2 to the power n.)
But note that these arrangements are symmetrical, two by two: a given
arrangement towards the right corresponds with a similar arrangement
towards the left; and this symmetry implies equality, for, in the
problem in hand, it is a matter of indifference whether a fixed
arrangement correspond with the right or left of the tube. The
previous number, therefore, must be divided by 2. Thus, n Osmiae,
according as each of them turns her head to the right or left in my
horizontal tube, are able to adopt (2 to the power n - 1)
arrangements. If n = 10, as in my first experiment, the number of
arrangements becomes (2 to the power 9) = 512.
Consequently, out of 512 ways which my ten insects can adopt for
their outgoing position, there resulted one of those in which the
symmetry was most striking. And observe that this was not an effect
obtained by repeated attempts, by haphazard experiments. Each Osmia
in the left half had bored to the left, without touching the
partition on the right; each Osmia in the right half had bored to the
right, without touching the partition on the left. The shape of the
orifices and the surface condition of the partition showed this, if
proof were necessary. There had been a spontaneous decision, one half
in favour of the left, one half in favour of the right.
The arrangement presents another merit, one superior to that of
symmetry: it has the merit of corresponding with the minimum
expenditure of force. To admit of the exit of the whole series, if
the string consists of n cells, there are originally n partitions to
be perforated. There might even be one more, owing to a complication
which I disregard. There are, I say, at least n partitions to be
perforated. Whether each Osmia pierces her own, or whether the same
Osmia pierces several, thus relieving her neighbours, does not matter
to us: the sum-total of the force expended by the string of Bees will
be in proportion to the number of those partitions, in whatever
manner the exit be effected.
But there is another task which we must take seriously into
consideration, because it is often more troublesome than the boring
of the partition: I mean the work of clearing a road through the
wreckage. Let us suppose the partitions pierced and the several
chambers blocked by the resulting rubbish and by that rubbish only,
since the horizontal position precludes any mixing of the contents of
different chambers. To open a passage for itself through these
rubbish-heaps, each insect will have the smallest effort to make if
it passes through the smallest possible number of cells, in short, if
it makes for the opening nearest to it. These smallest individual
efforts amount, in the aggregate, to the smallest total effort.
Therefore, by proceeding as they did in my experiment, the Osmiae
effect their exit with the least expenditure of energy. It is curious
to see an insect apply the 'principle of least action,' so often
postulated in mechanics.
An arrangement which satisfies this principle, which conforms to the
law of symmetry and which possesses but one chance in 512, is
certainly no fortuitous result. It is determined by a cause; and, as
this cause acts invariably, the same arrangement must be reproduced
if I renew the experiment. I renewed it, therefore, in the years that
followed, with as many appliances as I could find bramble-stumps;
and, at each new test, I saw once more what I had seen with such
interest on the first occasion. If the number be even--and my column
at that time consisted usually of ten--one half goes out on the
right, the other on the left. If the number be odd--eleven, for
instance--the Osmia in the middle goes out indiscriminately by the
right or left exit. As the number of cells to be traversed is the
same on both sides, her expenditure of energy does not vary with the
direction of the exit; and the principle of least action is still
observed.
It was important to discover if the Three-pronged Osmia shared her
capacity, in the first place, with the other bramble-dwellers and, in
the second, with Bees differently housed, but also destined
laboriously to cut a new road for themselves when the hour comes to
quit the nest. Well, apart from a few irregularities, due either to
cocoons whose larva perished in my tubes before developing, or to
those inexperienced workers, the males, the result was the same in
the case of Anthidium scapulare. The insects divided themselves into
two equal batches, one going to the right, the other to the left.
Tripoxylon figulus left me undecided. This feeble insect is not
capable of perforating my partitions; it nibbles at them a little;
and I had to judge the direction from the marks of its mandibles.
These marks, which are not always very plain, do not yet allow me to
pronounce an opinion. Solenius vagus, who is a skilful borer, behaved
differently from the Osmia. In a column of ten, the whole exodus was
made in one direction.
On the other hand, I tested the Mason-bee of the Sheds, who, when
emerging under natural conditions, has only to pierce her cement
ceiling and is not confronted with a series of cells. Though a
stranger to the environment which I created for her, she gave me a
most positive answer. Of a column of ten laid in a horizontal tube
open at both ends, five made their way to the right and five to the
left. Dioxys cincta, a parasite in the buildings of both species of
Mason-bees, the Chalicodoma of the Sheds and the Chalicodoma of the
Walls (Cf. "The Mason-bees" by J. Henri Fabre, translated by
Alexander Teixeira de Mattos: passim.--Translator's Note.), provided
me with no precise result. The Leaf-cutting Bee (Megachile apicalis,
SPIN. (Cf. Chapter 8 of the present volume.--Translator's Note.)),
who builds her leafy cups in the old cells of the Chalicodoma of the
Walls, acts like the Solenius and directs her whole column towards
the same outlet.
Incomplete as it is, this symmetry shows us how unwise it were to
generalize from the conclusions to which the Three-pronged Osmia
leads us. Whereas some Bees, such as the Anthidium and the
Chalicodoma, share the Osmia's talent for using the twofold exit,
others, such as the Solenius and the Leaf-cutter, behave like a flock
of sheep and follow the first that goes out. The entomological world
is not all of a piece; its gifts are very various: what one is
capable of doing another cannot do; and penetrating indeed would be
the eyes that saw the causes of these differences. Be this as it may,
increased research will certainly show us a larger number of species
qualified to use the double outlet. For the moment, we know three;
and that is enough for our purpose.
I will add that, when the horizontal tube has one of its ends closed,
the whole string of Osmiae makes for the open end, turning round to
do so, if need be.
Now that the facts are set forth, let us, if possible, trace the
cause. In a horizontal tube, gravity no longer acts to determine the
direction which the insect will take. Is it to attack the partition
on the right or that on the left? How shall it decide? The more I
look into the matter, the more do my suspicions fall upon the
atmospheric influence which is felt through the two open ends. Of
what does this influence consist? Is it an effect of pressure, of
hygrometry, of electrical conditions, of properties that escape our
coarser physical attunement? He were a bold man who should undertake
to decide. Are not we ourselves, when the weather is about to alter,
subject to subtle impressions, to sensations which we are unable to
explain? And yet this vague sensitiveness to atmospheric changes
would not be of much help to us in circumstances similar to those of
my anchorites. Imagine ourselves in the darkness and the silence of a
prison-cell, preceded and followed by other similar cells. We possess
implements wherewith to pierce the walls; but where are we to strike
to reach the final outlet and to reach it with the least delay?
Atmospheric influence would certainly never guide us.
And yet it guides the insect. Feeble though it be, through the
multiplicity of partitions, it is exercised on one side more than on
the other, because the obstacles are fewer; and the insect, sensible
to the difference between those two uncertainties, unhesitatingly
attacks the partition which is nearer to the open air. Thus is
decided the division of the column into two converse sections, which
accomplish the total liberation with the least aggregate of work. In
short, the Osmia and her rivals 'feel' the free space. This is yet
one more sensory faculty which evolution might well have left us, for
our greater advantage. As it has not done so, are we then really, as
many contend, the highest expression of the progress accomplished,
throughout the ages, by the first atom of glair expanded into a cell?
CHAPTER 2. THE OSMIAE.
February has its sunny days, heralding spring, to which rude winter
will reluctantly yield place. In snug corners, among the rocks, the
great spurge of our district, the characias of the Greeks, the jusclo
of the Provencals, begins to lift its drooping inflorescence and
discreetly opens a few sombre flowers. Here the first Midges of the
year will come to slake their thirst. By the time that the tip of the
stalks reaches the perpendicular, the worst of the cold weather will
be over.
Another eager one, the almond-tree, risking the loss of its fruit,
hastens to echo these preludes to the festival of the sun, preludes
which are too often treacherous. A few days of soft skies and it
becomes a glorious dome of white flowers, each twinkling with a
roseate eye. The country, which still lacks green, seems dotted
everywhere with white-satin pavilions. 'Twould be a callous heart
indeed that could resist the magic of this awakening.
The insect nation is represented at these rites by a few of its more
zealous members. There is first of all the Honey-bee, the sworn enemy
of strikes, who profits by the least lull of winter to find out if
some rosemary is not beginning to open somewhere near the hive. The
droning of the busy swarm fills the flowery vault, while a snow of
petals falls softly to the foot of the tree.
Together with the population of harvesters there mingles another,
less numerous, of mere drinkers, whose nesting-time has not yet
begun. This is the colony of the Osmiae, with their copper-coloured
skin and bright-red fleece. Two species have come hurrying up to take
part in the joys of the almond-tree: first, the Horned Osmia, clad in
black velvet on the head and breast and in red velvet on the abdomen;
and, a little later, the Three-horned Osmia, whose livery must be red
and red only. These are the first delegates despatched by the pollen-
gleaners to ascertain the state of the season and attend the festival
of the early blooms. 'Tis but a moment since they burst their cocoon,
the winter abode: they have left their retreats in the crevices of
the old walls; should the north wind blow and set the almond-tree
shivering, they will hasten to return to them. Hail to you, O my dear
Osmiae, who yearly, from the far end of the harmas (The piece of
waste ground in which the author studied his insects in their natural
state. Cf. "The Life of the Fly" by J. Henri Fabre, translated by
Alexander Teixeira de Mattos: chapter 1.--Translator's Note.),
opposite snow-capped Ventoux (A mountain in the Provencal Alps, near
Carpentras and Serignan, 6,271 feet.--Translator's Note.), bring me
the first tidings of the awakening of the insect world! I am one of
your friends; let us talk about you a little.
Most of the Osmiae of my region have none of the industry of their
kinswomen of the brambles, that is to say, they do not themselves
prepare the dwelling destined for the laying. They want ready-made
lodgings, such as the old cells and old galleries of Anthophorae and
Chalicodomae. If these favourite haunts are lacking, then a hiding-
place in the wall, a round hole in some bit of wood, the tube of a
reed, the spiral of a dead Snail under a heap of stones are adopted,
according to the tastes of the several species. The retreat selected
is divided into chambers by partition-walls, after which the entrance
to the dwelling receives a massive seal. That is the sum-total of the
building done.
For this plasterer's rather than mason's work, the Horned and the
Three-horned Osmia employ soft earth. This material is different from
the Mason-bee's cement, which will withstand wind and weather for
many years on an exposed pebble; it is a sort of dried mud, which
turns to pap on the addition of a drop of water. The Mason-bee
gathers her cementing-dust in the most frequented and driest portions
of the road; she wets it with a saliva which, in drying, gives it the
consistency of stone. The two Osmiae who are the almond-tree's early
visitors are no chemists: they know nothing of the making and mixing
of hydraulic mortar; they limit themselves to gathering natural
soaked earth, mud in short, which they allow to dry without any
special preparation on their part; and so they need deep and well-
sheltered retreats, into which the rain cannot penetrate, or the work
would fall to pieces.
While exploiting, in friendly rivalry with the Three-horned Osmia,
the galleries which the Mason-bee of the Sheds good-naturedly
surrenders to both, Latreille's Osmia uses different materials for
her partitions and her doors. She chews the leaves of some
mucilaginous plant, some mallow perhaps, and then prepares a sort of
green putty with which she builds her partitions and finally closes
the entrance to the dwelling. When she settles in the spacious cells
of the Masked Anthophora (Anthophora personata, ILLIG.), the entrance
to the gallery, which is wide enough to admit one's finger, is closed
with a voluminous plug of this vegetable paste. On the earthy banks,
hardened by the sun, the home is then betrayed by the gaudy colour of
the lid. It is as though the authorities had closed the door and
affixed to it their great seals of green wax.
So far then as their building-materials are concerned, the Osmiae
whom I have been able to observe are divided into two classes: one
building compartments with mud, the other with a green-tinted
vegetable putty. The first section includes the Horned Osmia and the
Three-horned Osmia, both so remarkable for the horny tubercles on
their faces.
The great reed of the south, the Arundo donax, is often used, in the
country, for rough garden-shelters against the mistral or just for
fences. These reeds, the ends of which are chopped off to make them
all the same length, are planted perpendicularly in the earth. I have
often explored them in the hope of finding Osmia-nests. My search has
very seldom succeeded. The failure is easily explained. The
partitions and the closing-plug of the Horned and of the Three-horned
Osmia are made, as we have seen, of a sort of mud which water
instantly reduces to pap. With the upright position of the reeds, the
stopper of the opening would receive the rain and would become
diluted; the ceilings of the storeys would fall in and the family
would perish by drowning. Therefore the Osmia, who knew of these
drawbacks before I did, refuses the reeds when they are placed
perpendicularly.
The same reed is used for a second purpose. We make canisses of it,
that is to say, hurdles, which, in spring, serve for the rearing of
silk-worms and, in autumn, for the drying of figs. At the end of
April and during May, which is the time when the Osmiae work, the
canisses are indoors, in the silk-worm nurseries, where the Bee
cannot take possession of them; in autumn, they are outside, exposing
their layers of figs and peeled peaches to the sun; but by that time
the Osmiae have long disappeared. If, however, during the spring, an
old, disused hurdle is left out of doors, in a horizontal position,
the Three-horned Osmia often takes possession of it and makes use of
the two ends, where the reeds lie truncated and open.
There are other quarters that suit the Three-horned Osmia, who is not
particular, it seems to me, and will make shift with any hiding-
place, so long as it has the requisite conditions of diameter,
solidity, sanitation and kindly darkness. The most original dwellings
that I know her to occupy are disused Snail-shells, especially the
house of the Common Snail (Helix aspersa). Let us go to the slope of
the hills thick with olive-trees and inspect the little supporting-
walls which are built of dry stones and face the south. In the
crevices of this insecure masonry, we shall reap a harvest of old
Snail-shells, plugged with earth right up to the orifice. The family
of the Three-horned Osmia is settled in the spiral of those shells,
which is subdivided into chambers by mud partitions.
Let us inspect the stone-heaps, especially those which come from the
quarry-works. Here we often find the Field-mouse sitting on a grass
mattress, nibbling acorns, almonds, olive-stones and apricot-stones.
The Rodent varies his diet: to oily and farinaceous foods he adds the
Snail. When he is gone, he has left behind him, under the overhanging
stones, mixed up with the remains of other victuals, an assortment of
empty shells, sometimes plentiful enough to remind me of the heap of
Snails which, cooked with spinach and eaten country-fashion on
Christmas Eve, are flung away next day by the housewife. This gives
the Three-horned Osmia a handsome collection of tenements; and she
does not fail to profit by them. Then again, even if the Field-
mouse's conchological museum be lacking, the same broken stones serve
as a refuge for Garden-snails who come to live there and end by dying
there. When we see Three-horned Osmiae enter the crevices of old
walls and of stone-heaps, there is no doubt about their occupation:
they are getting free lodgings out of the old Snail-shells of those
labyrinths.
The Horned Osmia, who is less common, might easily also be less
ingenious, that is to say, less rich in varieties of houses. She
seems to scorn empty shells. The only homes that I know her to
inhabit are the reeds of the hurdles and the deserted cells of the
Masked Anthophora.
All the other Osmiae whose method of nest-building I know work with
green putty, a paste made of some crushed leaf or other; and none of
them, except Latreille's Osmia, is provided with the horned or
tubercled armour of the mud-kneaders. I should like to know what
plants are used in making the putty; probably each species has its
own preferences and its little professional secrets; but hitherto
observation has taught me nothing concerning these details. Whatever
worker prepare it, the putty is very much the same in appearance.
When fresh, it is always a clear dark green. Later, especially in the
parts exposed to the air, it changes, no doubt through fermentation,
to the colour of dead leaves, to brown, to dull-yellow; and the leafy
character of its origin is no longer apparent. But uniformity in the
materials employed must not lead us to believe in uniformity in the
lodging; on the contrary, this lodging varies greatly with the
different species, though there is a marked predilection in favour of
empty shells. Thus Latreille's Osmia, together with the Three-horned
Osmia, uses the spacious structures of the Mason-bee of the Sheds;
she likes the magnificent cells of the Masked Anthophora; and she is
always ready to establish herself in the cylinder of any reed lying
flat on the ground.
I have already spoken of an Osmia (O. cyanoxantha, PEREZ) who elects
to make her home in the old nests of the Mason-bee of the Pebbles.
(Cf. "The Mason-bees": chapter 10.--Translator's Note.) Her closing-
plug is made of a stout concrete, consisting of fair-sized bits of
gravel sunk in the green paste; but for the inner partitions she
employs only unalloyed putty. As the outer door, situated on the
curve of an unprotected dome, is exposed to the inclemencies of the
weather, the mother has to think of fortifying it. Danger, no doubt,
is the originator of that gritty concrete.
The Golden Osmia (O. aurulenta, LATR.) absolutely insists on an empty
Snail-shell as her residence. The Brown or Girdled Snail, the Garden
Snail and especially the Common Snail, who has a more spacious
spiral, all scattered at random in the grass, at the foot of the
walls and of the sun-swept rocks, furnish her with her usual
dwelling-house. Her dried putty is a kind of felt full of short white
hairs. It must come from some hairy-leaved plant, one of the
Boragineae perhaps, rich both in mucilage and the necessary bristles.
The Red Osmia (O. rufo-hirta, LATR.) has a weakness for the Brown
Snail and the Garden Snail, in whose shells I find her taking refuge
in April when the north-wind blows. I am not yet much acquainted with
her work, which should resemble that of the Golden Osmia.
The Green Osmia (O. viridana, MORAWITZ) takes up her quarters, tiny
creature that she is, in the spiral staircase of Bulimulus radiatus.
It is a very elegant, but very small lodging, to say nothing of the
fact that a considerable portion is taken up with the green-putty
plug. There is just room for two.
The Andrenoid Osmia (O. andrenoides, LATR.), who looks so curious,
with her naked red abdomen, appears to build her nest in the shell of
the Common Snail, where I discover her refuged.
The Variegated Osmia (O. versicolor, LATR.) settles in the Garden
Snail's shell, almost right at the bottom of the spiral.
The Blue Osmia (O. cyanea, KIRB.) seems to me to accept many
different quarters. I have extracted her from old nests of the Mason-
bee of the Pebbles, from the galleries dug in a roadside bank by the
Colletes (A short-tongued Burrowing-bee known also as the Melitta.--
Translator's Note.) and lastly from the cavities made by some digger
or other in the decayed trunk of a willow-tree.
Morawitz' Osmia (O. Morawitzi, PEREZ) is not uncommon in the old
nests of the Mason-bee of the Pebbles, but I suspect her of favouring
other lodgings besides.
The Three-pronged Osmia (O. tridentata, DUF. and PER.) creates a home
of her own, digging herself a channel with her mandibles in dry
bramble and sometimes in danewort. It mixes a few scrapings of
perforated pith with the green paste. Its habits are shared by the
Ragged Osmia (O. detrita, PEREZ) and by the Tiny Osmia (O. parvula,
DUF.)
The Chalicodoma works in broad daylight, on a tile, on a pebble, on a
branch in the hedge; none of her trade-practises is kept a secret
from the observer's curiosity. The Osmia loves mystery. She wants a
dark retreat, hidden from the eye. I would like, nevertheless, to
watch her in the privacy of her home and to witness her work with the
same facility as if she were nest-building in the open air. Perhaps
there are some interesting characteristics to be picked up in the
depths of her retreats. It remains to be seen whether my wish can be
realized.
When studying the insect's mental capacity, especially its very
retentive memory for places, I was led to ask myself whether it would
not be possible to make a suitably-chosen Bee build in any place that
I wished, even in my study. And I wanted, for an experiment of this
sort, not an individual but a numerous colony. My preference leant
towards the Three-horned Osmia, who is very plentiful in my
neighbourhood, where, together with Latreille's Osmia, she frequents
in particular the monstrous nests of the Chalicodoma of the Sheds. I
therefore thought out a scheme for making the Three-horned Osmia
accept my study as her settlement and build her nests in glass tubes,
through which I could easily watch the progress. To these crystal
galleries, which might well inspire a certain distrust, were to be
added more natural retreats: reeds of every length and thickness and
disused Chalicodoma-cells taken from among the biggest and the
smallest. A scheme like this sounds mad. I admit it, while mentioning
that perhaps none ever succeeded so well with me. We shall see as
much presently.
My method is extremely simple. All I ask is that the birth of my
insects, that is to say, their first seeing the light, their emerging
from the cocoon, should take place on the spot where I propose to
make them settle. Here there must be retreats of no matter what
nature, but of a shape similar to that in which the Osmia delights.
The first impressions of sight, which are the most long-lived of any,
shall bring back my insects to the place of their birth. And not only
will the Osmiae return, through the always open windows, but they
will always nidify on the natal spot if they find something like the
necessary conditions.
And so, all through the winter, I collect Osmia-cocoons, picked up in
the nests of the Mason-bee of the Sheds; I go to Carpentras to glean
a more plentiful supply in the nests of the Hairy-footed Anthophora,
that old acquaintance whose wonderful cities I used to undermine when
I was studying the history of the Oil-beetles. (This study is not yet
translated into English; but cf. "The Life of the Fly": chapters 2
and 4.--Translator's Note.) Later, at my request, a pupil and
intimate friend of mine, M. Henri Devillario, president of the civil
court at Carpentras, sends me a case of fragments broken off the
banks frequented by the Hairy-footed Anthophora and the Anthophora of
the Walls, useful clods which furnish a handsome adjunct to my
collection. Indeed, at the end, I find myself with handfuls of
cocoons of the Three-horned Osmia. To count them would weary my
patience without serving any particular purpose.
I spread out my stock in a large open box on a table which receives a
bright diffused light but not the direct rays of the sun. The table
stands between two windows facing south and overlooking the garden.
When the moment of hatching comes, those two windows will always
remain open to give the swarm entire liberty to go in and out as it
pleases. The glass tubes and the reed-stumps are laid here and there,
in fine disorder, close to the heap of cocoons and all in a
horizontal position, for the Osmia will have nothing to do with
upright reeds. The hatching of some of the Osmiae will therefore take
place under cover of the galleries destined to be the building-yard
later; and the site will be all the more deeply impressed on their
memory. When I have made these comprehensive arrangements, there is
nothing more to be done; and I wait patiently for the building-season
to open.
My Osmiae leave their cocoons in the second half of April. Under the
immediate rays of the sun, in well-sheltered nooks, the hatching
would occur a month earlier, as we can see from the mixed population
of the snowy almond-tree. The constant shade in my study has delayed
the awakening, without, however, making any change in the nesting-
period, which synchronizes with the flowering of the thyme. We now
have, around my working-table, my books, my jars and my various
appliances, a buzzing crowd that goes in and out of the windows at
every moment. I enjoin the household henceforth not to touch a thing
in the insects' laboratory, to do no more sweeping, no more dusting.
They might disturb the swarm and make it think that my hospitality
was not to be trusted. I suspect that the maid, wounded in her self-
esteem at seeing so much dust accumulating in the master's study, did
not always respect my prohibitions and came in stealthily, now and
again, to give a little sweep of the broom. At any rate, I came
across a number of Osmiae who seemed to have been crushed under foot
while taking a sunbath on the floor in front of the window. Perhaps
it was I myself who committed the misdeed in a heedless moment. There
is no great harm done, for the population is a numerous one; and,
notwithstanding those crushed by inadvertence, notwithstanding the
parasites wherewith many of the cocoons are infested, notwithstanding
those who may have come to grief outside or been unable to find their
way back, notwithstanding the deduction of one-half which we must
make for the males: notwithstanding all this, during four or five
weeks I witness the work of a number of Osmiae which is much too
large to allow of my watching their individual operations. I content
myself with a few, whom I mark with different-coloured spots to
distinguish them; and I take no notice of the others, whose finished
work will have my attention later.
The first to appear are the males. If the sun is bright, they flutter
around the heap of tubes as if to take careful note of the locality;
blows are exchanged and the rival swains indulge in mild skirmishing
on the floor, then shake the dust off their wings and fly away. I
find them, opposite my window, in the refreshment-bar of the lilac-
bush, whose branches bend with the weight of their scented panicles.
Here the Bees get drunk with sunshine and draughts of honey. Those
who have had their fill come home and fly assiduously from tube to
tube, placing their heads in the orifices to see if some female will
at last make up her mind to emerge.
One does, in point of fact. She is covered with dust and has the
disordered toilet that is inseparable from the hard work of the
deliverance. A lover has seen her, so has a second, likewise a third.
All crowd round her. The lady responds to their advances by clashing
her mandibles, which open and shut rapidly, several times in
succession. The suitors forthwith fall back; and they also, no doubt
to keep up their dignity, execute savage mandibular grimaces. Then
the beauty retires into the arbour and her wooers resume their places
on the threshold. A fresh appearance of the female, who repeats the
play with her jaws; a fresh retreat of the males, who do the best
they can to flourish their own pincers. The Osmiae have a strange way
of declaring their passion: with that fearsome gnashing of their
mandibles, the lovers look as though they meant to devour each other.
It suggests the thumps affected by our yokels in their moments of
gallantry.
The ingenious idyll is soon over. By turns greeting and greeted with
a clash of jaws, the female leaves her gallery and begins impassively
to polish her wings. The rivals rush forward, hoist themselves on top
of one another and form a pyramid of which each struggles to occupy
the base by toppling over the favoured lover. He, however, is careful
not to let go; he waits for the strife overhead to calm down; and,
when the supernumeraries realize that they are wasting their time and
throw up the game, the couple fly away far from the turbulent rivals.
This is all that I have been able to gather about the Osmia's
nuptials.
The females, who grow more numerous from day to day, inspect the
premises; they buzz outside the glass galleries and the reed
dwellings; they go in, stay for a while, come out, go in again and
then fly away briskly into the garden. They return, first one, then
another. They halt outside, in the sun, on the shutters fastened back
against the wall; they hover in the window-recess, come inside, go to
the reeds and give a glance at them, only to set off again and to
return soon after. Thus do they learn to know their home, thus do
they fix their birthplace in their memory. The village of our
childhood is always a cherished spot, never to be effaced from our
recollection. The Osmia's life endures for a month; and she acquires
a lasting remembrance of her hamlet in a couple of days. 'Twas there
that she was born; 'twas there that she loved; 'tis there that she
will return. Dulces reminiscitur Argos.
('Now falling by another's wound, his eyes
He casts to heaven, on Argos thinks and dies.'
--"Aeneid," Book 10 Dryden's translation.)
At last each has made her choice. The work of construction begins;
and my expectations are fulfilled far beyond my wishes. The Osmiae
build nests in all the retreats which I have placed at their
disposal. The glass tubes, which I cover with a sheet of paper to
produce the shade and mystery favourable to concentrated toil, do
wonderfully well. All, from first to last, are occupied. The Osmiae
quarrel for the possession of these crystal palaces, hitherto unknown
to their race. The reeds and the paper tubes likewise do wonderfully.
The number provided is too small; and I hasten to increase it. Snail-
shells are recognized as excellent abodes, though deprived of the
shelter of the stone-heap; old Chalicodoma-nests, down to those of
the Chalicodoma of the Shrubs (Cf. "The Mason-bees": chapters 4 and
10.--Translator's Note.), whose cells are so small, are eagerly
occupied. The late-comers, finding nothing else free, go and settle
in the locks of my table-drawers. There are daring ones who make
their way into half-open boxes containing ends of glass tubes in
which I have stored my most recent acquisitions: grubs, pupae and
cocoons of all kinds, whose evolution I wished to study. Whenever
these receptacles have an atom of free space, they claim the right to
build there, whereas I formally oppose the claim. I hardly reckoned
on such a success, which obliges me to put some order into the
invasion with which I am threatened. I seal up the locks, I shut my
boxes, I close my various receptacles for old nests, in short I
remove from the building-yard any retreat of which I do not approve.
And now, O my Osmiae, I leave you a free field!
The work begins with a thorough spring-cleaning of the home. Remnants
of cocoons, dirt consisting of spoilt honey, bits of plaster from
broken partitions, remains of dried Mollusc at the bottom of a shell:
these and much other insanitary refuse must first of all disappear.
Violently the Osmia tugs at the offending object and tears it out;
and then off she goes, in a desperate hurry, to dispose of it far
away from the study. They are all alike, these ardent sweepers: in
their excessive zeal, they fear lest they should block up the place
with a speck of dust which they might drop in front of the new house.
The glass tubes, which I myself have rinsed under the tap, are not
exempt from a scrupulous cleaning. The Osmia dusts them, brushes them
thoroughly with her tarsi and then sweeps them out backwards. What
does she pick up? Not a thing. It makes no difference: as a
conscientious housewife, she gives the place a touch of the broom
nevertheless.
Now for the provisions and the partition-walls. Here the order of the
work changes according to the diameter of the cylinder. My glass
tubes vary greatly in dimensions. The largest have an inner width of
a dozen millimetres (Nearly half an inch.--Translator's Note.); the
narrowest measure six or seven. (About a quarter of an inch.--
Translator's Note.) In the latter, if the bottom suit her, the Osmia
sets to work bringing pollen and honey. If the bottom do not suit
her, if the sorghum-pith plug with which I have closed the rear-end
of the tube be too irregular and badly-joined, the Bee coats it with
a little mortar. When this small repair is made, the harvesting
begins.
In the wider tubes, the work proceeds quite differently. At the
moment when the Osmia disgorges her honey and especially at the
moment when, with her hind-tarsi, she rubs the pollen-dust from her
ventral brush, she needs a narrow aperture, just big enough to allow
of her passage. I imagine that, in a straitened gallery, the rubbing
of her whole body against the sides gives the harvester a support for
her brushing-work. In a spacious cylinder, this support fails her;
and the Osmia starts with creating one for herself, which she does by
narrowing the channel. Whether it be to facilitate the storing of the
victuals or for any other reason, the fact remains that the Osmia
housed in a wide tube begins with the partitioning.
Her division is made by a dab of clay placed at right angles to the
axis of the cylinder, at a distance from the bottom determined by the
ordinary length of a cell. This wad is not a complete round; it is
more crescent-shaped, leaving a circular space between it and one
side of the tube. Fresh layers are swiftly added to the dab of clay;
and soon the tube is divided by a partition which has a circular
opening at the side of it, a sort of dog-hole through which the Osmia
will proceed to knead the Bee-bread. When the victualling is finished
and the egg laid upon the heap, the hole is closed and the filled-up
partition becomes the bottom of the next cell. Then the same method
is repeated, that is to say, in front of the just completed ceiling a
second partition is built, again with a side-passage, which is
stouter, owing to its distance from the centre, and better able to
withstand the numerous comings and goings of the housewife than a
central orifice, deprived of the direct support of the wall, could
hope to be. When this partition is ready, the provisioning of the
second cell is effected; and so on until the wide cylinder is
completely stocked.
The building of this preliminary party-wall, with a narrow, round
dog-hole, for a chamber to which the victuals will not be brought
until later is not restricted to the Three-horned Osmia; it is also
frequently found in the case of the Horned Osmia and of Latreille's
Osmia. Nothing could be prettier than the work of the last-named, who
goes to the plants for her material and fashions a delicate sheet in
which she cuts a graceful arch. The Chinaman partitions his house
with paper screens; Latreille's Osmia divides hers with disks of thin
green cardboard perforated with a serving-hatch which remains until
the room is completely furnished. When we have no glass houses at our
disposal, we can see these little architectural refinements in the
reeds of the hurdles, if we open them at the right season.
By splitting the bramble-stumps in the course of July, we perceive
also that the Three-pronged Osmia, notwithstanding her narrow
gallery, follows the same practice as Latreille's Osmia, with a
difference. She does not build a party-wall, which the diameter of
the cylinder would not permit; she confines herself to putting up a
frail circular pad of green putty, as though to limit, before any
attempt at harvesting, the space to be occupied by the Bee-bread,
whose depth could not be calculated afterwards if the insect did not
first mark out its confines. Can there really be an act of measuring?
That would be superlatively clever. Let us consult the Three-horned
Osmia in her glass tubes.
The Osmia is working at her big partition, with her body outside the
cell which she is preparing. From time to time, with a pellet of
mortar in her mandibles, she goes in and touches the previous ceiling
with her forehead, while the tip of her abdomen quivers and feels the
pad in course of construction. One might well say that she is using
the length of her body as a measure, in order to fix the next ceiling
at the proper distance. Then she resumes her work. Perhaps the
measure was not correctly taken; perhaps her memory, a few seconds
old, has already become muddled. The Bee once more ceases laying her
plaster and again goes and touches the front wall with her forehead
and the back wall with the tip of her abdomen. Looking at that body
trembling with eagerness, extended to its full length to touch the
two ends of the room, how can we fail to grasp the architect's grave
problem? The Osmia is measuring; and her measure is her body. Has she
quite done, this time? Oh dear no! Ten times, twenty times, at every
moment, for the least particle of mortar which she lays, she repeats
her mensuration, never being quite certain that her trowel is going
just where it should.
Meanwhile, amid these frequent interruptions, the work progresses and
the partition gains in width. The worker is bent into a hook, with
her mandibles on the inner surface of the wall and the tip of her
abdomen on the outer surface. The soft masonry stands between the two
points of purchase. The insect thus forms a sort of rolling-press, in
which the mud wall is flattened and shaped. The mandibles tap and
furnish mortar; the end of the abdomen also pats and gives brisk
trowel-touches. This anal extremity is a builder's tool; I see it
facing the mandibles on the other side of the partition, kneading and
smoothing it all over, flattening the little lump of clay. It is a
singular implement, which I should never have expected to see used
for this purpose. It takes an insect to conceive such an original
idea, to do mason's work with its behind! During this curious
performance, the only function of the legs is to keep the worker
steady by spreading out and clinging to the walls of the tunnel.
The partition with the hole in it is finished. Let us go back to the
measuring of which the Osmia was so lavish. What a magnificent
argument in favour of the reasoning-power of animals! To find
geometry, the surveyor's art, in an Osmia's tiny brain! An insect
that begins by taking the measurements of the room to be constructed,
just as any master-builder might do! Why, it's splendid, it's enough
to cover with confusion those horrible sceptics who persist in
refusing to admit the animal's 'continuous little flashes of atoms of
reason!'
O common-sense, veil your face! It is with this gibberish about
continuous flashes of atoms of reason that men pretend to build up
science to-day! Very well, my masters; the magnificent argument with
which I am supplying you lacks but one little detail, the merest
trifle: truth! Not that I have not seen and plainly seen all that I
am relating; but measuring has nothing to do with the case. And I can
prove it by facts.
If, in order to see the Osmia's nest as a whole, we split a reed
lengthwise, taking care not to disturb its contents; or, better
still, if we select for examination the string of cells built in a
glass tube, we are forthwith struck by one detail, namely, the uneven
distances between the partitions, which are placed almost at right
angles to the axis of the cylinder. It is these distances which fix
the size of the chambers, which, with a similar base, have different
heights and consequently unequal holding-capacities. The bottom
partitions, the oldest, are farther apart; those of the front part,
near the orifice, are closer together. Moreover, the provisions are
plentiful in the loftier cells, whereas they are niggardly and
reduced to one-half or even one-third in the cells of lesser height.
Here are a few examples of these inequalities. A glass tube with a
diameter of 12 millimetres (.468 inch.--Translator's Note.), inside
measurement, contains ten cells. The five lower ones, beginning with
the bottom-most, have as the respective distances between their
partitions, in millimetres:
11, 12, 16, 13, 11. (.429, .468, .624, .507, .429 inch.--Translator's
Note.)
The five upper ones measure between their partitions:
7, 7, 5, 6, 7. (.273, .273, .195, .234, .273 inch.--Translator's
Note.)
A reed-stump 11 millimetres (.429 inch.--Translator's Note.) across
the inside contains fifteen cells; and the respective distances
between the partitions of those cells, starting from the bottom, are:
13, 12, 12, 9, 9, 11, 8, 8, 7, 7, 7, 6, 6, 6, 7. (.507, .468, .468,
.351, .351, .429, .312, .312, .273, .273, .273, .234, .234, .234,
.273 inch.--Translator's Note.)
When the diameter of the tunnel is less, the partitions can be still
further apart, though they retain the general characteristic of being
closer to one another the nearer they are to the orifice. A reed of
five millimetres (.195 inch.--Translator's Note.) in diameter, gives
me the following distances, always starting from the bottom:
22, 22, 20, 20, 12, 14. (.858, .858, .78, .78, .468, .546 inch.--
Translator's Note.)
Another, of 9 millimetres (.351 inch.--Translator's Note.), gives me:
15, 14, 11, 10, 10, 9, 10. (.585, .546, .429, .39, .39, .351, .39
inch.--Translator's Note.)
A glass tube of 8 millimetres (.312 inch.--Translator's Note.)
yields:
15, 14, 20, 10, 10, 10. (.585, .546, .78, .39, .39, .39 inch.--
Translator's Note.).
I could fill pages and pages with such figures, if I cared to print
all my notes. Do they prove that the Osmia is a geometrician,
employing a strict measure based on the length of her body? Certainly
not, because many of those figures exceed the length of the insect;
because sometimes a higher number follows suddenly upon a lower;
because the same string contains a figure of one value and another
figure of but half that value. They prove only one thing: the marked
tendency of the insect to shorten the distance between the party-
walls as the work proceeds. We shall see later that the large cells
are destined for the females and the small ones for the males.
Is there not at least a measuring adapted to each sex? Again, not so;
for in the first series, where the females are housed, instead of the
interval of 11 millimetres, which occurs at the beginning and the
end, we find, in the middle of the series, an interval of 16
millimetres, while in the second series, reserved for the males,
instead of the interval of 7 millimetres at the beginning and the
end, we have an interval of 5 millimetres in the middle. It is the
same with the other series, each of which shows a striking
discrepancy in its figures. If the Osmia really studied the
dimensions of her chambers and measured them with the compasses of
her body, how could she, with her delicate mechanism, fail to notice
mistakes of 5 millimetres, almost half her own length?
Besides, all idea of geometry vanishes if we consider the work in a
tube of moderate width. Here, the Osmia does not fix the front
partition in advance; she does not even lay its foundation. Without
any boundary-pad, with no guiding mark for the capacity of the cell,
she busies herself straightway with the provisioning. When the heap
of Bee-bread is judged sufficient, that is, I imagine, when her tired
body tells her that she has done enough harvesting, she closes up the
chamber. In this case, there is no measuring; and yet the capacity of
the cell and the quantity of the victuals fulfil the regular
requirements of one or the other sex.
Then what does the Osmia do when she repeatedly stops to touch the
front partition with her forehead and the back partition, the one in
the course of building, with the tip of her abdomen? I have no idea
what she does or what she has in view. I leave the interpretation of
this performance to others, more venturesome than I. Plenty of
theories are based on equally shaky foundations. Blow on them and
they sink into the quagmire of oblivion.
The laying is finished, or perhaps the cylinder is full. A final
partition closes the last cell. A rampart is now built, at the
orifice of the tube itself, to forbid the ill-disposed all access to
the home. This is a thick plug, a massy work of fortification,
whereon the Osmia spends enough mortar to partition off any number of
cells. A whole day is not too long for making this barricade,
especially in view of the minute finishing-touches, when the Osmia
fills up with putty every chink through which the least atom could
slip. The mason completing a wall smooths his plaster and brings it
to a fine surface while it is still wet; the Osmia does the same, or
almost. With little taps of the mandibles and a continual shaking of
her head, a sign of her zest for the work, she smooths and polishes
the surface of the lid for hours at a time. After such pains, what
foe could visit the dwelling?
And yet there is one, an Anthrax, A. sinuata (Cf. "The Life of the
Fly": chapters 2 and 4.--Translator's Note.), who will come later on,
in the height of summer, and succeed, invisible bit of thread that
she is, in making her way to the grub through the thickness of the
door and the web of the cocoon. In many cells, mischief of another
kind has already been done. During the progress of the works, an
impudent Midge, one of the Tachina-flies, who feeds her family on the
victuals amassed by the Bee, hovers in front of the galleries. Does
she penetrate to the cells and lay her eggs there in the mother's
absence? I could never catch the sneak in the act. Does she, like
that other Tachina who ravages cells stocked with game (The cells of
the Hunting Wasps.--Translator's Note.), nimbly deposit her eggs on
the Osmia's harvest at the moment when the Bee is going indoors? It
is possible, though I cannot say for certain. The fact remains that
we soon see the Midge's grub-worms swarming around the larva, the
daughter of the house. There are ten, fifteen, twenty or more of them
gnawing with their pointed mouths at the common dish and turning the
food into a heap of fine, orange-coloured vermicelli. The Bee's grub
dies of starvation. It is life, life in all its ferocity even in
these tiny creatures. What an expenditure of ardent labour, of
delicate cares, of wise precautions, to arrive at...what? Her
offspring sucked and drained dry by the hateful Anthrax; her family
sweated and starved by the infernal Tachina.
The victuals consist mostly of yellow flour. In the centre of the
heap, a little honey is disgorged, which turns the pollen-dust into a
firm, reddish paste. On this paste the egg is laid, not flat, but
upright, with the fore-end free and the hind-end lightly held and
fixed in the plastic mass. When hatched, the young grub, kept in its
place by its rear-end, need only bend its neck a little to find the
honey-soaked paste under its mouth. When it grows stronger, it will
release itself from its support and eat up the surrounding flour.
All this is touching, in its maternal logic. For the new-born, dainty
bread-and-honey; for the adolescent, dry bread. In cases where the
provisions are all of a kind, these delicate precautions are
superfluous. The victuals of the Anthophorae and the Chalicodomae
consist of flowing honey, the same throughout. The egg is then laid
at full length on the surface, without any particular arrangement,
thus compelling the new-born grub to take its first mouthfuls at
random. This has no drawback, as the food is of the same quality
throughout. But, with the Osmia's provisions--dry powder on the
edges, jam in the centre--the grub would be in danger if its first
meal were not regulated in advance. To begin with pollen not seasoned
with honey would be fatal to its stomach. Having no choice of its
mouthfuls because of its immobility and being obliged to feed on the
spot where it was hatched, the young grub must needs be born on the
central mass, where it has only to bend its head a little way in
order to find what its delicate stomach calls for. The place of the
egg, therefore, fixed upright by its base in the middle of the red
jam, is most judiciously chosen. What a contrast between this
exquisite maternal forethought and the horrible destruction by the
Anthrax and the Midge!
The egg is rather large for the size of the Osmia. It is cylindrical,
slightly curved, rounded at both ends and transparent. It soon
becomes cloudy, while remaining diaphanous at each extremity. Fine
lines, hardly perceptible to the most penetrating lens, show
themselves in transverse circles. These are the first signs of
segmentation. A contraction appears in the front hyaline part,
marking the head. An extremely thin opaque thread runs down either
side. This is the cord of tracheae communicating between one
breathing-hole and another. At last, the segments show distinctly,
with their lateral pads. The grub is born.
At first, one would think that there was no hatching in the proper
sense of the word--that is to say, no bursting and casting of a
wrapper. The most minute attention is necessary to show that
appearances are deceptive and that actually a fine membrane is thrown
off from front to back. This infinitesimal shred is the shell of the
egg.
The grub is born. Fixed by its base, it curves into an arc and bends
its head, until now held erect, down to the red mass. The meal
begins. Soon a yellow cord occupying the front two-thirds of the body
proclaims that the digestive apparatus is swelling out with food. For
a fortnight, consume your provender in peace, my child; then spin
your cocoon: you are now safe from the Tachina! Shall you be safe
from the Anthrax' sucker later on? Alack!
CHAPTER 3. THE DISTRIBUTION OF THE SEXES.
Does the insect know beforehand the sex of the egg which it is about
to lay? When examining the stock of food in the cells just now, we
began to suspect that it does, for each little heap of provisions is
carefully proportioned to the needs at one time of a male and at
another of a female. What we have to do is to turn this suspicion
into a certainty demonstrated by experiment. And first let us find
out how the sexes are arranged.
It is not possible to ascertain the chronological order of a laying,
except by going to suitably-chosen species. Digging up the burrows of
Cerceris-, Bembex- or Philanthus-wasps will never tell us that this
grub has taken precedence of that in point of time nor enable us to
decide whether one cocoon in a colony belongs to the same family as
another. To compile a register of births is absolutely impossible
here. Fortunately there are a few species in which we do not find
this difficulty: these are the Bees who keep to one gallery and build
their cells in storeys. Among the number are the different
inhabitants of the bramble-stumps, notably the Three-pronged Osmiae,
who form an excellent subject for observation, partly because they
are of imposing-size--bigger than any other bramble-dwellers in my
neighbourhood--partly because they are so plentiful.
Let us briefly recall the Osmia's habits. Amid the tangle of a hedge,
a bramble-stalk is selected, still standing, but a mere withered
stump. In this the insect digs a more or less deep tunnel, an easy
piece of work owing to the abundance of soft pith. Provisions are
heaped up right at the bottom of the tunnel and an egg is laid on the
surface of the food: that is the first-born of the family. At a
height of some twelve millimetres (About half an inch.--Translator's
Note.), a partition is fixed, formed of bramble saw-dust and of a
green paste obtained by masticating particles of the leaves of some
plant that has not yet been identified. This gives a second storey,
which in its turn receives provisions and an egg, the second in order
of primogeniture. And so it goes on, storey by storey, until the
cylinder is full. Then a thick plug of the same green material of
which the partitions are formed closes the home and keeps out
marauders.
In this common cradle, the chronological order of births is perfectly
clear. The first-born of the family is at the bottom of the series;
the last-born is at the top, near the closed door. The others follow
from bottom to top in the same order in which they followed in point
of time. The laying is numbered automatically; each cocoon tells us
its respective age by the place which it occupies.
To know the sexes, we must wait for the month of June. But it would
be unwise to postpone our investigations until that period. Osmia-
nests are not so common that we can hope to pick one up each time
that we go out with that object; besides, if we wait for the
hatching-period before examining the brambles, it may happen that the
order has been disturbed through some insects' having tried to make
their escape as soon as possible after bursting their cocoons; it may
happen that the male Osmiae, who are more forward than the females,
are already gone. I therefore set to work a long time beforehand and
devote my leisure in winter to these investigations.
The bramble-sticks are split and the cocoons taken out one by one and
methodically transferred to glass tubes, of approximately the same
diameter as the native cylinder. These cocoons are arranged one on
top of the other in exactly the same order that they occupied in the
bramble; they are separated from one another by a cotton plug, an
insuperable obstacle to the future insect. There is thus no fear that
the contents of the cells may become mixed or transposed; and I am
saved the trouble of keeping a laborious watch. Each insect can hatch
at its own time, in my presence or not: I am sure of always finding
it in its place, in its proper order, held fast fore and aft by the
cotton barrier. A cork or sorghum-pith partition would not fulfil the
same purpose: the insect would perforate it and the register of
births would be muddled by changes of position. Any reader wishing to
undertake similar investigations will excuse these practical details,
which may facilitate his work.
We do not often come upon complete series, comprising the whole
laying, from the first-born to the youngest. As a rule, we find part
of a laying, in which the number of cocoons varies greatly, sometimes
falling as low as two, or even one. The mother has not deemed it
advisable to confide her whole family to a single bramble-stump; in
order to make the exit less toilsome, or else for reasons which
escape me, she has left the first home and elected to make a second
home, perhaps a third or more.
We also find series with breaks in them. Sometimes, in cells
distributed at random, the egg has not developed and the provisions
have remained untouched, but mildewed; sometimes, the larva has died
before spinning its cocoon, or after spinning it. Lastly, there are
parasites, such as the Unarmed Zonitis (Zonitis mutica, one of the
Oil-beetles.--Translator's Note.) and the Spotted Sapyga (A Digger-
wasp.--Translator's Note.), who interrupt the series by substituting
themselves for the original occupant. All these disturbing factors
make it necessary to examine a large number of nests of the Three-
pronged Osmia, if we would obtain a definite result.
I have been studying the bramble-dwellers for seven or eight years
and I could not say how many strings of cocoons have passed through
my hands. During a recent winter, in view particularly of the
distribution of the sexes, I collected some forty of this Osmia's
nests, transferred their contents into glass tubes and made a careful
summary of the sexes. I give some of my results. The figures start in
their order from the bottom of the tunnel dug in the bramble and
proceed upwards to the orifice. The figure 1 therefore denotes the
first-born of the series, the oldest in date; the highest figure
denotes the last-born. The letter M, placed under the corresponding
figure, represents the male and the letter F the female sex.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
F F M F M F M M F F F F M F M
This is the longest series that I have ever been able to procure. It
is also complete, inasmuch as it comprises the entire laying of the
Osmia. My statement requires explaining, otherwise it would seem
impossible to know whether a mother whose acts one has not watched,
nay more, whom one has never seen, has or has not finished laying her
eggs. The bramble-stump under consideration leaves a free space of
nearly four inches above the continuous string of cocoons. Beyond it,
at the actual orifice, is the terminal stopper, the thick plug which
closes the entrance to the gallery. In this empty portion of the
tunnel there is ample accommodation for numerous cocoons. The fact
that the mother has not made use of it proves that her ovaries were
exhausted; for it is exceedingly unlikely that she has abandoned
first-rate lodgings to go laboriously digging a new gallery elsewhere
and there continue her laying.
You may say that, if the unoccupied space marks the end of the
laying, nothing tells us that the beginning is actually at the bottom
of the cul-de-sac, at the other end of the tunnel. You may also say
that the laying is done in shifts, separated by intervals of rest.
The space left empty in the channel would mean that one of these
shifts was finished and not that there were no more eggs ripe for
hatching. In answer to these very plausible explanations, I will say
that, the sum of my observations--and they have been extremely
numerous--is that the total number of eggs laid not only by the
Osmiae but by a host of other Bees fluctuates round about fifteen.
Besides, when we consider that the active life of these insects lasts
hardly a month; when we remember that this period of activity is
disturbed by dark, rainy or very windy days, during which all work is
suspended; when lastly we ascertain, as I have done ad nauseam in the
case of the Three-horned Osmia, the time required for building and
victualling a cell, it becomes obvious that the total laying must be
kept within narrow bounds and that the mother has no time to lose if
she wishes to get fifteen cells satisfactorily built in three or four
weeks interrupted by compulsory rests. I shall give some facts later
which will dispel your doubts, if any remain.
I assume, therefore, that a number of eggs bordering on fifteen
represents the entire family of an Osmia, as it does of many other
Bees.
Let us consult some other complete series. Here are two:
1 2 3 4 5 6 7 8 9 10 11 12 13
F F M F M F M F F F F M F
F M F F F M F F M F M
In both cases, the laying is taken as complete, for the same reasons
as above.
We will end with some series that appear to me incomplete, in view of
the small number of cells and the absence of any free space above the
pile of cocoons:
1 2 3 4 5 6 7 8
M M F M M M M M
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