German by _Blassiere_, there is printed a letter from M. Schirach to
you, dated 15 April 1771, where he speaks of some hives, in which the
whole brood changed into drones. You will remember that he ascribes this
circumstance to some unknown vice in the ovaries of the queen; but he
was far from suspecting that retarded fecundation had been the cause of
vitiation. He justly felicitated himself on discovering a method to
prevent the destruction of hives in this situation, which was simple,
for it consisted in removing the queen that laid the eggs of males only,
and substituting one for her whose ovaries were not impaired. But to
make the substitution effectual, it was necessary to procure queens at
pleasure; a secret reserved for M. Schirach, and of which I shall speak
in the following letter. You observe that the whole experiments of the
German naturalist tended to the preservation of the hives whose queens
laid none except male eggs; and that he did not attempt to discover the
cause of the vice evident in their ovaries.
M. de Reaumur also says a few words, somewhere, of a hive containing
many more drones than workers, but advances no conjectures on the cause.
However, he adds, as a remarkable circumstance, that the males were
tolerated in this hive until the subsequent spring. It is true that bees
governed by a queen laying only male eggs, or by a virgin queen,
preserve their drones several months after they have been massacred in
other hives. I can ascribe no reason for it, but it is a fact I have
several times witnessed during my long course of observations on
retarded impregnation. In general it has appeared that while the queen
lays male eggs, bees do not massacre the males already perfect in the
hive. PREGNY, _21. August 1791_.
FOOTNOTES:
{G} The experiments suggested in this paragraph, recall a singular
reflection of M. de Reaumur. Where treating of oviparous flies, he says,
it would not be impossible for a hen to produce a living chicken, if,
after fecundation, the eggs she should first lay could by any means be
retained twenty-one days in the oviducts. _Mem. sur. les Insect. tom. 4.
mem. 10._
LETTER IV.
_ON M. SCHIRACH'S DISCOVERY._
When you found it necessary, Sir, in the new edition of your works, to
give an account of M. Schirach's beautiful experiments on the conversion
of common worms into royal ones, you invited naturalists to repeat them.
Indeed such an important discovery required the confirmation of several
testimonies. For this reason, I hasten to inform you that all my
researches establish the reality of the discovery. During ten years
that I have studied bees, I have repeated M. Schirach's experiment so
often, and with such uniform success, that I can no longer have the
least doubt on the subject. Therefore, I consider it an established
fact, when bees lose their queen, and several workers' worms are
preserved in the hive, they enlarge some of their cells, and supply them
not only with a different kind of food, but a greater quantity of it,
and the worms reared in this manner, instead of changing to common bees,
become real queens. I request my readers to reflect on the explanation
you have given of so uncommon a fact, and the philosophical consequences
you have deduced from it. _Contemplation de la Nature, part. II, chap.
27._
In this letter I shall content myself with some account of the figure of
the royal cells constructed by bees around those worms that are destined
for the royal state, and terminate with discussing some points wherein
my observations differ from those of M. Schirach.
Bees soon become sensible of having lost their queen, and in a few hours
commence the labour necessary to repair their loss. First, they select
the young common worms, which the requisite treatment is to convert into
queens, and immediately begin with enlarging the cells where they are
deposited. Their mode of proceeding is curious; and the better to
illustrate it, I shall describe the labour bestowed on a single cell,
which will apply to all the rest, containing worms destined for queens.
Having chosen a worm, they sacrifice three of the contiguous cells:
next, they supply it with food, and raise a cylindrical inclosure
around, by which the cell becomes a perfect tube, with a rhomboidal
bottom; for the parts forming the bottom are left untouched. If the bees
damaged it, they would lay open three corresponding cells on the
opposite surface of the comb, and, consequently, destroy their worms,
which would be an unnecessary sacrifice, and Nature has opposed it.
Therefore, leaving the bottom rhomboidal, they are satisfied with
raising a cylindrical tube around the worm, which, like the other cells
in the comb, is horizontal. But this habitation remains suitable to the
worm called to the royal state only during the first three days of its
existence: another situation is requisite for the other two days it is a
worm. Then, which is so small a portion of its life, it must inhabit a
cell nearly of a pyramidal figure, and hanging perpendicularly; we may
say the workers know it; for, after the worm has completed the third
day, they prepare the place to be occupied by its new lodging. They gnaw
away the cells surrounding the cylindrical tube, mercilessly sacrifice
their worms, and use the wax in constructing a new pyramidal tube, which
they solder at right angles to the first, and work it downwards. The
diameter of this pyramid decreases insensibly from the base, which is
very wide, to the point. During the two days that it is inhabited by
the worm, a bee constantly keeps its head more or less inserted into the
cell, and, when this worker quits it, another comes to occupy its place.
In proportion as the worm grows, the bees labour in extending the cell,
and bring food, which they place before its mouth, and around its body,
forming a kind of cord around it. The worm, which can move only in a
spiral direction, turns incessantly to take the food before its head: it
insensibly descends, and at length arrives at the orifice of the cell.
Now is the time of transformation to a nymph. As any farther care is
unnecessary, the bees close the cell with a peculiar substance
appropriated for it, and there the worm undergoes both its
metamorphoses.
Though M. Schirach supposes that none but worms three days old are
selected for the royal treatment, I am certain of the contrary; and that
the operation succeeds equally well on those of two days only. I must
be permitted to relate at length the evidence I have of the fact, which
will both demonstrate the reality of common worms being converted into
queens, and the little influence which their age has on the effect of
the operation.
I put some pieces of comb, with some workers eggs, in the cells, and of
the same kind as those already hatched, into a hive deprived of the
queen. The same day several cells were enlarged by the bees, and
converted into royal cells, and the worms supplied with a thick bed of
jelly. Five were then removed from those cells, and five common worms,
which, forty-eight hours before we had seen come from the egg
substituted for them. The bees did not seem aware of the change; they
watched over the new worms the same as over those chosen by themselves;
they continued enlarging the cells, and closed them at the usual time.
When they had hatched on them seven days{H}, we removed the cells to
see the queens that were to be produced. Two were excluded, almost at
the same moment, of the largest size, and well formed in every respect.
The term of the other cells having elapsed, and no queen appearing, we
opened them. In one, was a dead queen, but still a nymph; the other two
were empty. The worms had spun their silk coccoons, but died before
passing into their nymphine state, and presented only a dry skin. I can
conceive nothing more conclusive than this experiment. It demonstrates
that bees have the power of converting the worms of workers into queens;
since they succeeded in procuring queens, by operating on the worms
which we ourselves had selected. It is equally demonstrated, that the
success of the operation does not depend on the worms being three days
old, as those entrusted to the bees were only two. Nor is this all; bees
can convert worms still younger into queens. The following experiment
showed, that when the queen is lost, they destine worms only a few
hours old to replace her.
I was in possession of a hive, which being long deprived of the female,
had neither egg nor worm. I provided a queen of the greatest fertility;
and she immediately began laying in the cells of workers. I removed this
female before being quite three days in the hive, and before any of her
eggs were hatched. The following morning, that is, the fourth day, we
counted fifty minute worms, the oldest scarcely hatched twenty-four
hours. However, several were already destined for queens, which was
proved by the bees depositing around them a much more abundant provision
of food than is supplied to common worms. Next day, the worms were near
forty hours old: the bees had enlarged and converted their hexagonal
cells into cylindrical ones of the greatest capacity. During the
subsequent days, they still laboured at them, and closed them on the
fifth from the origin of the worms. Seven days after sealing of the
first of these royal cells, a queen of the largest size proceeded from
it. She immediately rushed towards the other royal cells, and
endeavoured to destroy their nymphs and worms. In another letter, I
shall recount the effects of her fury.
From these details, you will observe, Sir, that M. Schirach's
experiments had not been sufficiently diversified when he affirmed that
it was essential for the conversion of common worms into queens, they
should be three days old. It is undoubted, that equal success attends
the experiment not only with worms two days old, but also when they have
been only a few hours in existence.
After my researches to corroborate M. Schirach's discovery, I was
desirous of learning whether, as this observer conceives, the only means
which the bees have of procuring a queen, is giving the common worms a
certain kind of aliment, and rearing them in the largest cells. You
will remember, that M. de Reaumur's sentiments are very different: "The
mother should lay, and she does lay, eggs from which flies fit for being
mothers must in their turn proceed. She does so; and it is evident the
workers know what she is to do. Bees, to which the mother is so
precious, seem to take a peculiar interest in the eggs that one is to
proceed from, and to consider them of the greatest value. They construct
particular cells where they are to be deposited.--The figure of a royal
cell only begun, very much resembles a cup, or, more correctly speaking,
the cup that has lost its acorn."
M. de Reaumur, though he did not suspect the possibility of a common
worm being converted into a queen, conceived that the queen bee laid a
particular species of eggs in the royal cells, from which worms should
come that would be queens. According to M. Schirach, on the other hand,
bees always having the power of procuring a queen by bringing up worms
three days old in a particular manner, it would be needless for nature
to grant females the faculty of laying royal eggs. Such prodigality is,
in his eyes, inconsistent with the ordinary laws of nature. Therefore he
maintains, in direct terms, that she does not lay royal eggs in cells
purposely prepared to receive them. He considers the royal cells only as
common ones, enlarged by the bees at the moment when the included worm
is destined for a queen; and adds, that the royal cell would always be
too long for the belly of the mother to reach the bottom.
I admit that M. de Reaumur no where says he has seen the queen lay in
the royal cell. However he did not doubt the fact; and, after all my
observations, I must esteem his opinion just. It is quite certain that,
at particular periods of the year, the bees prepare royal cells; that
the females deposit their eggs in them; and that worms, which shall
became queens, proceed from these eggs.
M. Schirach's objection, concerning the length of the cells, proves
nothing; for the queen does not delay depositing her egg till they are
finished. While only sketched and shaped like the cup of an acorn, she
lays it. This naturalist, dazzled by the brilliancy of his discovery,
saw only part of the truth. He was the first to find out the resource
granted to bees by nature, for repairing the loss of their queen; and
too soon persuaded himself that she had provided no other resource for
the production of females. This error arose from not observing bees in
very flat hives: had he used such as mine, he would have found, on
opening them in spring, a confirmation of M. de Reaumur's opinion. Then,
which is the season of swarming, hives in good condition are governed by
a very fruitful queen: there are royal cells of a figure widely
different from those constructed around the worms destined by the bees
for queens. They are large, attached to the comb by a stalk, and
hanging vertically like stalactites, such, in short, as M. de Reaumur
has described them. The females lay in them before completion. We have
surprised a queen depositing the egg when the cell was only as the cup
of an acorn. The workers never lengthen them until the egg has been
laid. In proportion as the worm grows, they are enlarged, and closed by
the bees when the first transformation approaches. Thus it is true,
that, in spring, the queen deposits in royal cells, previously prepared,
eggs from which flies of her own species are to come. Nature has,
therefore, provided a double means for the multiplication and
conservation of their race.
_PREGNY, 24. August 1791._
FOOTNOTES:
{H} The author's meaning here is obscure.--T.
LETTER V.
_EXPERIMENTS PROVING THAT THERE ARE SOMETIMES COMMON BEES WHICH LAY
FERTILE EGGS._
The singular discovery of M. Riems, concerning the existence of fertile
workers, has appeared very doubtful to you, Sir. You have suspected that
the eggs ascribed to workers by this naturalist had actually been
produced by small queens, which, on account of their size, were
confounded with common bees. But you do not positively insist that M.
Riems is deceived; and, in the letter which you did me the honour to
address to me, you requested me to investigate, by new experiments,
whether there are actually working bees capable of laying fertile eggs.
I have made these experiments with great care: and it is for you to
judge of the confidence they merit.
On the fifth of August 1788, we found the eggs and worms of large drones
in two hives, which had both been some time deprived of queens. We also
observed the rudiments of some royal cells appended like stalactites to
the edges of the combs. The eggs of males were in them. Being perfectly
secure that there was no queen of large size among the bees of these two
hives, the eggs, which daily became more numerous, were evidently laid
either by queens of small size or by fertile workers. I had reason to
believe it was actually by common bees, for we had frequently observed
them inserting the posterior part into the cells; and assuming the same
attitude as the queen when laying. But, not withstanding every exertion,
we had never been able to seize one in this situation, to examine it
more narrowly. And we were unwilling to assert any thing positively,
without having the bees in our hands that had actually laid. Therefore
our observations were continued with equal assiduity, in hopes that, by
some fortunate chance, or in a moment of address, we could secure one of
them. More than a month all our endeavours were abortive.
My assistant then offered to perform an operation that required both
courage and patience, and which I could not resolve to suggest, though
the same expedient had occurred to myself. He proposed to examine each
bee in the hive separately, to discover whether some small queen had not
insinuated herself among them, and escaped our first researches. This
was an important experiment; for, should no small queen be found, it
would be demonstrative evidence that the eggs had been laid by simple
workers.
To perform this operation with all possible exactness, immersing the
bees was not enough. You know, Sir, that the contact of water stiffens
their organs, that it produces a certain alteration of their external
figure: and, from the resemblance of small queens to workers, the
slightest alteration of shape would prevent us from distinguishing with
sufficient accuracy to what species those immersed might belong.
Therefore it was necessary to seize the whole bees of both hives,
notwithstanding their irritation, and examine their specific character
with the utmost care. This my assistant undertook, and executed with
great address. Eleven days were employed in it; and, during all that
time, he scarcely allowed himself any relaxation, but what the relief of
his eyes required. He took every bee in his hand; he attentively
examined the trunk, the hind limbs, and the sting: there was not one
without the characteristics of the common bee, that is, the little
basket on the hind legs, the long trunk, and the straight sting. He had
previously prepared glass cases containing combs. Into these, he put
each bee after examination. It is superfluous to observe they were
confined, which was a precaution indispensible until termination of the
experiment. Neither was it enough to establish that the whole were
workers; we had also to continue the experiment, and observe whether any
would produce eggs. Thus we examined the cells for several days, and
soon observed new laid eggs, from which the worms of drones came at the
proper time. My assistant held in his hands the bees that produced them;
and as he was perfectly certain they were common ones, it is proved that
there are sometimes fertile workers in hives.
Having ascertained M. Schirach's discovery, by so decisive an
experiment, we replaced all the bees examined, in very thin glass hives,
being only eighteen lines thick, and capable of containing but a single
row of combs, and thus were extremely favourable to the observer. We
thought, by strictly persisting to watch the bees, we might surprise a
fertile one in the act of laying, seize and dissect her. This we were
desirous of doing, for the purpose of comparing her ovaries with those
of queens, and to ascertain the difference. At length, on the eighth of
September, we had the good fortune to succeed.
A bee appeared in the position of a female laying. Before she had time
to leave the cell, we suddenly opened the hive and seized her. She
presented all the external characteristics of common bees; the only
difference we could recognise, and that was a very slight one, consisted
in the belly seeming less and more slender than that of workers. On
dissection, her ovaries were found more fragile, smaller and composed of
fewer oviducts than the ovaries of queens. The filaments containing the
eggs were extremely fine, and exhibited swellings at equal distances. We
counted eleven eggs of sensible size, some of which appeared ripe for
laying. This ovary was double like that of queens.
On the ninth of September, we seized another fertile worker the instant
she laid, and dissected her. The ovary was still less expanded than that
of the preceding bee, and only four eggs had attained maturity. My
assistant extracted one from the oviducts, and succeeded in fixing it by
an end on a glass slider. We may take this opportunity of remarking,
that it is in the oviducts themselves the eggs are imbued with the
viscous liquid, with which they are produced, and not in passing through
the spherical sac as Swammerdam believed. During the remainder of this
month, we found ten fertile workers in the same hives, and dissected
them all. In most, the ovaries were easily distinguished, but in some we
could not discern the faintest traces of them. In these last, the
oviducts to all appearance were but imperfectly developed, and more
address than we had acquired in dissection was necessary to distinguish
them.
Fertile workers never lay the eggs of common bees; they produce none but
those of males. M. Riems had already observed this singular fact; and
here all my observations correspond with his. I shall only add to what
he says, that fertile workers are not absolutely indifferent in the
choice of cells for depositing their eggs. They always prefer large
ones; and only use small cells when unable to find those of larger
diameter. But they so far correspond with queens whose impregnation has
been retarded, that they sometimes lay in royal cells.
Speaking of females laying male eggs alone, I have already expressed my
surprise that bees bestow, on those deposited in royal cells, such care
and attention as to feed the worms proceeding from them, and, at the
period of transformation, to close them up. But I know not, Sir, why I
omitted to observe that, after sealing the royal cells, the workers
build them up, and sit on them until the last metamorphosis of the
included male{I}. The treatment of the royal cells where fertile workers
lay the eggs of drones is very different. They begin indeed with
bestowing every care on their eggs and worms; they close the cells at a
suitable time, but never fail to destroy them three days afterwards.
Having finished these first experiments with success, I had still to
discover the cause of the expansion of the sexual organs of fertile
workers. M. Riems had not engaged in this interesting problem; and at
first I dreaded that I should have no other guide towards its solution
than conjecture. Yet from serious reflection, it appeared, that, by
connecting the facts contained in this letter, there was some light that
might elucidate my procedure in this new research.
From M. Schirach's elegant discoveries, it is beyond all doubt that
common bees are originally of the female sex. They have received from
nature the germs of an ovary, but she has allowed its expansion only in
the particular case of their receiving a certain aliment while a worm.
Thus it must be the peculiar object of inquiry whether the fertile
workers get that aliment while worms.
All my experiments convince me that bees, capable of laying, are
produced in hives that have lost the queen. A great quantity of royal
jelly is then prepared for feeding the larvæ destined to replace her.
Therefore, if fertile workers are produced in this situation alone, it
is evident their origin is only in those hives where bees prepare the
royal jelly. Towards this circumstance, I bent all my attention. It
induced me to suspect that when bees give the _royal treatment_ to
certain worms, they either by accident or a particular instinct, the
principle of which is unknown to me, drop some particles of royal jelly
into cells contiguous to those containing the worms destined for queens.
The larvæ of workers that have accidentally received portions of so
active an aliment, must be more or less affected by it; and their
ovaries should acquire a degree of expansion. But this expansion will be
imperfect; why? because the royal food has been administered only in
small portions, and, besides, the larvæ having lived in cells of the
smallest dimensions, their parts cannot extend beyond the ordinary
proportions. Thus, the bees produced by them will resemble common
workers in size and all the external characteristics. Added to that,
they will have the faculty of laying some eggs, solely from the effect
of the trifling portion of royal jelly mixed with their aliment.
That we may judge of the justness of this explanation, it is necessary
to consider fertile workers from their origin; to investigate whether
the cells, where they are brought up, are constantly in the vicinity of
the royal cells, and if their food is mixed with particles of the royal
jelly. Unfortunately, the execution of these experiments is very
difficult. When pure, the royal jelly is recognised by its sharp and
pungent taste; but, when mixed with other substances, the peculiar
savour is very imperfectly distinguished. Thus I conceived, that my
investigation should be limited to the situation of the cells; and, as
the subject is important, permit me to enter a little into detail{J}.