more I reflected on it, the more did it seem inexplicable. At length, by
attentively meditating on the circumstances of the experiment it
appeared there were two principles, the influence of which I should
first of all endeavour to appreciate separately. On the one hand, this
queen had suffered long confinement; on the other, her fecundation had
been extremely retarded. You know, Sir, that queens generally receive
the males about the fifth or sixth day, and this queen had not copulated
until the thirty-sixth. Little weight could be given to the supposition,
that the peculiarity could be occasioned by confinement. Queens, in the
natural state, leave their hives only once to seek the males. All the
rest of their life they remain voluntary prisoners. Thus, it was
improbable that captivity could produce the effect I wished to explain.
At the same time, as it was essential to neglect nothing in a subject so
new, I wished to ascertain whether it was owing to the length of
confinement, or to retarded fecundation.
Investigating this was no easy matter. To discover whether captivity,
and not retarded fecundation, vitiated the ovaries, it was necessary to
allow a female to receive the approaches of a male, and also to keep her
imprisoned. Now this could not be, for bees never copulate in hives. On
the same account, it was impossible to retard the copulation of a queen
without keeping her in confinement. I was long embarrassed by the
difficulty. At length, I contrived an apparatus, which, though
imperfect, nearly fulfilled my purpose.
I put a queen, at the moment of her last metamorphosis, into a hive well
stored, and sufficiently provided with workers and males; the entrance
was contracted so as to prevent her exit, but allowed free passage to
the workers. I also made another opening for the queen, and adapted a
glass tube to it, communicating with a cubical glass box eight feet
high. Hither the queen could at all times come and fly about, enjoying a
purer air than was to be found within the hive; but she could not be
fecundated; for though the males flew about within the same bounds, the
space was too limited to admit of any union between them. By the
experiments related in my first letter, copulation takes place high in
the air only: therefore, in this apparatus, I found the advantage of
retarding fecundation, while the liberty the queen now had, did not
render her situation too remote from the natural state. I attended to
the experiment fifteen days. Every fine morning, the young captive left
her hive; she traversed her glass prison, and flew much about, and with
great facility. She laid none during this interval, for she had not
united with a male. On the sixteenth day, I set her at liberty: she left
the hive, rose aloft in the air, and soon returned with full evidence of
impregnation. In two days, she laid, first the eggs of workers, and
afterwards as many as the most fertile queens.
It thence followed, 1. That captivity did not alter the organs of
queens. 2. When fecundation took place within the first sixteen days,
she produced both species of eggs.
This was an important experiment. It rendered my labours much more
simple, by clearly pointing out the method to be pursued: it absolutely
precluded the supposed influence of captivity; and left nothing for
investigation but the consequences of retarded fecundation.
With this view, I repeated the experiment; but, instead of giving the
virgin queen liberty on the sixteenth day, I retained her until the
twenty-first. She departed, rose high in the air, was fecundated, and
returned. Thirty-six hours afterwards, she began to lay: but it was the
eggs of males only, and, although very fruitful afterwards, she laid no
other kind.
I occupied myself the remainder of 1787, and the two subsequent years,
with experiments on retarded fecundation, and had constantly the same
results. It is undoubted, therefore, that when the copulation of queens
is retarded beyond the twentieth day, only an imperfect impregnation is
operated: instead of laying the eggs of workers and males equally, they
will lay none but those of males.
I do not aspire to the honour of explaining this singular fact. When the
course of my experiments led me to observe that some queens laid only
the eggs of drones, it was natural to investigate the proximate cause of
such a singularity; and I ascertained that it arose from retarded
fecundation. My evidence is demonstrative, for I can always prevent
queens from laying the eggs of workers, by retarding their fecundation
until the twenty-second or twenty-third day. But, what is the remote
cause of this peculiarity; or, in other words, why does the delay of
impregnation render queens incapable of laying the eggs of workers? This
is a problem on which analogy throws no light: nor in all physiology am
I acquainted with any fact that bears the smallest similarity.
The problem becomes still more difficult by reflecting on the natural
state of things, that is when fecundation has not been delayed. The
queen then lays the eggs of workers forty-six hours after copulation,
and continues for the subsequent eleven months to lay these alone: and
it is only after this period that a considerable and uninterrupted
laying of the eggs of drones commences. When, on the contrary,
impregnation is retarded after the twentieth day, the queen begins, from
the forty-sixth hour, to lay the eggs of males, and no other kind during
her whole life. As, in the natural state, she lays the eggs of workers
only, during the first eleven months, it is clear that these, and the
male eggs, are not indiscriminately mixed in the oviducts. Undoubtedly
they occupy a situation corresponding to the principles that regulate
laying: the eggs of workers are first, and those of drones behind them.
Farther, it appears that the queen can lay no male eggs until those of
workers, occupying the first place in the oviducts, are discharged. Why,
then, is this order inverted by retarded copulation? How does it happen
that all the workers eggs which the queen ought to lay, if fecundation
was in due time, now wither and disappear, yet do not, impede the
passage of the eggs of drones, which occupy only the second place in the
ovaries. Nor is this all. I have satisfied myself that a single
copulation is sufficient to impregnate the whole eggs that a queen will
lay in the course of at least two years. I have even reason to think,
that a single copulation will impregnate all the eggs that she will lay
during her whole life: but I want absolute proof for more than two
years. This, which is truly a very singular fact in itself, renders the
influence of retarded fecundation still more difficult to be accounted
for. Since a single copulation suffices, it is clear that the male fluid
acts from the first moment on all the eggs that the queen will lay in
two years. It gives them, according to your principles, that degree of
_animation_ that afterwards effects their successive expansion. Having
received the first impressions of life, they grow, they mature, so to
speak, until the day they are laid: and as the laws of laying are
constant, because the eggs of the first eleven months are always those
of workers, it is evident that those which appear first are also the
eggs that come soonest to maturity. Thus, in the natural state, the
space of eleven months is necessary for the male eggs to acquire that
degree of increment they must have attained when laid. This consequence,
which to me seems immediate, renders the problem insoluble. How can the
eggs, which should grow slowly for eleven months, suddenly acquire their
full expansion in forty-eight hours, when fecundation has been retarded
twenty-one days, and by the effect of this retardation alone? Observe, I
beseech you, that the hypothesis of successive expansion is not
gratuitous; it rests on the principles of sound philosophy. Besides, for
conviction that it is well founded, we have only to look at the figures
given by Swammerdam of the ovaries of the queen bee. There we see eggs
in that part of the oviducts contiguous to the vulva, much farther
advanced, and larger than those contained in the opposite part.
Therefore the difficulty remains in full force: it is an abyss where I
am lost.
The only known fact bearing any relation to that now described, is the
state of certain vegetable seeds, which, although extremely well
preserved, lose the faculty of germination from age. The eggs of workers
may also preserve, only for a very short time, the property of being
fecundated by the seminal fluid; and, after this period, which is about
fifteen or eighteen days, become disorganised to that degree, that they
can no longer be animated by it. I am sensible that the comparison is
very imperfect; besides, it explains nothing, nor does it even put us
on the way of making any new experiments. I shall add but one reflection
more.
Hitherto no other effect has been observed from the retarded
impregnation of animals, but that of rendering them absolutely sterile.
The first instance of a female still preserving the faculty of
engendering males, is presented by the queen bee. But as no fact in
nature is unique, it is most probable that the same peculiarity will
also be found in other animals. An extremely curious object of research
would be to consider insects in this new point of view, I say _insects_,
for I do not conceive that any thing analogous will be found in other
species of animals. The experiments now suggested would necessarily
begin with insects the most analogous to bees; as wasps, humble bees,
mason bees, all species of flies, and the like. Some experiments might
also be made on butterflies; and, perhaps, an animal might be found
whose retarded fecundation would be attended with the same effects as
that of queen bees. Should the animal be larger, dissection will be more
easily accomplished; and we may discover what happens to the eggs when
retarded fecundation prevents their expansion. At least, we might hope
that some fortunate circumstance would lead to solution of the
problem{G}.
Let us now return to my experiments. In May 1789, I took two queens just
when they had undergone the last metamorphosis: one was put in a _leaf
hive_, well provided with honey and wax, and sufficiently inhabited by
workers and males. The other was put into a hive exactly similar, from
which all the drones were removed. The entrances of these hives were
too confined for the passage of the females and drones, but the common
bees enjoyed perfect liberty. The queens were imprisoned thirty days;
and being then set at liberty, they departed, and returned impregnated.
Visiting the hives in the beginning of July, I found much brood, but
wholly consisting of the worms and nymphs of males. There actually was
not a single worker's worm or nymph. Both queens laid uninterruptedly
until autumn, and constantly the eggs of drones. Their laying ended in
the first week of November, as that of my other queens.
I was very earnest to learn what would become of them in the subsequent
spring, whether they would resume laying, or if new fecundation would be
necessary; and if they did lay, of what species the eggs would be.
However, the hives being very weak, I dreaded they might perish during
winter. Fortunately, we were able to preserve them; and from April 1790,
they recommenced laying. The precautions we had taken prevented them
from receiving any new approaches of the male. Their eggs were still
those of males.
It would have been extremely interesting to have followed the history of
these two females still farther, but, to my great regret, the workers
abandoned their hives on the fourth of May, and that same day I found
both queens dead. No weevils were in the hive, which could disturb the
bees; and the honey was still very plentiful: but as no workers had been
been produced in the course of the preceding year, and winter had
destroyed many, they were too few in spring to engage in their wonted
labours, and, from discouragement, deserted their habitation to occupy
the neighbouring hives.
In my Journal, I find a detail of many experiments on the retarded
impregnation of queen bees, so many, that transcribing the whole would
be tedious. I may repeat, however, that there was not the least
variation in the principle, and that whenever the copulation of queens
was postponed beyond the twenty-first day, the eggs of males only were
produced. Therefore, I shall limit my narrative to those experiments
that have taught me some remarkable facts.
A queen being hatched on the fourth of October 1789, we put her into a
leaf-hive. Though the season was well advanced, a considerable number of
males was still in the hive; and it here became important to learn,
whether, at this period of the year, they could equally effect
fecundation; also, in case it succeeded, whether a laying, begun in the
middle of autumn, would be interrupted or continued during winter. Thus,
we allowed the queen to leave the hive. She departed, indeed, but made
four and twenty fruitless attempts before returning with the evidence of
fecundation. Finally, on the thirty-first of October, she was more
fortunate: She departed, and returned with the most undoubted proof of
the success of her amours: She was now twenty-seven days old,
consequently fecundation had been retarded. She ought to have begun
laying within forty-six hours, but the weather was cold, and she did not
lay; which proves, as we may cursorily remark, that refrigeration of the
atmosphere is the principal agent that suspends the laying of queens
during winter. I was excessively impatient to learn whether, on the
return of spring, she would prove fertile, without a new copulation. The
means of ascertaining the fact was easy; for the entrances of the hives
only required contraction, so as to prevent her from escaping. She was
confined from the end of October until May. In the middle of March, we
visited the combs, and found a considerable number of eggs, but, none
being yet hatched, we could not know whether they would produce workers
or males. On the fourth of April, having again examined the state of the
hive, we found a prodigious quantity of nymphs and worms, all of
drones; nor had this queen laid a single worker's egg.
Here, as well as in the preceding experiment, retardation had rendered
the queens incapable of laying the eggs of workers. But this result is
the more remarkable, as the queen did not commence laying until four
months and a half after fecundation. It is not rigorously true,
therefore, that the term of forty-six hours elapses between the
copulation of the female and her laying; the interval may be much
longer, if the weather grows cold. Lastly, it follows, that although
cold will retard the laying of a queen impregnated in autumn, she will
begin to lay in spring without requiring new copulation.
It may be added, that the fecundity of the queen, whose history is given
here, was astonishing. On the first of May, we found in her hive,
besides six hundred males, already flies, two thousand four hundred and
thirty-eight cells, containing either eggs or nymphs of drones. Thus,
she had laid more than three thousand male eggs during March and April,
which is above fifty each day. Her death soon afterwards unfortunately
interrupted my observation, I intended to calculate the total number of
male eggs that she should lay throughout the year, and compare it with
those of queens whose fecundation had not been retarded. You know, Sir,
that the latter lay about two thousand male eggs in spring; and another
laying, but less considerable, commences in August, also in the
interval, that they produce the eggs of workers almost solely. But it is
otherwise with the females whose copulation has been retarded: they
produce no workers' eggs. For four or five months following, they lay
the eggs of males without interruption, and in such numbers, that, in
this short time, I suppose one queen gives birth to more drones than a
female, whose fecundation has not been retarded, produces in the course
of two years. It gives me much regret, that I have not been able to
verify this conjecture.
I should also describe the very remarkable manner in which queens, that
lay only the eggs of drones, sometimes deposit them in the cells.
Instead of being placed in the lozenges forming the bottom, they are
frequently deposited on the lower side of the cells, two lines from the
mouth. This arises from the body of such queens being shorter than that
of those whose fecundation has not been retarded. The extremity remains
slender, while the first two rings next the thorax are uncommonly swoln.
Thus, in disposing themselves for laying, the extremity cannot reach the
bottom of the cells on account of the swoln rings; consequently the eggs
must remain attached to the part that the extremity reaches. The worms
proceeding from them pass their vermicular state in the same place where
the eggs were deposited, which proves that bees are not charged with the
care of transporting the eggs as has been supposed. But here they
follow another plan. They extend beyond the surface of the comb those
cells where they observe the eggs deposited, two lines from the mouth.
Permit me, Sir, to digress a moment from the subject, to give the result
of an experiment which seems interesting. Bees, I say, are not charged
with the care of transporting into cells, the eggs misplaced by the
queen: and, judging by the single instance I have related, you will
think me well entitled to deny this feature of their industry. However,
as several authors have maintained the reverse, and even demanded our
admiration of them in conveying the eggs, I should explain clearly that
they are deceived.
I had a glass hive constructed of two stages; the higher was filled with
combs of large cells, and the lower with those of common ones. A kind of
division, or diaphraghm, separated these two stages from
each other, having at each side an opening for the passage of the
workers from one stage to the other, but too narrow for the queen. I
put a considerable number of bees into this hive; and, in the upper
part, confined a very fertile queen that had just finished her great
laying of male eggs; therefore she had only those of workers to lay, and
she was obliged to deposit them in the surrounding large cells from the
want of others. My object in this arrangement will already be
anticipated. My reasoning was simple. If the queen laid workers' eggs in
the large cells, and the bees were charged with transporting them if
misplaced, they would infallibly take advantage of the liberty allowed
to pass from either stage: they would seek the eggs deposited in the
large cells, and carry them down to the lower stage containing the cells
adapted for that species. If, on the contrary, they left the common eggs
in the large cells, I should obtain certain proof that they had not the
charge of transporting them.
The result of this experiment excited my curiosity extremely. We
observed the queen several days without intermission. During the first
twenty-four hours, she persisted in not laying a single egg in the
surrounding cells; she examined them one after another, but passed on
without insinuating her belly into one. She was restless, and traversed
the combs in all directions: her eggs appeared an oppressive burden, but
she persisted in retaining them rather than they should be deposited in
cells of unsuitable diameter. The bees, however, did not cease to pay
her homage, and treat her as a mother. I was amused to observe, when she
approached the edges of the division separating the two stages, that she
gnawed at them to enlarge the passage: the workers approached her, and
also laboured with their teeth, and made every exertion to enlarge the
entrance to her prison, but ineffectually. On the second day, the queen
could no longer retain her eggs: they escaped in spite of her, and fell
at random. Then we conceived that the bees would convey them into the
small cells of the lower stage, and we sought them there with the utmost
assiduity; but I can safely affirm there was not one. The eggs that the
queen still laid the third day disappeared as the first. We again sought
them in the small cells, but none were there. The fact is, they are ate
by the workers; and this is what has deceived the naturalists, who
supposed them carried away. They have observed the misplaced eggs
disappear, and, without farther investigation, have asserted that the
bees convey them elsewhere: they take them, indeed, not to convey them
any where, but to devour them. Thus nature has not charged bees with the
care of placing the eggs in the cells appropriated for them, but she has
inspired females themselves with sufficient instinct to know the species
of eggs they are about to lay, and to deposit them in suitable cells.
This has already been observed by M. de Reaumur, and here my
observations correspond with his. Thus it is certain that in the natural
state, when fecundation takes place at the proper time, and the queen
has suffered from nothing, she is never deceived in the choice of the
cells where her eggs are to be deposited; she never fails to lay those
of workers in small cells, and those of males in large ones. The
distinction is important, for the same certainty of instinct is no
longer conspicuous in the conduct of those females whose impregnation
has been deferred. I was oftener than once deceived respecting the eggs
that such queens laid, for they were deposited indiscriminately in small
cells and those of drones; and not aware of their instinct having
suffered, I conceived that the eggs in small cells would produce
workers; therefore I was very much surprised, when, at the moment they
should have been hatched, the bees closed up the cells, and
demonstrated, by anticipation, that the included worms would change into
drones; they actually became males; those produced in small cells were
small, those in large cells large. Thus I must warn observers, who would
repeat my experiments on queens that lay only the eggs of males, not to
be deceived by these circumstances, and expect that eggs of males will
be deposited in the workers cells.
It is a singular fact, that the females, whose fecundation has been
retarded, sometimes lay the eggs of males in royal cells. I shall prove,
in the history of swarms, that immediately when queens, in the natural
state, begin their great laying of male eggs, the workers construct
numerous royal cells. Undoubtedly, there is some secret relation between
the appearance of male eggs and the construction of these cells; for it
is a law of nature from which bees never derogate. It is not surprising,
therefore, that such cells are constructed in hives governed by queens
laying the eggs of males only. It is no longer extraordinary that these
queens deposit in the royal cells, eggs of the only species they can
lay, for in general their instinct seems affected. But what I cannot
comprehend is, why the bees take exactly the same care of the male eggs
deposited in royal cells, as of those that should become queens. They
provide them more plentifully with food, they build up the cells as if
containing a royal worm; in a word, they labour with such regularity
that we have frequently been deceived. More than once, in the firm
persuasion of finding royal nymphs, we have opened the cells after they
were sealed, yet the nymph of a drone always appeared. Here the instinct
of the workers seemed defective. In the natural state, they can
accurately distinguish the male worms from those of common bees, as they
never fail giving a particular covering to the cells containing the
former. Why then can they no longer distinguish the worms of drones when
deposited in the royal cells? The fact deserves much attention. I am
convinced that to investigate the instinct of animals, we must
carefully observe where it appears to err.
Perhaps I should have begun this letter with an abstract of the
observations of prior naturalists, on queens laying none but the eggs of
males; however, I shall here repair the omission.