New observations on the natural history of bees Part 2

SIR,

All the experiments, related in my preceding letter, were made in 1787 and 1788. They seem to establish two facts, which had previously been the subject of vague conjecture: 1. The queen bee is not impregnated of herself, but is fecundated by copulation with the male. 2. Copulation is accomplished without the hive, and in the air.

The latter appeared so extraordinary, that notwithstanding all the evidence obtained of it, we eagerly desired to take the queen in the fact; but, as she always rises to a great height, we never could see what pa.s.sed. On that account you advised us to cut part off the wings of virgin queens. We endeavoured to benefit by your advice, in every possible manner; but to our great regret, when the wings lost much, the bees could no longer fly; and, by cutting off only an inconsiderable portion, we did not diminish the rapidity of their flight. Probably there is a medium, but we were unable to attain it. On your suggestion, we tried to render their vision less acute, by covering the eyes with an opaque varnish, which was an experiment equally fruitless.

We likewise attempted artificial fecundation, and took every possible precaution to insure success. Yet the result was always unsatisfactory.

Several queens were the victims of our curiosity; and those surviving remained sterile. Though these different experiments were unsuccessful, it was proved that queens leave their hives to seek the males, and that they return with undoubted evidence of fecundation. Satisfied with this, we could only trust to time or accident for decisive proof of an actual copulation. We were far from suspecting a most singular discovery, which we made in July this year, and which affords complete demonstration of the supposed event, namely, that the s.e.xual organs of the male remain with the female.{F}

FOOTNOTES:

{F} The remainder of this Chapter chiefly consists of anatomical details. These may rather be considered an interruption of the narrative; and the Translator has judged it expedient to transfer them to an Appendix.

LETTER III.

_THE SAME SUBJECT CONTINUED.--OBSERVATIONS ON r.e.t.a.r.dING THE FECUNDATION OF QUEENS._

In my first letter, I remarked, that when queens were prevented from receiving the approaches of the male until the twenty-fifth or thirtieth day of their existence, the result presented very interesting peculiarities. My experiments at that time were not sufficiently numerous; but they have since been so often repeated, and the result so uniform, that I no longer hesitate to announce, as a certain discovery, the singularities which r.e.t.a.r.ded fecundation, produces on the ovaries of the queen. If she receives the male during the first fifteen days of her life, she remains capable of laying both the eggs of workers and of drones; but should fecundation be r.e.t.a.r.ded until the twenty-second day, her ovaries are vitiated in such a manner that she becomes unfit for laying the eggs of workers, and will produce only those of drones.

In June 1787, being occupied in researches relative to the formation of swarms, I had occasion, for the first time, to observe a queen that laid none but the eggs of males. When a hive is ready to swarm, I had before observed, that the moment of swarming is always preceded by a very lively agitation, which first affects the queen, is then communicated to the workers, and excites such a tumult among them, that they abandon their labours, and rush in disorder to the outlets of the hive. I then knew very well the cause of the queen's agitation, and it is described in the history of swarms, but I was ignorant how the delirium communicated to the workers; and this difficulty interrupted my researches. I therefore thought of investigating, by direct experiments, whether at all times, when the queen was greatly agitated, even not in the time of the hive swarming, her agitation would in like manner be communicated to the workers. The moment a queen was hatched, I confined her to the hive by contracting the entrances. When a.s.sailed by the imperious desire of union with the males, I could not doubt that she would make great exertions to escape, and that the impossibility of it would produce a kind of delirium. I had the patience to observe this queen thirty-four days. Every morning about eleven o'clock, when the weather was fine and the sunshine invited the males to leave their hives, I saw her impetuously traverse every corner of her habitation, seeking to escape. Her fruitless efforts threw her into an uncommon agitation, the symptoms of which I shall elsewhere describe, and all the common bees were affected by it. As she never was out all this time, she could not be impregnated. At length, on the thirty-sixth day, I set her at liberty. She soon took advantage of it; and was not long of returning with the most evident marks of fecundation.

Satisfied with the particular object of this experiment, I was far from any hopes that it would lead to the knowledge of another very remarkable fact; how great was my astonishment, therefore, on finding that this female, which, as usual, began to lay forty-six hours after copulation, laid the eggs of drones, but none of workers, and that she continued ever afterwards to lay those of drones only.

At first, I exhausted myself with conjectures on this singular fact; the more I reflected on it, the more did it seem inexplicable. At length, by attentively meditating on the circ.u.mstances 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 r.e.t.a.r.ded. 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 r.e.t.a.r.ded fecundation.

Investigating this was no easy matter. To discover whether captivity, and not r.e.t.a.r.ded 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 r.e.t.a.r.d the copulation of a queen without keeping her in confinement. I was long embarra.s.sed 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 pa.s.sage to the workers. I also made another opening for the queen, and adapted a gla.s.s tube to it, communicating with a cubical gla.s.s 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 s.p.a.ce 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 r.e.t.a.r.ding 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 gla.s.s 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 r.e.t.a.r.ded 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 r.e.t.a.r.ded fecundation, and had constantly the same results. It is undoubted, therefore, that when the copulation of queens is r.e.t.a.r.ded 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 r.e.t.a.r.ded fecundation. My evidence is demonstrative, for I can always prevent queens from laying the eggs of workers, by r.e.t.a.r.ding 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 a.n.a.logy 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 r.e.t.a.r.ded 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 r.e.t.a.r.ded 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 pa.s.sage 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 r.e.t.a.r.ded 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 s.p.a.ce 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 r.e.t.a.r.ded twenty-one days, and by the effect of this r.e.t.a.r.dation 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 v.u.l.v.a, 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 r.e.t.a.r.ded 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 a.n.a.logous will be found in other species of animals. The experiments now suggested would necessarily begin with insects the most a.n.a.logous to bees; as wasps, humble bees, mason bees, all species of flies, and the like. Some experiments might also be made on b.u.t.terflies; and, perhaps, an animal might be found whose r.e.t.a.r.ded 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 r.e.t.a.r.ded fecundation prevents their expansion. At least, we might hope that some fortunate circ.u.mstance 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 pa.s.sage 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 r.e.t.a.r.ded 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 r.e.t.a.r.ded. 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 princ.i.p.al 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 quant.i.ty 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, r.e.t.a.r.dation 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 r.e.t.a.r.d 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 r.e.t.a.r.ded. 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 r.e.t.a.r.ded: 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 r.e.t.a.r.ded, 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 r.e.t.a.r.ded. 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 pa.s.s 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 ent.i.tled 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 gla.s.s 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 pa.s.sage 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 antic.i.p.ated. 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 pa.s.s 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 pa.s.sed 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 pa.s.sage: 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 a.s.siduity; 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 a.s.serted 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 antic.i.p.ation, 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 circ.u.mstances, 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 r.e.t.a.r.ded, 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.

In a work, _Histoire de la Reine des Abeilles_, translated from the German by _Bla.s.siere_, 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 circ.u.mstance to some unknown vice in the ovaries of the queen; but he was far from suspecting that r.e.t.a.r.ded 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 subst.i.tuting one for her whose ovaries were not impaired. But to make the subst.i.tution 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 circ.u.mstance, 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 ma.s.sacred 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 r.e.t.a.r.ded impregnation. In general it has appeared that while the queen lays male eggs, bees do not ma.s.sacre 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._