During the summer a certain number of workers—for it is to the workers solely that this office is committed—may always be observed vibrating their wings before the entrance of their hive; and the observant apiarist will find upon examination, that a still greater number are engaged within it in the same employment. All those thus circumstanced that stand without, turn their head to the entrance; while those that stand within, turn their back to it. The station of these ventilators is upon the floor of the hive. They are usually ranged in files, that terminate at the entrance; and sometimes, but not constantly, form so many diverging rays, probably to give room for comers and goers to pass. The number of ventilators in action at the same time varies: it seldom much exceeds twenty, and is often more circumscribed. The time also that they devote to this function is longer or shorter according to circumstances: some have been observed to continue their vibrations for nearly half an hour without resting, suspending the action for not more than an instant, as it should seem to take breath. When one retires, another occupies its place; so that in a hive well peopled there is never any interruption of the sound or humming occasioned by this action; by which it may always be known whether it be going on or not.
This humming is observable not only during the heats of summer, but at all seasons of the year. It sometimes seems even more forcible in the depth of winter than when the temperature of the atmosphere is higher. An employment so constant, which always occupies a certain number of bees, must produce as constant an effect. The column of air once disturbed within, must give place to that without the hive; thus a current being established, the ventilation will be perpetual and complete.
To be convinced that such an effect is produced, approach your hand to a ventilating bee, and you will find that she causes a very perceptible motion in the air. Huber tried an experiment still more satisfactory. On a calm day, at the time when the bees had returned to their habitation—having fixed a screen before the mouth of the hive to prevent his being misled by any sudden motion of the external air—he placed within the screen little anemometers or wind-gauges, made of bits of paper, feather, or cotton, suspended by a thread to a crotch. No sooner did they enter the atmosphere of the bees than they were put in motion, being alternately attracted and repelled to and from the aperture of the hive with considerable rapidity. These attractions and repulsions were proportioned to the number of bees engaged in ventilation, and, though sometimes less perceptible, were never intirely suspended. Burnens tried a similar experiment in the winter, when the thermometer stood in the shade at 33°. Having selected a well-peopled hive, the inhabitants of which appeared full of life and sufficiently active in the interior, and luted it all around, except the aperture to the platform on which it stood, he stuck in the top a piece of iron wire which terminated in a hook, to which he fastened a hair with a small square of very thin paper at the other end; this was exactly opposite to the aperture, at the distance of about an inch from it. As soon as the apparatus was fixed, the hair with its paper pendulum began to oscillate more or less, the greatest oscillations on both sides being an inch, by admeasurement, from the perpendicular: if the paper was moved by force to a greater distance, the vibrations did not take place, and the apparatus remained at rest. He then made an opening in the top of the hive, and poured in some liquid honey: soon after there arose a hum, the movement in the interior increased, and some bees came out. The oscillations of the pendulum upon this became more frequent and intense, and extended to fifteen lines or an inch and a quarter from the perpendicular; but when the paper was removed to a greater distance from the aperture, it remained at rest.
Huber, at the proposal of M. de Saussure, in order to ascertain whether artificial ventilators would produce an analogous effect, got a mechanical friend to construct for him a little mill with eighteen sails of tin. He also prepared a large cylindrical vase, into which he could, at an aperture in the box upon which it was fixed, introduce a lighted taper. In one side of this box was another aperture to represent that of a hive, but larger. The ventilator was placed below, and luted at the points of contact, and anemometers were suspended before the aperture. The first experiment was the introduction of the taper, without putting the ventilator in motion. Though the capacity of the vessel was about 3228 cubic inches, the flame soon diminished, and went out in about eight minutes, and the anemometers continued motionless. The same experiment was next repeated with the door shut, with precisely the same result. After the air of the vessel had been renewed, the taper was again introduced, and the ventilator set in motion: immediately, as appeared by the oscillations of the anemometers, two currents of air were established, and the brilliancy of the flame was not diminished during the whole course of the experiment, which might have been prolonged for an indefinite time. A thermometer placed in the lower part of the apparatus rose to 112°; and the temperature was evidently still more elevated at the top of the receiver.
The Creator often has one end in view in the actions of animals, (and nothing more conspicuously displays the invisible hand that governs the universe,) while the agents themselves have another. This probably is the case in the present instance, since we can scarcely suppose that the bees beat the air with their wings in order to ventilate the hive, but rather to relieve themselves from some disagreeable sensation which oppresses them. The following experiments prove that one of their objects in this action, as it is with ladies when they use their fans, is to cool themselves when they suffer from too great heat. When Huber once opened the shutter of a glazed hive, so that the solar rays darted upon the combs covered with bees, a humming, the sign of ventilation, soon was heard amongst them, while those which were in the shade remained tranquil. The bees composing the clusters which often are suspended from the hives in summer, when they are incommoded by the heat of the sun, fan themselves with great energy. But if by any means a shadow is cast over any portion of the group, the ventilation ceases there, while it continues in the part which feels the heat of the sun. The same cause produces a similar effect upon humble-bees, wasps, and hornets.
Amongst the bees, however, it is remarkable that ventilation goes on even in the depth of winter, when it cannot be occasioned by excess of heat.—This therefore can only be regarded as a secondary cause of the phenomenon. From other experiments, which, having already detained you too long, I shall not here detail, it appears that penetrating and disagreeable odours produce the same effect[253]. Perhaps, though Huber does not say this, the odour produced by the congregated myriads of the hive may be amongst the principal motives that impel its inhabitants to this necessary action.
Whatever be the proximate cause, it is I trust now evident to you, that the Author of nature, having assigned to these insects a habitation into which the air cannot easily penetrate, has gifted them with the means of preventing the fatal effects which would result from corrupted air. An indirect effect of ventilation is the elevated temperature which these animals maintain, without any effort, in their hive:—but upon this I shall enlarge hereafter.
Bees are extremely neat in their persons and habitations, and remove all nuisances with great assiduity, at least as far as their powers enable them. Sometimes slugs or snails will creep into a hive, which with all their address they cannot readily expel or carry out. But here their instinct is at no loss; for they kill them, and afterwards embalm them with propolis, so as to prevent any offensive odours from incommoding them. An unhappy snail, that had travelled up the sides of a glazed hive, and which they could not come at with their stings, they fixed, a monument of their vengeance and dexterity, by laying this substance all around the mouth of its shell[254]. When they expel their excrements, they go apart that they may not defile their companions: and in winter, when prevented by extreme cold, or the injudicious practice of wholly closing the door of the hive, from going out for this purpose, their bodies sometimes become so swelled from the accumulation of feces in the intestines, that when at last able to get out they can no longer fly, so that falling to the ground in the attempt, they perish with cold, the sacrifice of personal neatness[255]. When a bee is disclosed from the pupa and has left its cell, a worker comes, and taking out its envelope carries it from the hive; another removes the exuviæ of the larva, and a third any filth or ordure that may remain, or any pieces of wax that may have fallen in when the nascent imago broke from its confinement. But they never attempt to remove the internal lining of silk that covers the walls, spun by the larva previous to its metamorphosis, because, instead of being a nuisance, it renders the cell more solid[256].
Having now described to you the usual employments of my little favourites both within doors and without, I shall next enlarge a little upon their language, memory, tempers, manners, and some other parts of their history.
"Brutes" (it is the remark of Mr. Knight) "have language to express sentiments of love, of fear, of anger; but they seem unable to transmit any impression they have received from external objects. But the language of bees is more extensive; if not a language of ideas, it is something very similar[257]." You have seen above that the organ of the language of ants is their antennæ. Huber has proved satisfactorily, that these parts have the same use with the bees. He wished to ascertain whether, when they had lost a queen (intelligence which traverses a whole hive in about an hour) they discovered the sad event by their smell, their touch, or any unknown cause. He first divided a hive by a grate, which kept the two portions about three or four lines apart; so that they could not come at each other, though scent would pass. In that part in which there was no queen, the bees were soon in great agitation; and as they did not discover her where she was confined, in a short time they began to construct royal cells, which quieted them. He next separated them by a partition through which they could pass their antennæ, but not their heads. In this case the bees all remained tranquil, neither intermitting the care of the brood, nor abandoning their other employments; nor did they begin any royal cell. The means they used to assure themselves that their queen was in their vicinity and to communicate with her, was to pass their antennæ through the openings of the grate. An infinite number of these organs might be seen at once, as it were, inquiring in all directions; and the queen was observed answering these anxious inquiries of her subjects in the most marked manner; for she was always fastened by her feet to the grate, crossing her antennæ with those of the inquirers. Various other experiments, which are too long to relate, prove the importance of these organs as the instrument of communicating with each other, as well as to direct the bee in all its proceedings[258]. Besides their antennæ, the bees also cause themselves to be understood by certain sounds, not indeed produced by the mouth, but by other parts of their body:—but upon this subject I shall have occasion to enlarge hereafter.