The antenna are certainly touch-organs, and, in all likelihood, it is by their means that the bee hears and smells. Yet this only exhausts a few of their manifest possibilities. It is quite clear that we must admit the honey-bee to possess other senses than the five we know of; and—for a guess—some of these mysterious implements on her antenna may be thought-transmitters and -receivers on the wireless plan. The wonderful unanimity of action among bees may be due to the fact that they can exchange ideas through the air, as men have now at last come to do. The faculty of speech, hitherto held up as man’s insignia of lordship over the rest of creation, may be indeed a crude, archaic thing, compared with the mind-language of the honey-bees.
There is another conceivable function which the antennæ of bees may perform—that of unerring and instant estimation of short distances. They may be delicate measuring instruments, not mechanically applied in the way of a foot-rule or metric scale, but registering dimensions inherently, as our ears record intensity of sound. This would go far to explain how honeycomb is built, how the cells are made all of the same shape and size, although hundreds of the mason-bees are at work on the structure, not only at the same moment, but in succession, each bee coming and going in the murmurous gloom of the hive, and beginning instantly and unhesitatingly at the point where her predecessor broke off. As the central division of the comb grew, expanding in all directions downward, and the cells were built out horizontally at the same time, the bee would know by her sense of dimension when the limit of each side in the hexagonal cell-base was reached, and would know the proper angle to turn off at in the laying of the next foundation-line.
Anyone who has watched the flight of the bee must have been struck by its sheer facility and freedom no less than by its speed. It is quite evident that the bee is not only an accomplished aërial navigator, but that she sustains and propels herself through the air with very little effort. Obviously her equipment for flight must be a thoroughly efficient one, and yet at first glance it is not quite clear how she manages so well. The student of the flight-problem, taking his ideas and conception of first principles from the flight of birds, is accustomed to believe that there are at least two vital indispensable elements in the process—a pair of wings or combination of aëroplane and propellers that will sustain as well as drive, and some sort of steering-apparatus like the bird’s tail. Yet, as far as a first general inspection carries us, the bee appears to have no rudder-mechanism at all, but to depend on her four wings for every purpose. The wings of the bird have a variable action. They can be used together or separately, and are as capable of eccentric adjustment, both in themselves and in relation to one another, as a pair of human arms. But the bee’s wings have none of this adaptability. They have but the one motion, up and down; and they work symmetrically, each wing keeping time with its fellow. Yet the bee steers herself perfectly well in a hundred different evolutions, accomplishing all that the bird attains with his more complicated apparatus for flight.
The whole problem is bound up with another problem; and the two, difficult of solution apart, easily resolve one another when taken in conjunction. Insects are so called because their bodies are in two parts, entirely divided except for an extremely slender connecting joint. We are so accustomed to accept this arrangement as a common fact in nature that we seldom stop to consider its real significance. It is not easy to see how such a construction can be anything else than a drawback to any living creature. But in the hive-bee the whole arrangement seems to amount to what must be called an ideal inconvenience, seeing that her honey-sac and complicated organs for producing the larval food are in her abdomen, with no way to them but through this fine joint. Clearly there is some weighty reason for it, out-balancing all other considerations, or it would not exist; and when we come to study it in connection with the honey-bee’s peculiar system of flight, we soon arrive at the true solution.
It has been said that the wings of the bee have a perfectly symmetrical action, and that they have a single fixed direction, moving up and down, always at right-angles with the line of the thorax. Under the microscope each of the four wings is seen as a transparent, impervious membrane, intersected with fine ribs. The front wing, however, has a much stronger and stiffer rib running the entire length of its upper edge, and it is on this main rib that almost the entire force of the flight-muscles is concentrated. If you look farther, you will see that the under wing has a row of fine hooks along its top edge, while the lower edge of the upper wing is flanged or folded back. In flight the hooks on one wing engage with the flange on the other, and thus the wings on each side are automatically locked together, forming one continuous air-resisting surface. This combined wing is very flexible throughout, except at its upper edge, where it is stiffened by the main rib. In action, therefore,—the force being applied practically to the edge alone, which resists the air while the rest of the wing bends to it—the result is that the whole wing becomes an oscillating, inclined plane, whose inclination, forward on the down-stroke, is still forward on the up-stroke, because the plane-inclination reverses itself automatically.
From this it will be understood how the flexible wings of the bee are used in straightforward flight; but, seeing that the wings themselves are incapable of independent or irregular action, it is not yet clear how the bee contrives to steer herself, rising or descending, or turning sideways, just as the mood seizes her. It is here that the reason for the peculiar construction of her body becomes plain. The fine link which unites her abdomen to her thorax is really an universal joint, actuated by a series of powerful cross-muscles, and the bee steers herself through the air by using the weight of the lower half of her body as a counterpoise. By swinging her heavy abdomen forward or backward, or from side to side, she changes her centre of gravity, and the line of force of her aëroplanes, at one and the same time. Actually her body keeps its vertical position, being her heaviest part, and it is the lighter wing-supporting thorax which is deflected. But the result is the same, and every variety and direction of flight is accomplished by the bee on what seems a far more simple plan than that evidenced in the flight of birds.
One of the most difficult things to account for in the life of the honey-bee is the fact that the temperature of the hive can be varied at the will of its occupants. The system of mechanical ventilation will, of course, explain how the hive is kept cool in the greatest heats of summer, but it does not explain the sudden accessions of heat to which it is liable from time to time. These occur principally when the wax is being generated. Under the bronze armour-plates of her body the worker-bee has six shallow, but broad depressions, beneath which the wax-glands are placed. Perfect rest and a high temperature seem to be necessary for the stimulation of these glands, and the wax-makers consume a large quantity of sweet-food during the process. It is generally stated that bees fill themselves from the stores of mature honey before uniting in the cluster; but it is more probable that the food consumed during wax-making is principally the nectar, almost as gathered from the flowers. This view is confirmed by certain experiments which were undertaken to decide the amount of food assimilated during the production of a given weight of wax. When the bees had access only to honey, it was found that five or six pounds were needed during the time that one pound of wax was produced. But if the bees were fed on a plain syrup of cane-sugar, more wax was generated. The chemical composition of fresh nectar is almost identical with that of sugar from the sugar-cane, but mature honey contains practically no cane-sugar at all. It is very doubtful, therefore, if the economic bee would deplete her hard-won stores of honey for a purpose that could be better accomplished in another and cheaper way. And it should also be borne in mind that the natural time for comb-building coincides with the season when nectar is in greatest plenty.
These sudden variations in temperature appear to be brought about by a wholesale increase in the rate of respiration among the bees; and there is nothing that excites the wonder of the student of hive-life more than the breathing-apparatus of the bee, as seen under the microscope. Practically her whole physical system is directly supplied with air, drawn in through her many spiracles. As far as scientists have been able to determine, there is not a fibre or nerve in her entire body that is not reached by the minute ramifications of the air-ducts, in direct communication with the great main breathing-vessels in the bee’s abdomen. Respiration appears to be largely voluntary with the honey-bee. She breathes only when the necessity for it arises, and will sometimes arrest the action entirely for three or four minutes together. But when the wax-making is going forward, or swarming-time is near at hand, the quick, vibratory movement of respiration is visible everywhere in the throng of bees, and the temperature of the hive climbs up often to a dozen degrees above its normal point.
The breathing system of the honey-bee is closely connected with her sound-organs. Anyone asked to describe the note made by a bee would probably say that she hums or buzzes, and there would be an end to most ideas on the matter. But to the beeman this is a pitifully inadequate statement of the truth. The bee comprises in herself not one, but a whole choir of voices, and she has a compass of at least an octave and a half. Every one of her fourteen spiracles, and each of her wings, is capable of producing sound; and these sounds can be endlessly varied in quality, intensity, and pitch. It is no exaggeration to say that the honey-bee is as accomplished a musician as any bird; but as each individual voice is for the most part lost in the general symphony of the hive, it is difficult to get a complete idea of her capabilities as a soloist.
The voice-apparatus in the spiracles is one of the most intricate things in the whole anatomy of the bee. It has a multiplicity of parts, and is obviously designed to convey a great variety of sounds. The wings also produce tones that run up or down in the scale, according to their rate of oscillation; and from them comes the sibilant note usually called buzzing. Listening to the hive-music at any season of the year, it is impossible to resist the thought that bees not only hold individual communication by means of these infinitely varied sounds, but that the general note given out by the multitude unerringly expresses the state of affairs within the hive for the time being. A prosperous stock voices its busy contentment in a way impossible to misunderstand. It is a deep, blithe, resonant sound, like the steady running of well-oiled machinery, each wheel adding its own whirring melody to the general theme. Weak or famishing colonies give out a wavering, intermittent note, the very voice of complaint and fear for the future. When a hive has lost its queen, a capable bee-master should have no difficulty in divining the trouble by listening at the hive-entrance. A queenless stock is all clamour and the hubbub of divided counsels. The ordinary rich reverberation of labour stops, and a sound of panic goes to and fro in the hive unceasingly. If a hive be quietly opened, and its queen removed with little disturbance, it may be some time before the bees discover their loss. Some colonies experimented with in this way realise their deprivation immediately, and the hue-and-cry begins at once. But one of the most curious facts in bee-life is the variation in intelligence, and alertness of perception, between the different hives. A steady-going, dull race may be a considerable time before it perceives the absence of its queen. The common note of work goes on unchanged until the fact dawns on it. And then the peculiar shrill outcry commences, overpowering all other sounds until reason again asserts itself in the colony, and the bees set about the work of raising another queen.