§ II. THE HEAD AND ORGANS OF SENSATION.
The head of the queen ([Plate I. Fig. 1 c]), as also that of the drone ([Fig. 3 c]), is rounder than that of the worker bee. This last ([Fig. 2 c]) is of a triangular shape, and much flattened, as in [Fig. 2 c*], which shows the side view. In common with other creatures, the head contains the inlet for nutrition, and is the seat of the principal organs of sensation.
In the figures before alluded to may be seen the double visual apparatus with which bees are provided. The oval lobes on each side of the head represent the two eyes, the secondary organs of vision being the three small eyes on the top of the head, called "stemmata." We shall first describe the two larger eyes, which, as seems to be the case with all insects, are immovable, and have neither irides nor pupils, nor yet eyelids to cover them, but are protected from the dust or pollen of flowers by a number of small hairs, as well as by a horny tunicle, which defends and secures them from injury. The multitude of hexagonal lenses, called "ocelli," which make up the eye of a bee, give it, when viewed through a microscope, the appearance of honeycomb; or we might compare it to a multiplying-glass with hexahedral facets, each facet representing the surface of one ocellus. But when we look also to the inner structure, it resembles rather some thousands of telescopes all converging towards one point. It has been computed that in each eye there are 3,500 of these collateral lenses. Fig. 5 in [Plate II.] represents three of these prisms or lenses magnified. Each of them is wonderfully intricate in structure, comprising, first two plano-convex lenses of different densities, fitted together on the flat sides on the principle of an achromatic object-glass; next an empty space surrounded with dark pigment, which is convex within like the neck of a vase, so as to narrow the passage for the rays to about one-half the diameter, or one-fourth the superficial space; and lastly a longer conical lens, convex at each end and communicating with the optic nerve. The simple eyes, or stemmata, on the contrary, are as strictly simple as their name implies, consisting of one nearly globular lens apiece.
The construction of the eye for seeing objects best at a moderate distance will account for the fact that bees mount high up into the air after collecting their store of food, and then, having determined the point, no matter how far off, they fly homewards with the directness of a cannon-ball, and alight at the door of their own habitation, though the country around may be crowded with hives; but on reaching the entrance their vision appears defective, for they then feel their way with the antennæ as if totally blind, and should the hive have been moved a little they will rise again into the air to obtain a more distant view, suited to the lengthened focus of their sight. When a stock or swarm is brought from a distance the bees do not take their departure at once, but reconnoitre awhile, visiting surrounding objects so as to well know the spot again in order to return thereto.
The distinct purposes of the two different kinds of eyes may not perhaps be yet determined with certainty, but Pastor Schönfeld (whom Von Berlepsch employs to write those sections of his own work that relate to the senses of bees, as being "beyond doubt the best-informed of apiarians on these subjects") gives a decided opinion that the stemmata serve only for the most distant objects, while the compound eyes, which are much more highly refractive, become available when closer at hand. Thus these eyes, which we compared to telescopes, are credited with the least of telescopic power, and serve for nearer observation after all. How much nearer, however, we are not yet in a position to say, and nothing need be withdrawn of what is stated above as to the far-sightedness of bees. The compound eyes are assumed to be also serviceable in the twilight, and thus to afford some vision in the interior of a hive. It is worth mentioning, as a rare compliment from a German to an English apiarian, that Schönfeld declares the best anatomical description of the eyes of our insect to be given by Samuelson in his work, "The Honey Bee."[19]
[19] The compliment belongs doubtless to Dr. Hicks, to whom the anatomical portion of that work is presumably due.
The mouth of the bee is a most complex structure, marvellously adapted for its duties, and consists of the labrum, or upper lip, with the mandibles, or upper gills, and of the labium, or lower lip, which is made up of the ligula or tongue, also called the proboscis, the labial palpi, and the paraglossæ, together with the maxillæ, or lower gills—we adopt this word "gills" from the German for want of a better. The jaws open vertically, but the mandibles, maxillæ, and palpi work horizontally, and serve as pincers or scissors. The mandibles are the two side pieces which constitute the working portion of the upper jaw. [Fig. 1 d] in [Plate I.] shows the mandible of the queen, which, like that of the drone ([Fig. 3 d]), is provided with two teeth, whilst the mandible of the worker ([Fig. 2 d]) is without teeth. This last having to manipulate the wax with smoothness, the teeth would doubtless be objectionable. These mandibles are strong, horny, and sharp-pointed, to assist in breaking down food, and in other respects constitute serviceable tools for seizing their enemies, ejecting the drones, etc.
The tongue ([Plate II. Fig. 3]), or proboscis, is a long slender projection, flattish in form, and about the thickness of a bristle. It has about forty cartilaginous rings, each of which is fringed with minute hairs, having also a small tuft of hair at its extremity, where it is somewhat serrated. In movement it is like the trunk of an elephant, and is susceptible of extension and contraction, bending and twisting in all directions; and by rolling about, it sweeps or laps up, by means of the fringes around it, everything to which it is applied. Thus, when a bee alights upon a flower, it pierces the petals and stamens, where the nectar is secreted, and deposits its collection on the tongue, from whence it passes into the gullet ([Plate I. Fig. 2 c]) at its base. At times, in building combs, the tongue is used as a trowel, with which the minute scales of wax are deposited in their appropriate places, and the desired finish is given to the cells. This organ has been denied by some to be a hollow tube, but this is not the view generally held, and it certainly does not act wholly by handing up the food, for there is a furrow or gutter running along the whole length of its under side. Thus, when a bee is imbibing honey the rings of the abdomen have a vibratory motion similar to pumping, showing to the casual observer that suction is rapidly going on. Dr. Bevan tells us that the true tongue is an extremely minute object at the base of the maxillæ; but this appears to have been a mistake of his own.
The labial palpi ([Plate II. Fig. 3 o]) rise from the base of each side of this lapping instrument, and are also ciliated exteriorly. They appear to serve as feelers to the mouth. Between these and the tongue are the two small sheaths or membranes called the paraglossæ; and outside of the same are the working portions of the lower jaw, or the maxillæ ([Fig. 3 n]), which are also provided with hairs and with two feelers midway known as maxillary palpi. When the jaws close on the tongue they form a sheath or defence thereto.
With the mandibles of the upper jaw opening right and left, and the maxillæ of the lower, which serve to hold the object laboured upon, the insect prepares its work for the sweeping-up apparatus of the lower parts. Thus, when combs become mouldy, or in any way unfit receptacles for brood or honey, these tools provided by Nature serve the place of hands, and the bees are able to chop up in small pieces, and remove from their dwelling, whatever lumber of this kind may be offensive to them. They are applied also for opening the anthers of flowers. The whole of this apparatus, while perfect in action in an expanded state, can be folded or coiled together when not in use, so as to form one strong and well-protected instrument.
The antennæ ([Plate I. Figs. 1 a, 2 a, 3 a]) are most important instruments, and are planted between or below the eyes and a little below the stemmata, one on each side; they consist of a number of tubular joints, each having a separate motion, and, being thus jointed throughout their whole length, they are capable of every variety of flexure, and their extremities are exquisitely sensitive. With the antennæ these insects recognise their queen, and appear to communicate to each other their joys and sorrows. For instance, if a colony be deprived of its queen, bees may be seen rushing about the hive, and, with a nervous twinge, crossing their antennæ or violently striking them together, and conveying the intelligence of their forlorn state. The sense of touch is here most acute. Huber performed an interesting experiment which definitely proved that it was by means of these organs that they communicated with each other. Dividing a hive by a grating which kept the two portions too widely apart for the antennæ to meet, he soon had the queenless half in a state of commotion and upset; but when he allowed these feelers the means of access, though nothing else could be passed through, he saw them by hundreds making their enquiries, and receiving answers, which resulted in the whole remaining tranquil. The same observer tried the experiment of depriving two queens of their antennæ and introducing both to the same hive, when the bees did not appear to know their own from the stranger; but the moment he added a third, still in possession of these organs, they fell upon her with murderous intent. Huber further points out that a moonlight night is the best time for observing the use of the antennæ as feelers. The bees, if it is warm, circumambulate their doors, to all appearance as vigilant sentinels, with these appendages stretched right before them; and woe to the moth that comes within reach—the instant it is felt its death follows.
The sense of hearing has been denied bees by some, but against all evidence; others contend that the seat of this power is also situate in their antennæ. The sounds which bees emit, particularly at swarming time, are conclusive that they possess this faculty; the only reasons for arriving at an opposite conclusion seem to be, that they are indifferent to most sounds, even the loudest, not emitted by themselves--but even to this there is the notable exception of the fright they evince at drumming on their hives—and that no precise organ of hearing can be found. Naturalists are now more united in the opinion that the seat of hearing is here located. The antennæ are said to have also another office, viz., that they act as a barometer, by which bees know the stale of the weather and are premonished of storms; the darkening of the sky seems, however, to be frequently the cause of their trooping homeward, though they care not for the loudest thunder, so long as the sun continues to shine. In the dark recesses of the hive the feelers are exceedingly serviceable, and may truly be denominated "eyes to the blind."
Bees possess acutely the sense of smell, and, attracted by the fragrance of flowers, they may be seen winging their way a considerable distance in an undeviating course, even sometimes in the face of weather which one might have thought they would not have braved. The precise seat of this sense, however, is another doubtful point. Dr. Dönhoff ascribes this also to the antennæ, stating that if these are cut off the bees lose the faculty, but regain it after a time. Schönfeld takes this as proving the case the other way; but are we not familiar with analogies in which on the loss of some organ its function has been developed elsewhere—especially when as here the rudiments of the lost part must have remained? Schönfeld's own surmise is that the faculty resides in the surfaces of the inner respiratory organs; Dr. Hicks (the assistant author of Samuelson's "Honey Bee") places it in a number of vesicles at the roots of the wings; others again attribute it to two depressions in the lower portion of the face. But Dönhoff's reference to the antennæ has experiment, to our view, in its favour, though of course not decisively so. But whether this is correct or not, this pair of horns play an important part with the useful faculties which they combine.
With their extraordinary devotion to sweets, bees can hardly but be possessed of a strong sense of taste, though in consequence of their being detected occasionally lapping the impure liquids from stable or other fœtid drains, Huber considered it the least perfect of their senses. But it is now ascertained that bees, like most animals, are fond of salt, and they therefore resort to dunghills and stagnant marshes, from which they are doubtless able to extract saline draughts. It cannot be denied, however, that, according to our ideas, their taste is otherwise at fault; thus it sometimes happens that, where onions and leeks abound and are allowed to run to seed, bees are so anxious to complete their winter stores, that, from feeding on these plants, a disagreeable flavour is communicated to the honey (see [Chap. VI. § iii.]).