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Eyes, Antenne, and Brain: Butler
Whether the bee's two compound eyes focus together, as do our two eyes, is another matter, and probably they do not, as in the honey-gatherers the eyes are well over on the side of the head, and probably each one gives an image independently of the other. In Butler's " Feminin Monarchi," written in 1609, and reprinted in 1634, occurs a description of the bee's eyes too funny to omit; and modern science will look askance at it, though the ordinary reader, unscientific but observant, after looking a bee in the face, will at least sympathize with Butler's dilemma. For how could a man in 1634 expect to find a creature's eyes covering both sides of its head? Says Butler, "Her two cheeks being transparent like lanthorn, do serve, though immovable, instead of eyes; through which the species of things visible are conveyed to the common sense."
When examined by the microscope, the eye of the bee is found to be constructed on a plan somewhat resembling that of our own eyes, there being lenses, rods, and nerveends. The outer lens found in each facet of the bee's eye is biconvex, and this is fortified by another lens just back of it, which is long and cone-shaped.
The rods and nerve-endings back of these lenses are complex and difficult to understand, and it is enough to know that the facets of the compound eyes are very telescopic in action, enabling the bee by means of them to see far better at a distance than near at hand.
Its chief need of eyes is to discover flowers, and consequently its compound eyes are probably little more than highly trained blossom detectives. It appears to have but one idea when it goes abroad, and that is to find a nectarflowing flower as soon as possible. With its eyes to discover distant masses of color, and its antennæ to scent the nectar as it approaches, it is very well qualified to accomplish its wishes. But these great compound eyes after all are not much better than a pair of telescopes pointing about in search of clover heads, and, Eyes, Antennæ, and Brain when it comes to a near-at-hand object, the bee, as far as they are concerned, is very likely as blind as if it had no eyes. So these twelve or thirteen thousand facets have to be re-enforced by more eyes; and near the top of the head, between the compound eyes, are three other visual organs arranged in a triangle, each one large as compared with a facet, though small as compared with the compound eyes themselves. These three simple eyes are overhung by tufts of hairs like very shaggy eyebrows, and when one of them is discovered with a magnifying glass, it shines out like a bright bird's eye, the light often focusing upon it in a way to make it simulate the eye of higher animals.
These three eyes are not on the same plane, and it is difficult to see all of them at the same time, because of the hair that covers the top of the bee's head. This hair can easily be shaved off, however, as has been done in the illustration.
The central eye is lower than the two others, and is somewhat to the front of the face; it is directed up and out, so that while the two compound eyes are busy searching space for flowers on either side, this forward-looking eye perhaps prevents the eager worker from bumping its reckless head against obstacles close in front.
The two other eyes are over the edge, as it were, resting in slanting depressions on top of the head, and being directed upward and to the right and left respectively. The structure of the simple eyes, or ocelli, is somewhat similar to that of the facets, but is simpler, and the lenses are shaped for near vision. Though in some cases they do not seem to perform their part with remarkable success, they doubtless have their value.
A bee does little credit to these three eyes when stumbling about in search of something almost within reach. If its hive is moved only a few feet during its absence, or if it misses the alighting board and drops to the ground, it often wastes a great deal of time bustling about in what seems a very aimless manner before it finds itself again.
Between the hexagonal facets of the compound eyes, and slanting in the direction towards which the eye curves, so as not to obstruct vision, are hairs.
Why the bee should have hairs on its eyes may not be apparent until one remembers the unprotected state of those lidless organs. And also the fact that the eyes are constantly in danger of becoming dusted over by various substances as the bee dives its head into flower-cups, explores the waxen cells of its hive, and flies abroad on windy days.
Section of bee's eye.
It would not do for these eyes to be injured or obscured in any way, and the hairs that cover them are protective, and from their structure no doubt also sensory, so they form the body-guard of the eyes, keeping them from all harm.
Eyelids would be a great inconvenience to a bee ; eye-hairs serve every purpose and offer no inconvenience whatever. As to what a bee sees with its eyes, and how the objects familiar to us appear to the owner of these numerous optical organs, one is not in a position to state.
It is well known that bees distinguish colors, and Sir John Lubbock goes so far as to assure us that honey-bees prefer blue, he having discovered this by alternately alluring and deceiving them with slips of colored paper upon which were - or were not - drops of honey. He found his bees investigating the blue slips before trying other colors, and following the blue about when it was moved from place to Eyes, Antennæ, and Brain place, even when the honey had been transferred to some less attractive color.
Bee-keepers sometimes paint their hives different colors to enable the occupants to find their way home in a crowded apiary.
While bees undoubtedly distinguish colors, and may have their preferences, it is, as we have already seen, assuming too much to say that color is the chief factor in attracting them.
Certainly white clover heads blossoming in a meadow of overtopping grass are not conspicuous from their color, and yet here you will always find the bees. Here they will come from distant hives, if nearer clover pastures do not stay them.
How do they know? Do they scent the clover from afar? or do they recognize the color environment of white clover heads, the green smooth meadows, the low-growing vegetation ?
And when the fragrant load is gathered, what directs their homeward course? Do they recognize the particular house, barn, or clump of trees that overlooks their hive? Some sense they have that tells them its exact location, for, mounting high in the air, they turn in the right direction and make a "bee-line" for home.
Apparently their eyes deceive them at times and lead them to seek honey from the white expanse of glaciers and snow-clad mountain tops where travellers frequently speak of having seen them dead in large numbers.