THE EYES
The same tiny head, which carries the marvelous antennæ, is provided
with two large “compound” eyes, as they are called. If you are able to
examine these eyes with a magnifying glass, you will at once see that
they are lovely objects. The eye itself is of a deep purplish-black
colour, and has an appearance which is rather difficult to describe.
It seems almost as though it is covered with the finest satin, for it
glistens in the sunlight.
The microscope shows that this appearance is due to the eye being
composed of multitudes of six-sided cells, resembling, in fact, nothing
so much as a piece of honeycomb. These cells are called _facets_,
which means “little faces,” and each one measures about 1/1000th part
of an inch in diameter. Over the surface of the eye are distributed
numerous long, straight hairs; the chief purpose of these hairs is to
protect the delicate facets, just as the eyelashes of our own eyes
protect them. Bees have no eyelids, as we have, and so they have to
rely upon these hairs to protect their eyes from dust and other such
foreign bodies. The construction of the eye itself is wonderful to a
degree, but it is also very difficult to understand, because it is so
complicated and minute.
Each eye consists of a great number of facets, which are really smaller
eyes, and this is the reason the eye is called compound. The eye of the
worker contains over 6000 of them, and each one points in a slightly
different direction. Large as this number may appear, it is less than
half that possessed by the drone, whose facets actually number 13,000
in each eye. As a matter of interest, I may tell you that the queen
bee has the least number of all, having but 5000. Each facet acts as a
tiny lens. A lens, as you perhaps know, is something so shaped as to
throw an image of the object to which it is directed. A camera has a
lens of glass, and by the aid of this lens a picture can be taken of
any object to which the camera is pointed. In that case the image of
the object is thrown upon what is called a photographic plate. Our own
eyes act as lenses, and throw an image of whatever we look at, not upon
a photographic plate, but upon a sensitive surface called the _retina_.
This word comes from the Latin, and means a “small net,” and it is a
very good name, for the retina catches the picture from the pupil of
the eye, and passes it on to the brain.
Although we might imagine that these compound eyes were sufficient for
any purpose, yet we find that the bee has three more eyes; these are
called the “simple” eyes. They are situated on the top of the head, and
you may see one of them in (_b_) Plate VI. The other two are over the
top of the head, for the three eyes are arranged in this manner ∵ so
as to form a triangle. You will remember that the drone is furnished
with a far greater number of facets than the worker. Consequently the
compound eyes of the drone are much larger, and they not only take
up the whole of the space at the sides of the head, but also extend
right over the top, covering the position occupied by the simple eyes
in the worker. Owing to this fact, the drone’s simple eyes are placed
lower down, on the front of his head, their position corresponding
pretty closely to the place our own eyes occupy. The simple eyes are so
called because they do not seem to be nearly so complicated in their
construction as the compound eyes, but the microscope shows that they
also have an elaborate structure. If we were to cut open the front of a
bee’s head, we should find that the simple eyes are set like this:--
[Illustration]
You will notice that the two top ones (marked L. E. left eye and R. E.
right eye) point in an outward direction, and it is by their aid that
the bee can see sideways. The lower eye (F. E. front eye) is directed
forwards, and with it things in front can be seen. The simple eyes are
surrounded with tufts of hair (marked e. b. eyebrows), which are so
placed that they do not interfere with the range of vision.
I must just tell you something of the uses of the five eyes. At one
time it was supposed that _each_ facet of the compound eyes made a
separate image of the object to which it was directed. But this is very
improbable, for what possible use could there be in the insect seeing,
instead of the one flower at which it was looking, several thousands
of flowers each exactly like the other? It is much more likely that
every facet forms a picture of only that part of the object which is
exactly in front of it, all the pictures combining to form a single
image. No doubt the compound eyes are used for seeing things at a
distance, and the simple eyes for objects near at hand.
It has been proved that bees can distinguish between colours, and even
that they prefer certain colours to others; one of their favourite
colours is pale blue. An experiment, which is both interesting and
instructive, has often been performed, and it shows us that not only
is the bee able to tell one colour from another, but also that it
possesses a memory. Pieces of blue, yellow, and red paper are obtained,
and upon each is placed a slip of glass. A little honey is placed upon
the slip of glass which is over the blue paper, and all three are put
near a hive. A bee is caught and placed on the honey. After sucking
some of it she flies to the hive to store her treasure and quickly
returns for more. She is allowed to make several journeys between the
honey and the hive, so as to impress upon her memory that the honey is
to be found on the blue paper. Then while she is away at the hive, the
slip of glass is placed upon the yellow paper. She returns, as before,
to the blue paper, and seems puzzled at not finding the honey there,
but after a careful search, she discovers the honey on the yellow
paper. The fact that the bee came back to the blue paper proves that
she has a memory and that she is able to distinguish one colour from
another.