THE hinder part of the bee’s body is called the abdomen, and it is here that the stomach is situated. The abdomen is larger than either the head or the thorax, and is joined to this latter by a thin waist. Insects do not possess skeletons, at least not internal skeletons of bones, such as we have. Their skeletons are outside the body, and take the form of a hard outer layer which protects the soft inner organs. This layer, or outer skin, is made of a horny substance, called chitine (pronounced “ki-tin”), which comes from a Greek word meaning a tunic or outer dress.
Chitine is indeed a wonderful substance, and is found in all forms and shapes, having a variety of appearances. The hard black bodies of beetles are composed of it, and, wonderful to relate, of this substance the downy wings of the butterfly are made. You will remember that in the chapter on the eye of the bee we saw that the facets have a beautiful appearance; they too are made of chitine, as are the tendons, legs, hairs, membranes, and many other parts of the body.
The abdomen of the queen and of the worker is divided into six rings or belts, but the drone, having a somewhat larger body, has seven. Each ring is divided again into two parts which are known as the scelerites, which are joined one to another by delicate membranes of very fine skin. You may have noticed that the leg of a crab is jointed, and that the hard outer case of shell gives place to a fine, but tough membrane at the joints. By means of this arrangement the crab can move its leg with ease. The joints of the abdomen of the bee are arranged in a similar manner, although in this case the membranes are of course much finer and more delicate than those of the crab.
The organs inside the outer case of chitine are of most wonderful and delicate construction. You may be surprised and interested to learn that a bee has two stomachs, and these are perhaps the most important parts of the abdomen. It is not because the bee is a greedy insect that it is provided with two stomachs, but each serves a separate and useful purpose. One is called the honey-sac, and the other is the stomach proper. As a bee sips the nectar from a flower, it is passed down a tube through the thorax into the honey-sac, which acts as a kind of store-chamber. Here it is kept until the bee flies back to the hive, or until the little worker may need it for its own food. Leading from the honey-sac to the stomach is a very fine tube, and at the honey-sac end of it there is a kind of stopper, called the “stomach mouth.” Just as we can open or close our mouths at will, so can the bee open or close the stomach mouth, and so either allow honey to flow into its true stomach or keep it stored in the honey-sac. The latter is very tiny, and when quite full contains little more than a third of an ordinary drop of honey. The tube which leads from the one to the other is lined with fine hairs, all pointing in a downward direction, away from the honey-sac. When the bee sips the nectar it often happens that some of the pollen grains from the flower are taken in also. Now the bee desires to gather only the pure nectar, and so it passes the nectar from the honey-sac to the stomach by means of the tube. It then makes the honey return from the stomach to the honey-sac, but this time the hairs in the tube act as a strainer, and prevent the pollen grains from returning with the nectar. By this clever little apparatus you will see that the bee is able to strain the nectar when flying from one flower to another, or when travelling back to the hive. Besides the two stomachs, the abdomen contains certain glands to which we shall refer when we come to speak of honey.
CHAPTER XVII
THE BREATHING APPARATUS
INSECTS do not breathe by means of lungs as we do but through tiny air-holes, called “spiracles.” This name comes from the Latin spiraculum, meaning an air-hole, which in turn is derived from spirare, to breathe.
Crawling insects do not need nearly so much air as flying insects, and so their breathing apparatus is not so large. In the bee the breathing tubes spread over almost the whole body, two of the largest extending along each side of the abdomen. The rings of the abdomen slightly overlap one another, and if you watch a bee carefully you will notice that they are constantly slipping in and out, like the joints of a folding telescope which is being opened and closed. This is really the action of breathing, and the bee draws in and then drives out air. If you have ever rescued a fly which has fallen into the milk, you will remember that it at once commences to clean itself vigorously with its legs. It does not do this to make itself tidy, but to clean out the milk which clogs its air-tubes and is thus choking it.
It is interesting to notice that the mouth of each air-tube has a number of tiny hairs; these serve to keep out dust, which would interfere with the breathing. The air-tubes branch off one from another like the roots of a tree, and in order to give you some idea of how very small they are, I may tell you that it has been found that a bundle of a quarter of a million of them would hardly be any bigger than an ordinary human hair!
Plate XIII
