Figure 1. Bee, external anatomy.
Figure 2. Bee, internal anatomy.
Figure 3. The bees in a hive are of three kinds: (1) the queen, (2) the male drone, and (3) the female worker. Pollen is the stuff of life to all of them; it is gathered by the worker in "baskets" on each hind leg (4).
Figure 4. The pollen-basket and brush are situated on the third and hindmost pair of legs of the bee. The pollen-basket is attached to the tibia, and, as its name indicates, it is the receptacle in which the bee stores the pollen it collects. The brush is situated on the next segment below the tibia and consists of numerous rows of hairs pointing downwards. The bee gathers pollen.
Figure 5. The bee's sucking apparatus consists of a long tongue or ligula, shaped like an open gutter the edges of which can join together to form a tube. On the end of the tongue there is a tuft of hair that acts like a sponge and absorbs the liquids on which the bee feeds; a bee can only take liquid food such as nectar from flowers.
Figure 6. A bee's compound eyes, ocelli, and antennae.
Figure 7. Bees have two pairs of wings, the hind ones smaller than the front. The front margin of the hind wings carries a series of minute hooks, by means of which the fore and hind wings are coupled in flight so that they act as a single wing. This increases the efficiency of the insect's flight. (1) The wings separated. (2) The wings locked together.
Figure 8. A bee in the process of producing wax. Eight little scales of wax are seen coming out of the insect's abdomen, and they are produced by glands placed between the abdominal segments. The wax is plucked off its body by the bee and molded in its jaws, and then used to build the symmetrical cells of the honeycomb.
Figure 9. Section through a beehive.
Figure 10. How bees build their comb.
A bee is a member of the superfamily Apoidea of insects. Bees convert nectar and pollen into honey for use as food. There are about 20,000 species. Bees and flowering plants (angiosperms) are largely interdependent; plants are pollinated (or fertilized) as the bees gather their pollen. Many farmers keep bees specially for this purpose.
Most bees are solitary and each female builds her own nest, although many bees may occupy a single site. Eggs are laid in cells provided with enough pollen-nectar paste to feed the larva until it becomes a flying, adult bee. Social bees (honey bees and bumblebees), which are the main subject of this article, live in a complex society of 10,000–50,000 members. Headed by the queen, whose function is to lay eggs (up to 2,000 a day), the community comprises female workers which collect pollen and build cells, and male bees, or drones, which fertilize the few young queens that appear each fall (see Figure 3). Parasitic bees, not equipped to build hives, develop in the cells of the host working bees.
The social organisation of bees
The hive is the bees' home. In summer its population never falls below 50,000. If it were to do so the community would fail to maintain itself because there would be insufficient worker bees to provide food for the huge number of larvae that hatch from eggs laid by the queen. In every hive there is one queen, a certain number of males or drones, and numerous workers, which form the great majority of the population.
The queen is the only bee able to lay eggs. She lays them at a rate of 3,000–5,000 a day from March to September, and she may live for three or four years. The drones are the male bees. Even in the most numerous communities they rarely exceed a thousand in number. They make no contribution to the work of the hive, but in spite of this the worker bees keep them and feed them throughout the summer; but when winter comes and food becomes scarce the workers kill them all.
The workers are female bees and differ from the queen in being unable to lay eggs. They form the great majority of the community, and it is they who gather pollen and nectar and produce honey and wax to make the combs.
In winter, when there is little work to be done and only food for the bees to eat, the number of workers falls as low as 10,000, but in summer, when food and work are plentiful, it increases to 80,000 or 100,000. The worker has a far shorter life than the queen; those that survive the winter may live five or six months, but in summer the workers die after about five weeks, worn out with work.
The comb is a system of cells which the worker bees construct to contain the eggs laid by the queen and to hold the stored honey; it is made entirely of wax. It is the work of the young bees to start building it, and do this from the top, fixing the first flakes of wax to the ceiling of the hive (see Figure 8). In this way they ensure that the structure will be vertical. First one bee takes a flake of wax from its own body with its hind legs, puts it in its mouth, kneads it to a paste and sticks it to the ceiling; another does the same, placing its little pellet of wax beside that of its companion; a third follows, and so the comb is built up by the work of thousands of bees. The marvel is that the structure, built by so many workers, each of whom simply comes and places her tiny brick in position and departs, can conform to an accurate geometrical plan, which combines economy and efficiency to perfection. Mathematicians have shown that, with a given quantity of wax, no structure could be made stronger and afford more space for hatching eggs and storing honey than the comb that the bees built.
Indeed a French Entomologist, Antoine Ferchault, expressed this as a mathematical problem, the celebrated 'problem of the bees'. It states: "a cell of regular hexagonal cross-section is closed by three equal and equally inclined rhombs: calculate the smaller angle of the rhombs when the total surface area of the cell is the least possible".
|Figure 10. Honeycomb cell shape
Three leading mathematicians, a German, a Swiss, and an Englishman applied themselves to the solution, and arrived at the same result: 70° 32'. And this is exactly the angle to which the bees construct their cells.
It sometimes happens that bees begin building combs at more than one position on the ceiling of the hive. As work progresses the two or three separate combs approach each other and finally join and are fused together. In such cases the cells along the line of fusion are the same size as the rest and as perfectly hexagonal. This indicates that the bees do not begin their work at random, but at calculated distances apart, planning from the start how and where the combs will meet.
Cleaning and repairs
The job of cleaning is attended to by the young bees. They collect the dirt with their feet and jaws and throw it outside. If a foreign insect gets into the hive and is killed, and the bees then find they cannot carry or drag the body away, they embalm it is that it will not be an offence in their house when it decomposes. To do this the bees cover and seal up the body with a kind of resin collected from the sticky buds of trees, called propolis. This substance has been used from early times by man as a medicine, and it has recently been shown that it does, indeed, act as an antibiotic, stopping the growth of disease germs. The bees also use propolis as a cement to seal up holes in the hive and so keep out the cold and damp.
|Figure 11. Ventilator bees at work
When the sun gets very hot and threatens to melt the wax of the combs and harm the larvae, 'ventilator bees' station themselves at the entrance and on the inner walls and buzz their wings, creating a cooling current of air. This work is also undertaken by the bees when the air inside the hive becomes to humid. The chief importance of this is to evaporate water from the nectar when it is being turned into honey.
Often in the spring the number of newly hatched bees in a hive increases so rapidly that it becomes overcrowded, with a population three or four times as large as it can comfortably contain. If there is a new queen among the young bees, a swarm is formed. In this event the old queen voluntarily quits her home, accompanied by a great crowd of workers, which may consist of nearly half the population of the hive, which is of many thousands. The swarm flies a short distance and then the queen settles on a branch and the workers cluster round her, a living mass of bees.
Under natural conditions the swarm may remain on the branch for several days, while 'explorer bees' search the neighborhood for a suitable place for a new nest. Usually, however, the swarm is taken by a beekeeper, who provides them with a hive as their new home.
For their subsistence the bees need supplies of three kinds: pollen, nectar, and water. Pollen is the food required by the bee in the early days of its life, when it is a larva. When a bee collects pollen it never mixes different kinds in the "pollen-baskets" on its legs; until these are full the bee continues to visit the same species of flower. This is a fact of great importance from the point of view of the flowers, as it leads to correct pollination, for which the flowers depend on the bees. The pollen that has been collected is taken over by young bees who store it in cells near to those occupied by larvae, ready for distribution.
Nectar provides food for the adult bees and transformed into honey, serves as a reserve for them. It is carried to the hive by the bee in its crop or honey-stomach, where the chemical transformation to honey begins to take place. When it reaches the hive the bee passes the nectar over to the young bees, who take it into their crops and then continue the conversions to honey by evaporating water from it; nectar contains 60 per cent of water, honey only 20 per cent. Finally they store the honey in cells, which are carefully sealed.
In one flight a bee carries, on average, 50 milligrams of nectar. So it must go out 20,000 times to collect a kilogramme, or rather over 9,000 times for a pound. If we take the length of a flight as 1½ miles (i.e. three miles there and back) we get a distance of about 27,000 miles flown for every pound of nectar. A good hive, in the period of maximum bloom, will collect over twenty pounds in a day.
Water, too, is needed in the hive, especially for preparing the pollen paste for the larvae. The water is collected by the workers and brought back to their crops.
The foraging workers, divided into groups, are entirely occupied by the quest for supplies; the young bees, working inside, inform them from time to time whether the need is for pollen or nectar or water.
The language of the bees
Bees can communicate among themselves and tell each other about places where food is to be found or give warning of imminent danger. Their 'language' is expressed by figures outlined in flight or by a short dance (see Figure 12). If the bee repeatedly dances on the comb following the course indicated by the arrows, it means that it has found food in the direction of the sun. Here the 'figure' of the dance is the same but is made in the opposite direction: meaning that food is to be found in the direction away from the sun. The inclination of the straight part of the dance to an imaginary vertical line informs the others of the angle between a line to the flower and a line drawn from the sun to the hive.
|Figure 12. Dance of the bee.
The queen bee
The queen is distinguished from the other bees by the greater size of her abdomen. She lays her eggs not act at random, but by starting at the center of the comb and moving methodically in concentric circles, laying an egg in each cell. By doing this she wastes no time in searching for empty cells, and makes sure that each cell receives only one egg.
The worker bees, which surround her, are her servants; they assist her, feed her and keep her clean.
Both queen and workers come from the same larval stock. The sexual development of the few grubs chosen to replace the queen depends on their being fed a 'royal jelly' produced by special glands of the worker nursemaids.
Anatomy of the bee
See Figures 1 and 2.
Like all insects the bee has three pairs of legs. With the first pair it continually brushes and cleans its antennae, whose extraordinary sensitivity would be impaired by the slightest speck of dirt. The second pair of legs is used almost entirely as a means of support. The pollen-basket and brush are on the third pair of legs (see Figure 4).
Crop or honey-stomach
The nectar collected by the bee from the flowers she visits is stored in her crop and carried back to the hive. In the crop, chemical changes take place and the nectar is converted to honey. In the hive the honey is regurgitated and stored in the cells of the honeycomb.
These glands secrete a liquid which the worker bee regurgitates from its mouth to feed the larvae. Larvae that are destined to become queen bees receive an extra large quantity of it.
The bee, like other insects, does not breathe through its mouth, but through small openings situated along each side of the abdomen and thorax, called spiracles.
Dorsal blood vessel
The blood of the bee is a colorless liquid. The center of a bee's circulation is the dorsal vessel, a tubular sac which pulsates and so circulates the blood.
Ligula or tongue
The tongue of a bee is shaped like a trough and has a hairy pad at its tip, with which the bee sucks up liquids (see Figure 5).
The abdomen contains the digestive organs and those of reproduction, respiration, and circulation. These connect with tubes called tracheae, which conduct the air to all parts of the body, and into a kind of air sac which functions as a lung.
Mandibles (jaws) and maxillae (accessory jaws)
These are used for chewing; for kneading the wax out of which the honeycomb is made; for opening the anthers of flowers; for cleaning out the hive; and for disabling enemies.
The antennae are important sense organs which are used by the bee to touch, measure, and smell.
The oceli are three small eyes located on the top of the bee's head and arranged in a triangle. They serve for vision at close quarters and in near darkness (see Figure 6).
There is a pair of compound eyes, situated one on each side of the head. They give a panoramic view of faraway objects, magnified 60 times.
With its sting the bee injects a poisonous substance into the body of its enemy. It is used as a defense and is not normally dangerous to man. When it stings a person the bee often leaves the sting behind and so dies.
The life of a worker bee
Eggs are first laid by the queen bee. To hatch, the eggs need to be kept at a temperature of 73°–77°F. This temperature is maintained by the warmth of the bodies of young bees and of drones, or male bees, which constantly walk up and down the combs.
Three days after an egg is laid a larva hatches out of it. The larva is white without wings or legs.
The larva is fed with a very nourishing substance provided by the worker bees. It grows so quickly that in half a day it doubles its weight. The food consists of a kind of milk secreted by the pharyngeal gland of the worker bees.
The food becomes coarser after the third day and consists of a mixture of nectar and pollen, half digested by young worker bees before being fed to the larvae. On the ninth day the larva turns into a pupa and the cell in which it is lying is covered with an operculum or lid of porous wax.
Twenty-one days after the egg is laid the pupa develops into a fully formed bee complete with legs and wings. It emerges from the cell and soon begins to work.
For the first nine days of its life a bee stays at home and works inside the hive. For three days it cleans out the cells in preparation for the queen to lay eggs in them. During the next three days it feeds the older larvae with a mixture of pollen and nectar, and for the last three days it feeds the younger larvae with the substance secreted by its pharyngeal glands.
Between the tenth and twentieth days of its life a bee performs mixed duties. It stores in special cells the pollen brought by other bees to the hive; it builds the honeycombs, for it is during this period that the bee produces wax from glands in its abdomen; it makes its first trial or orientation flights; and it stands guard at the door of the hive.
From the twenty-first day of its life until its death the bee works outside gathering pollen and nectar which it brings home to feed the community. It ends its life by falling exhausted, too old and tired to struggle back to the hive.
How bees find their way home
Bees make long flights from the hive, constantly changing their direction, and one might suppose that they would get lost, but they have several methods of finding their way. Firstly, they recognize landmarks near the hive. If the hive is moved during their absence the bees will return to the place where it previously stood. They certainly guide themselves by the sun, and in addition their compound eyes are sensitive to the direction of what is called polarized light, which comes in definite directions from the sky seen when the sun is obscured. Our eyes have no ability to distinguish polarized from ordinary light, but experiments have shown that many insects can do this, and use the ability to guide themselves.
A method of signaling
Bees have a special gland situated at the end of the abdomen, which gives out a scent, imperceptible to humans but a sign of recognition among bees of the same family.
When young bees go in search of nectar for the first time the older bees stand in a line on the threshold of the hive. They buzz their wings and keep their abdomens turned upwards, at the same time squeezing scent from their glands. This hangs in the air and gives their inexperienced younger sisters a guide to the way home.