May 13, 2009 > TechKnow Talk: Bees: Living the Hive Life
TechKnow Talk: Bees: Living the Hive Life
Where would we be without bees? Their service as pollinators produces many of our fruits and vegetables and as a bonus they give us honey. But the bee population is in severe decline worldwide. How do bees make honey and pollinate our crops, and why are there fewer of them around?
Honey has been consumed by humans for thousands of years. It has been found in Egyptian tombs, still edible, and was so highly prized in ancient societies it was sometimes used as currency.
Honey is composed almost entirely of sugar and water. The sugars are primarily fructose and glucose. These are simple, readily-digested sugars offering carbohydrates for quick energy. Though honey is a tasty sweetener and an excellent source of carbohydrates, it is not "the perfect food" some people believe. It provides no significant amount of vitamins, minerals, or other nutrients.
Honey does have the amazing property of essentially infinite shelf life. Stored in a relatively dry environment (such as an Egyptian tomb), it will keep pretty much forever. It may "sugar" or granulate into a solid material, but is easily returned to its liquid state with heat.
This resistance to spoilage is due in part to honey's low moisture content and acidity, both of which deter bacterial growth. In addition, bees add an enzyme to the honey that combines with glucose to create hydrogen peroxide and other chemical agents repellent to bacteria.
Bee-like pollinators have been on Earth for at least 100 million years. Today, there are more than 10,000 species of bee. Many of these are "social" insects, living in hives or colonies. Bees are distinguished from closely-related insects such as wasps, hornets, and yellow jackets by their diet. Bees feed on pollen and honey. These other flying, stinging insects are carnivorous, eating mostly other insects. Though they do not produce honey and are unwelcome at picnics, they too provide a great service to mankind by consuming pests that would otherwise damage our crops.
Bees are also characterized by two sets of wings and hairy bodies designed to gather pollen. The bee domesticated for the production of honey is the European honeybee. A healthy hive of honeybees may contain 40,000-80,000 individuals. These are of three types: queen, drone, and worker bees.
Each type of bee plays a different role within the hive. There is only one queen, a fertile female whose sole purpose is to lay eggs. Drones are male bees; they have no stingers and serve only to mate with the queen. When no longer needed for this purpose they are ejected from the hive. Most of the bees are workers; these infertile females perform all the functions necessary for the maintenance of the hive.
Workers gather pollen and nectar. They also defend the hive against invaders. Some workers become "nurse bees," dedicated to feeding the young bees, or larvae. Workers also regulate the hive temperature, providing ventilation via thousands of flapping wings in hot weather and clumping together to conserve heat when it's cold.
A honeycomb is composed of hexagonal wax chambers or cells. In the case of domesticated bees, the beekeeper places a template sheet of wax into a frame to help the bees begin a well-structured honeycomb. The queen lays one egg per cell. She is capable of laying both fertilized and unfertilized eggs. Fertilized eggs develop into worker bees; unfertilized eggs become drones. The queen may lay as many as 2000 eggs a day during late winter and early spring.
The egg hatches into a larva in just a few days. The larva resembles a maggot, and consumes tremendous quantities of protein-rich pollen and honey for several days. It then spins a cocoon and the cell is capped with a wax plug by the nurse bees. The adult bee emerges about a week later, ready to go to work. During the summer, the queen may continue to lay hundreds of eggs a day, to replace workers lost to predators or old age.
Most of the workers spend the warm summer days seeking nectar, the sugar-rich liquid flowering plants use to attract pollinators. They are able to communicate the direction and distance to a good source of nectar to other workers using complex "dances." As the bees use their long tongue-like proboscis to drink the nectar inside the blooms, they also collect pollen from the stamens and become unwitting pollinators as they move from flower to flower.
Once back in the hive, the nectar is regurgitated. This material, mixed with enzymes from the bee's stomach, is honey. Honeycomb cells not being used for nurseries are available for storage of honey and pollen. This food is required for the larvae during the spring and summer, and to provide sustenance for the workers during the winter months.
The beekeeper harvests in summer or early fall, when the combs are packed full of honey. The honeycomb is often replaced with a container of sugary liquid to ensure the bees survive the winter. It is then shaved to remove the caps, and the liquid honey is extracted. At this point, it will contain particles of wax, as well as some eggs and larva. The honey is filtered to remove these impurities and bottled for sale.
If the queen becomes ill, dies or if the hive becomes too crowded, a second queen will be produced. This is accomplished by feeding one of the larva "royal jelly," pollen enriched with secretions from a gland in the nurse bee's head. When the new queen emerges, she will immediately seek and destroy any existing queen.
If the old queen is healthy, she will take thousands of her strongest workers and leave the hive in search of a new home before her successor emerges. The new queen will assume her position in the hive, and begin mating and rebuilding the strength of her colony.
The old queen and her retinue form a swarm. These are often seen hanging from a tree branch while waiting for scouts to find a suitable home. While so many bees may seem scary, a swarm is not aggressive and will typically not sting unless attacked. Beekeepers try not to allow a hive to become so strong it swarms, as they will likely be left with an under-producing hive until it restores its numbers.
In the last 30 years, the number of both domesticated and wild honeybees has been declining. The decline appears to have accelerated dramatically since 2006. Some estimates place the number of hives today at less than half the number in 2005. No one knows why this is happening; there may in fact be several contributing causes.
Bees have always been victimized by other insects, mites, and viral diseases. There is evidence that mites and disease in particular are accounting for some losses, but not sufficient to explain the observed reductions. Some researchers blame environmental changes such as global warming and loss of flowering plant habitats to human encroachment, but these factors alone seem too gradual to explain the sudden rate of decline.
Some experts are now focused on the impact of pesticides on the health of bees. Many agricultural operations rely on bees trucked in to pollinate the fields. Moving from field to field may cause higher levels of pesticide exposure than the bees would encounter if left in one place, foraging among a variety of both natural and cultivated flowering plants.
Whatever the reasons for their decline, bees as pollinators are critical to our food supply as well as to the propagation of other plant life. Hopefully the trend will be arrested or even reversed before the planet and its inhabitants suffer the result of too few of these industrious creatures.