Stingless Honeybees for Asia's Greenhouses
Scientists are developing bees which will pollinate crops without stinging the growers.
The common or European honeybee is widely distributed in Asia, as well as in Europe, Africa and the Americas. Common honeybees are good pollinators, but they have a painful sting. They are very protective of their hives, and will sting anyone who threatens them.
Because of this, most growers do not manage beehives themselves. They have to call in professional beekeepers. Sometimes they find that hives are not available when they need them.
Recently, scientists in Japan have been working to develop stingless bees. The bees are intended mainly for use as pollinators in greenhouses. Since there is no risk to the grower in handling them, it is hoped that eventually many growers may be able to keep their own hives.
Bees for Pollination
Pollination is a by-product of the bees' quest to produce honey. Bees fly out from the hive to collect nectar and pollen. As they move from one flower to another, some of the pollen is transferred. This fertilizes the flower, and enables to develop into a fruit.
Stingless honeybees have a rather small forage area. They have a flight range of only about 200 m, which means that they are never far from their hive. This makes them very suitable for greenhouses. In contrast, the flight of the common honeybee may cover more than 2 km.
It is important that bees chosen to pollinate a crop are attracted to that kind of flower. The common honeybee will forage on a wide range of crops (more than 80% of cultivated plants). Scientists are still working out which plants are favored by different species of stingless honeybee. The Australian stingless honeybee, Trigonia carbonaria, is a promising species. It is known to be a good pollinator of macadamia trees. It also quickly adapts to new plants it has not encountered before.
Bees for Honey
Honey is made from the nectar which is gathered from flowers. The bees put the nectar in a honeycomb cell and fan it with their wings to evaporate the water. When there is less than 18% water in the nectar, the mixture is then called honey.
The common honeybee is a good producer of honey. It evolved in a temperate climate and stores a lot of honey for the winter. A good hive might produce 30-40 liters of honey.
Stingless honeybees also store honey, but not as much as common honeybees. For example Trigonia carbonaria produces only 800 ml (less than a liter) of honey per hive each year. Only half this small amount can be taken by the beekeeper. The rest must be left for the bees or they will die.
There is a long history of keeping stingless bees, going back to the ancient Mayan civilization of South America. Mayan beekeepers were harvesting honey from stingless honeybees more than a thousand years ago!
Tropical Honeybees in a Cold Climate
All stingless honeybees come from the tropics. If they are to spend the winter in a temperate country like Japan, they must be kept warm.
Japanese scientists have recently developed a heated beehive for stingless honeybees. The hive consists of two boxes. The bees live inside the inner box, which is usually made out of wood. The inner box has three compartments: one for feeding, one for food storage, and one for the brood. The outer box is insulated, and contains a heating element and a heat sensor. This keeps the hive at a constant temperature, even in the middle of winter.
The Life of Bees
Honeybees are social insects. The adults cooperate with each other in caring for the brood and building the nest. A small hive of common honeybees might contain around 20,000 bees. Stingless honeybees tend to live in smaller colonies. The number of stingless honeybees in a hive ranges from a few hundreds to a few thousands.
The hive has a single queen, who lays all the eggs. Nearly all the bees in a hive are female worker bees. They do not lay any eggs, but they do all the other work of the hive. They secrete wax which they use for building the nest, with storage cells for honey ("honey comb"), pollen and the young larvae.
They fly out of the hive and visit flowers in search of nectar and pollen, which they bring back to the hive. They also collect resin from trees, which they make into propolis.
Wild colonies of both common honeybees, and stingless honeybees usually build their nests in a cavity in a tree. While common honeybees make their cells from wax, stingless honeybees make them out of cerumen. This is a mixture of wax and propolis. In some species, the cells are built into the form of a flat spiral (see cover photo).
The nest also contains a few males ("drones"). Once in her lifetime, the queen will mate with one of these. Bees form new colonies by swarming. At swarming time, the queen leaves the hive with drones and worker bees.
Among common honeybees, it is the old queen who leaves. In hives of stingless honeybees, it is the young virgin queens who fly away. Typically, the workers of stingless honeybees search for a site and get the new hive ready before the young queen arrives. The connection between mother and daughter may last for months.
Common honeybees are cold-blooded, but they are able to maintain the temperature of their hive at 32OC. Stingless honeybees lack this ability. In the wild, they do not have any colonies in areas with cold winters. To overwinter in a cool climate, they need some form of heating.
The Stingless Honeybee
Stingless honeybees resemble ordinary honeybees, but lack a functional sting. There are 400 species of bees which have evolved without a sting. Recently, ordinary honeybees without functional stings have been bred by using gamma radiation. They are a kind of mutant. They are sometimes referred to as artificial stingless honeybees, compared to naturally stingless ones.
Artificially Stingless Honeybees
Common honeybees can be genetically altered to be stingless. One method is to expose queen bees to strong gamma radiation (20-50 Gy). About a quarter of these queens will produce broods with 1% stingless bees. The stingless trait is inherited, so it is possible to establish a strain of non-stinging honeybees by breeding and selection.
Another way is to expose the larvae to gamma ray radiation (30 Gy) just when they are changing into pupae. If this is done, around 97% of the honeybees when they emerge will be stingless.
Naturally Stingless Honeybees
Different species of stingless honeybee are found in tropical South and Central America, tropical Asia and the north of Australia. They tend to prefer pollen as a food to honey. Whereas common honeybees collect mostly nectar from flowers, stingless honeybees collect mainly the pollen. This means that stingless honeybees are very good pollinators.
Index of Images
Figure 1 Hive for Stingless Honeybees so They Can Overwinter in Japan. Wooden Inner Box on Right, Heated Outer Box on Left.
Figure 2 Stingless Honeybee about to Land on Flower
