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Spring 2006 - Bees

Destination Purdue > Spring 2006 - Bees

DNA could hold the key to aggressive bee-havior

By Julie Douglas

Americans eat about 275 million pounds of honey each year, or about a pound for every person, according to the National Agricultural Statistics Service.


Photo provided by Scott Bauer, USDA Agricultural Research Service

An Africanized honeybee (left) and a European honeybee. Despite color differences between these two bees, normally they can’t be identified by eye.

Beekeepers' colonies were in danger of being overtaken by Africanized honeybees, also known as killer bees, until Purdue University's Greg Hunt found a solution. Killer bees have been migrating to parts of the southern United States from Mexico. They are now found in parts of Texas, New Mexico, Arizona and southern California. Killer bees produce less honey, are aggressive and are more easily agitated than their European honeybee cousins.

Hunt, a Department of Entomology bee specialist, worked with a team of researchers to locate the aggressive gene in the Africanized honeybee. "Locating this gene helps researchers understand why Africanized bees are so aggressive," Hunt said. "Now we know how to reduce these killer bee colonies and will not have a loss in honey production."

Gentle bees are important for agriculture, because one-third of the food produced in the United States comes from plants pollinated by honeybees. Where killer bees have become established, many beekeepers quit because the bees are so aggressive.

What causes an attack of killer bees?
By Julie Douglas

A disturbed Africanized beehive can stay agitated for several days. When one bee stings, it releases a banana-like scent that angers other bees in the colony. Once angered, Africanized bees:

  • May attack any threat within 100 feet, and may pursue threats for a quarter mile.
  • May perceive loud noises, strong odors or fragrances, shiny jewelry and dark clothing as threats to the colony.
  • Usually attack the face and ankles.

Hunt and his colleagues created a genetic map of the honeybee using the same techniques used in crop genetics. This map has important implications for beekeepers. "This allowed us to breed selectively for gentle bees," said Hunt.

His lab has been trying to identify honeybee genes that influence colony defense. Hunt found that the genes influencing whole-colony stinging behavior also make individual bees more likely to guard the colony entrance. Guard bees check "IDs" by using their antennae to smell other bees, keeping out robber bees who try to steal honey and alerting the hive to sting other intruders.

"Honey production decreases when these aggressive bees mate with our honeybees, which originally came from Europe," Hunt said.

Hunt and his colleagues found the "mean gene" in Africanized bees by measuring the speed and intensity of stinging behavior in 162 colonies of genetically different bees. Then, they located DNA markers in the aggressive hybrid bees and compared them to the genes of nonaggressive hybrid bees. The next step included isolating the gene for further study, said Hunt.

"It is interesting to speculate what causes worker bees, which cannot reproduce, to undertake these tasks to help the colony. If a worker bee stings you, she is giving up her life for the hive," said Hunt.

Through research and gene mapping of the honeybee, Hunt's research is helping stabilize honey production and decrease the aggressiveness of colonies, which allows for easier handling and honey collection.