When my husband and I were searching for gorillas in Nigeria, we worked in a forest that was full of bees. It was hot and humid, causing us to sweat copiously, which made us intensely attractive to the moisture-loving insects. Whenever we stopped in one place for too long, they would descend upon us, crawling all over our bodies, sucking up our sweat. At first, this experience was highly stressful for someone whose pet nightmare is being stung to death by an angry swarm. But these bees were not in attack mode. They were out foraging. They only stung us occasionally, when they got stuck under a bit of clothing. Had we made the mistake of approaching their hive, however, my nightmare might have come true.

These were the infamous African bees, a smaller, more aggressive cousin of the European honeybee, which is the kind we have here in most of the US. While African bees have no worse stings than do European bees, they are more prepared to use them, en masse, in a furious buzzing attack.

The spread of this insect out of Africa is now a familiar story. Since being introduced to Brazil in 1956, Africanized bees have spread rapidly throughout South and Central America and by 1995 had reached southern California.

The stinging attack of Africanized bees represents an orchestrated defense of their nest, and is a complex, military-like behavior. Some bees stand guard at the door, stinging any foreigners that enter the hive. Others fly out to attack approaching intruders. They have methods of recruitment as well. Stinging, an act of suicide for the individual bee, releases a chemical whose odor stimulates others to join in the attack. While all honeybees show this type of defensive behavior, Africanized bees are a lot touchier than their European cousins. Bee biologists recently pin-pointed one cause of this difference: it's in the DNA.

Professor Robert Page in the Dept. of Entomology at UC Davis, in collaboration with Greg Hunt from Purdue University, studied bees in Mexico where there are apiaries of both European and Africanized colonies. The researchers bred a fierce Africanized male, known as a drone, to a more laid-back European queen, a mixed mating that resulted in 172 descendent colonies. Scientists then examined these colonies for defensiveness. They waved a suede patch on a long pole in front of each hive entrance, and then counted the stingers that were left in the suede. The colonies varied in their ferocity, but the most aggressive plunged up to 150 stingers into the patch within 60 seconds.

The scientists then analyzed the colonies genetically. Previous work enabled them to recognize specific regions of DNA (which is formed into chromosomes) from both mild-mannered and hot-tempered bees. By tracing these regions through the offspring colonies, Page and his colleagues were able to link differences in the hives' stinging behavior to a particular stretch of DNA. In other words, bees that differed in their aggressiveness tended also to show genetic differences in this one region of a chromosome.

This is not to say, Professor Page points out, that they have discovered a "stinging gene" or, as it was recently phrased in the popular science press, a "mean gene". What they have found is a genetic "hotspot" for stinging behavior; a stretch of DNA that explains some of the differences in stinging tendencies between colonies. There could be many different genes involved: some might code for guarding the hiveís entrance; others for flying out to attack an intruder; others for responding to the smell of stinging comrades and joining the battle.

For Professor Page, a link between the genetics and the behavior of insects is nothing new. For example, through long and painstaking research involving everything from close behavioral observations to the collection of bee semen, Page has identified, specific regions of DNA associated with the way bees forage for nectar and pollen. He has shown how genetic features can influence the behavior of individual bees, which then determines the nature of the whole colony, which in turn influences the behavior of the individuals, and so on. Page and his colleagues are helping to answer one of the big questions in biology: how genes relate to complex society.

As for bee-keepers and the picnic-going public at large, understanding the genetics of stinging could prove useful one day, in the breeding of a kinder, gentler bee.

© Kelly Stewart

Dept. of Anthropology, University of California, One Shields Av., Davis, CA 95616
e-mail: kjstewart@ucdavis.edu

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