‘Bee Perfume’ Could Ease the Sting of Invasion by Africanized Variety

Colorado scientists have developed a “bee perfume” that they say could be used to impede the invasion of highly aggressive Africanized “killer” bees into the United States.

Their discovery is based on the common chemical scent shared by bees in a hive, allowing them to differentiate between hive mates and strangers.

In their experiments, the scientists treated bees with the perfume and found that they were then more likely to accept each other as hive mates.

Based on this, the researchers suggest that it should be possible to remove the queen from an Africanized hive, treat the hive with the “perfume” and then insert a European queen treated with the same scent. The Africanized bees would then treat the European queen as their own, breeding with her and thereby genetically reducing the African bees’ aggressiveness. University of Colorado biologist Michael D. Breed and Glennis E. Julian report today in the British journal Nature.

“It’s virtually certain that beekeepers are going to have to be vigilant about keeping European queens in the (African) hive as a way to cope with the invasion of Africanized bees,” Breed said. The perfume “could prove to be an effective tool for re-queening.”

Breed’s idea is entirely plausible, said entomologist Gene E. Robinson of the University of Illinois. “The whole process of queen introduction is based on workers becoming habituated to the chemical signature of the new queen. Manipulating that process with new chemicals is entirely possible and opens up a new way of managing Africanized bee colonies.”

African honeybees were first imported by Brazil in 1957 by researchers at the University of Sao Paulo. A visiting beekeeper inadvertently let 26 swarms escape from captivity, and those swarms have multiplied into an estimated 2 million colonies living throughout South and Central America.

In the wild, the African bees have largely displaced their European predecessors. When the two strains have mingled, the African genes have predominated because the intermingling has usually involved African queens mating with European males.

The Africanized bees that have resulted from such intermatings are not as efficient as European bees at pollinating crops and they do not produce as much honey. Furthermore, when their hives are disturbed, the Africanized bees react very aggressively, stinging the intruder in much greater numbers than do European bees. The bees have killed countless wild and farm animals and some humans. Estimates of human deaths vary widely, ranging from 50 to 4,000.

Since their release in 1957, the bees have been spreading slowly northward. The first detected swarms crossed into Texas last year, despite the best efforts of scientists to control them. Experts fear that the arrival of the bees could have a disastrous effect on the $150-million-per-year U.S. beekeeping industry, as well as on agricultural production, which is reliant on the use of European honeybees as pollinators.

Bees are known to use a wide variety of chemical scents for communication. Especially important are those odors that identify a particular bee as being a hive mate or a stranger. Breed had previously surveyed a wide variety of organic chemicals similar to those found in beeswax to identify scents that had strong effects in hive-mate recognition.

Last year, he and Julian--then a Pomona College undergraduate employed in a summer program--tested the effects of two of the strongest chemicals, called hexadecane and behenic acid.

For each set of experiments, they took 110 newly emerged adult bees from a single hive and placed them in 11 boxes of 10 each. Five days later, after the bees had lost their normal hive odor, the scientists took bees from one of the boxes and, one at a time, placed them in the other 10 boxes, monitoring the response of the other bees. If the bees bit or stung the intruder within five minutes, the event was considered a rejection. If they did not attack the intruder, it was considered acceptance.

The researchers found that the likelihood of acceptance was significantly increased if the intruder and the defending bees had both been exposed to the same chemical before the intrusion. And they found that hexadecane provided the strongest response, overpowering other scents.

Based on these experiments, which did not include queens or Africanized bees, Breed suggests that the technique could be used to place European queens in African colonies. The researchers hope that continual breeding with European queens would allow the European genes to predominate over time.

Re-queening is routinely performed in colonies of European honeybees to keep the hive productive. Typically, the new queen will be enclosed in a cage and placed in the new hive for one or two days so that workers become used to her smell. She is then released. However, the process often fails, Robinson said.

Breed’s proposal represents the possibility of not only speeding up that process, Robinson said, but also of improving its efficiency.