Cyprian honeybees kill their enemy by smothering them

September 17, 2007

For the first time, researchers have discovered that when Cyprian honeybees mob and kill their arch enemy, the Oriental hornet, the cause of death is asphyxiation. They reported their findings in the September 18, 2007, issue of Current Biology, a publication of Cell Press.

"Here, for the first time we detail an amazing defense strategy, namely asphyxia-balling, by which Cyprian honeybees mob the hornet and smother it to death," said Gérard Arnold of CNRS in Gif-sur-Yvette, France. "The domestic bee has never ceased surprising us."

Previous studies showed that Asian honeybees similarly attack hornets, leading the predatory insects to die from the heat inside the ball of bees. That murderous "thermo-balling" strategy is used against invaders, mainly hornets, armored with a hard cuticle that is impenetrable to the bees' most familiar weapon: their stingers.

However, scientists knew from earlier studies that various subspecies of the domestic honeybee (Apis mellifera), which form comparable balls around hornets, couldn't raise the temperature high enough to finish off the heat-tolerant hornets, explained the study's first author, Alexandros Papachristoforou of Aristotle University of Thessaloniki, Greece. It had been shown that the mobbing bees go for the gut, targeting the hornets' abdomen, which is critical for the insects' ability to breathe. By pumping their abdominal muscles, the hornets bring in air through small openings called spiracles, which are covered by structures known as tergites when air is released.

To find out whether the bees could be blocking the hornets' breathing, the researchers monitored their respiration under normal conditions and those designed to mimic the balling behavior, in which they covered either two or four of the insects' tergites. The hornets' respiration declined by about 33 and 87 percent, respectively, in these experiments.

Next, they tested whether the bees could kill hornets whose tergites were held open with tiny plastic blocks. They found that the bees took twice as long to kill such manipulated hornets.

"To kill the high-temperature-tolerant hornet, Cyprian honeybees have developed an alternate strategy to thermo-balling and stinging," Arnold said. "They appear to have identified the hornets' 'Achilles heel' by asphyxiating the predator. This ability indicates that under extreme conditions, honeybees can present a high level of adaptation in order to survive."
The researchers include Alexandros Papachristoforou, Andreas Thrasyvoulou, Georgia Zafeiridou, and George Theophilidis of Aristotle University of Thessaloniki; Agnès Rortais, Lionel Garnery, and Gérard Arnold of Laboratoire Evolution, Génomes, Spéciation, CNRS UPR9034.

This work was partly supported by the bilateral program ZENON, the Research Promotion Foundation of Cyprus and the Greek program HERAKLEITOS (EPEAEK).

Papachristoforou et al.: "Smothered to death: Hornets asphyxiated by honeybees." Publishing in Current Biology, 18 September 2007, R705-R796.

Cell Press

Related Bees Articles from Brightsurf:

Two pesticides approved for use in US harmful to bees
A previously banned insecticide, which was approved for agricultural use last year in the United States, is harmful for bees and other beneficial insects that are crucial for agriculture, and a second pesticide in widespread use also harms these insects.

Native bees also facing novel pandemic
There is growing evidence that another ''pandemic'' has been infecting bees around the world for the past two decades, and is spreading: a fungal pathogen known as Nosema.

Bees grooming each other can boost colony immunity
Honeybees that specialise in grooming their nestmates (allogroomers) to ward off pests play a central role in the colony, finds a new UCL and University of Florence study published in Scientific Reports.

Microalgae food for honey bees
A microscopic algae ('microalgae') could provide a complete and sustainably sourced supplemental diet to boost the robustness of managed honey bees, according to research just published by Agricultural Research Service scientists in the journal Apidologie.

Bees point to new evolutionary answers
Evolutionary biology aims to explain how new species arise and evolve to occupy myriad niches -- but it is not a singular or simplistic story.

Quantifying objects: bees recognize that six is more than four
A new study at the University of Cologne proves that insects can perform basic numerical cognition tasks.

Prescribed burns benefit bees
Freshly burned longleaf pine forests have more than double the total number of bees and bee species than similar forests that have not burned in over 50 years, according to new research from North Carolina State University.

Insecticides are becoming more toxic to honey bees
Researchers discover that neonicotinoid seed treatments are driving a dramatic increase in insecticide toxicity in U.S. agricultural landscapes, despite evidence that these treatments have little to no benefit in many crops.

Neonicotinoids: Despite EU moratorium, bees still at risk
Since 2013, a European Union moratorium has restricted the application of three neonicotinoids to crops that attract bees because of the harmful effects they are deemed to have on these insects.

Bees 'surf' atop water
Ever see a bee stuck in a pool? He's surfing to escape.

Read More: Bees News and Bees Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to