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Honeybees 'buzz off' tramp ants
By Jody Bourton
Earth News reporter

An attentive honeybee sends an ant flying (shown in real time, then in slow-motion). The ant is positioned below the bee and flies off to the right

Honeybees use their wings to 'blow away' marauding ants that venture too close to their nests.

Scientists in South Africa and China have captured this unique behaviour on film for the first time.

As the ants approach, the bees turn in circles and fan their wings with a force greater than when in flight.

This produces such a large force that individual ants can be blown off their feet, the researchers report in the Journal of Insect Behavior.

Cape honeybees (Apis mellifera capensis) are found in southern parts of South Africa.

It's like using a leaf blowing machine to blow away grass and leaves
Ming-Xian Yang
Rhodes University, South Africa

Their nests are often invaded and damaged by a host of other insect pests, including tramp ants (Pheidole magacephala) hive beetles (Aethina tumida) and the greater waxmoth (Galleria mellonella).

But the researchers only came across the bees' defensive tactic by accident.

"I dropped some honey at the entrance of a honey bee colony by mistake," says Mr Ming-Xian Yang, a biologist at Rhodes University, Grahamstown in South Africa and Yunnam Agricultural University in Heilongtan, China.

"It was not long before the ants came, then guard bees started fanning immediately when they detected the ants."

So along with colleagues from both universities, Mr Yang investigated the behaviour.

Blown away

Further study using video analysis and sound recordings to measure wing beat frequency revealed that the bees were using their wings as a fan to blow away the ants.

"It's like using a leaf blowing machine to blow away grass and leaves," Mr Yang told BBC Earth News.

When coming into contact with the ants, the bees spin 360 degrees, both clockwise and anticlockwise, in a bid to dislodge the ants en mass.

This approach allows the bees to increase the area of counter-attack and reduce the chance of ants passing into the nest.

The research team also recorded the wing beat frequency of the fan blowing and found that it was significantly greater than the bees use in normal flight.

That means the defence tactic costs the bees significant amounts of valuable energy.

While this fan-blowing behaviour has been reported before, it has not previously been filmed.

The researchers have also uncovered how the bees select from a range of defensive techniques depending on the type of pest they are trying to eject.

For example, bees also use the fanning technique to blow away aphids and termites.

However, they physically push smaller hive beetles away using a 'mauling technique', while the larger larvae of the greater waxmoth are seized with mandibles and thrown from the nest.

The researchers hope their findings will lead to a greater understanding of the co-evolutionary arms race between bees and pests such as ants.

They also hope to identify other bee species around the world that exhibit similar behaviours.

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