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Honey-bees are known for their sting, but scientists have now discovered they can also bite.

Bees resort to biting when faced with pests, such as parasitic mites, that are too small to sting.

Close study of the biting behaviour has revealed that they secrete a chemical in their bite that stuns pests so they are easier to eject from a colony.

Tests suggest the chemical could also have a role in human medicine, as a local anaesthetic.

Stun tests

Dr Alexandros Papachristoforou, a biologist at Greece's Aristotle University of Thessaloniki told the ����ý honey-bees had previously been seen dealing with pests that lived alongside them in colonies but this had always thought to be part of their grooming behaviour.

"Everybody thought that was it. Full stop," Dr Papachristoforou said. "But that's not the case. It's something totally different and was just there and we could not see it.

"I think we know too many things about the pathology of honey bees," he said. "We are still missing a lot of basic knowledge on their biology and behaviour."

The pests that honey-bees bite include varroa mites as well as wax moth larvae.

The varroa mite is endemic throughout both feral and cultivated honey-bee colonies.

If the population of mites in a hive is left unchecked they can sap the strength of workers, making them much more susceptible to viruses, disease and other debilitating conditions.

Wax moth larvae burrow through the comb in hives gradually destroying the cells where broods are raised and honey stored.

The knock-out effect of the chemical secreted in the honey-bee bite, known as 2-heptanone, was discovered as Dr Papachristoforou and colleagues observed bees dealing with pests.

Dr Papachristoforou recovered wax moth larvae that had been ejected from a hive, assuming the bees had killed them. Instead, he said, the larvae had started wriggling again soon after being ejected.

Before now bees were thought to secrete 2-heptanone as an alarm pheromone to tell other colony members about a potential threat.

However, said Dr Papachristoforou, this had never seemed an entirely satisfactory explanation because 2-heptanone was so volatile that it quickly lost its potency. In addition, he said, bees had at their disposal a much more powerful chemical alarm signal.

To stun pests, the 2-heptanone is injected at the site of the bite a bee inflicts on a mite, moth or larvae.

Early tests suggest 2-heptanone may also find a role in humans as a local anaesthetic. It could be an alternative to well established treatments such as lidocaine that can provoke allergenic reactions in some people.

"The potential implications of this new research for honey-bees and their interactions with varroa mites and wax moth larvae will need to be looked at in more detail, but the initial results look really interesting," said Giles Budge, senior researcher with the UK's National Bee Unit.

"I think it is amazing that despite all the years of intensive study there are still massive discoveries to be made about fundamental honey-bee physiology such as the ability to paralyse small insects and mites," he said.

Dr Papachristoforou, said the good news about the research was that bees would not inflict any damage on humans if they bit them.

"Humans cannot be bitten by bees," he said. "They have such small mandibles they can only use them against larvae and mites."