For centuries, they have clashed with and repelled repeated foreign invaders from Vikings to the mighty Roman Empire.

Now Scotland’s native honeybee is the latest species to come under threat from a foreign invasion as the country’s growing number of beekeepers bring non-native bees to fill their hives.

Experts say a gradual “diluting” of the DNA of the native bee fear it could become as rare as pure native wildcats through breeding with non-native species.

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Last year, a new charity called the Scottish Native Honey Bee Society (SNHBS) was established to help protect the indigenous species and convince more keepers to convert their colonies to native bees.

Now it has launched an initiative to help measure and track native species across the country.

The project's coordinator, Ian Lennox said: "We want to find as many colonies of native bees in Scotland as we can.

"What we're trying to do is based on the premise that if you can't measure it, then you can't manage it."

Environmentalists have spoken of the increasing threat of non-native species on Scotlands indigenous wildlife, with the likes of Himalayan Balsam smothering river banks, grey squirrels and mink all having an impact on Scotland's ecological health.

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Experts say the Scottish bee, also called the European Dark Honey Bee or Apis mellifera mellifera, is hardier than other species which makes them more suitable to the Scottish climate.

Imported bees, which are often bought in from Holland, France, Germany or Italy, are more readily available but carry a greater risk of bringing in disease from the Varroa mite, they say.

They also risk cross-breeding with the native species creating hybrids.

The SNHBS is encouraging both hobby and commercial beekeepers to submit pictures of their stock to be identified by a team of experts.

They will then follow up with DNA tests on those that visually resemble the Scottish native dark bee.

The aim is to establish more native hives that will be available to widen the gene-pool for breeding purposes with swarms on Scottish Government protected areas, such as the islands of Colonsay and Oronsay.

Mr Lennox, who has kept bees for more than 40 years, said that an increase in interest in beekeeping was benefitting from a boon across the country, it was a "double-edged sword".

He said: "I have my own 'mongrel' bees, as do most of the beekeepers in the UK.

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"But the situation is getting worse.The more beekeepers there are, the more demand for bees there are ."

He said that the greater demand meant that commercial suppliers see bringing in imported bees as more lucrative, as they are cheaper and more readily available,

Beekeeper Matthew Richardson, who is apiary manager at the University of Edinburgh, said: "There's two issues, one is that we're diluting the native genetic stock.

"Imported honey bees, such as from Italy, may be more productive in a good year, but may be less successful in a bad year and suffer more during the winter and aren't as suited to the climate.

"So we generally encourage people to always try and keep local bees wherever possible and what the SNHBS is promoting is as a way of preserving good native stock that is suited to the climate.

"The other problem with imports with bees coming from Europe and beyond, is that there is a risk of an infiltration of diseases and pests."

He added: "Because people are getting much keener on keeping bees and getting involved, beekeeping has changed quite a bit in the last 20 or 30 years.

"You used to pretty much be able to get some bees, put them at the bottom of your garden, leave them and collect some honey at the end of the year.

"Now there are threats and diseases, climate change, it's more of a hands on management kind of situation.

"But as people become get better informed and more aware of the risks and they're able to manage them, it becomes an easier problem to deal with.

"This is where the things like the SNHBS are really working to try and prevent the next generation of pests and diseases and problems for beekeepers before they arrive."

A Scottish Government spokesman said: "We welcome this initiative by Scottish Native Honey Bee Society and agree it is important to protect and conserve Scotland’s native honey bee population.

He added: "Through our Pollinator Strategy and our 10-year Honey Bee Health Strategy we are working with the Scottish Beekeeping Association and the Bee Farmers Association to achieve a sustainable and healthy population of honey bees for pollination and honey production.”

Full instructions on how to enter the survey are given on the SNHBS website