Loch Arkaig's pine forest. Credit: John MacPherson. Image provided by Scotland Woodland Trust.
Loch Arkaig's pine forest. Credit: John MacPherson. Image provided by Scotland Woodland Trust.

WW2 commando training site sees remarkable ecological discoveries

6 min


Nearly 1000 species of insects identified in key study in the Highlands 

A tenacious ecologist has identified 946 species of mostly flying insects in a West highland wood – and he’s still counting!

Dogged dipterist Ian Strachan’s marathon microscope effort began with samples taken five years ago at Loch Arkaig Pine Forest in Lochaber.

The study is thought to be the most thorough ever conducted in a Western pinewood in Scotland’s rainforest zone. Experts say it shows the amazing biodiversity of the habitat. It also highlights the extraordinary tenacity of a man with a passion for nature.

Loch Arkaig Pine Forest was bought by Woodland Trust Scotland and local group Arkaig Community Forest in 2016.

Funding raised by players of People’s Postcode Lottery has contributed to the purchase of the site and the ongoing restoration work.

‘This is a quite remarkable piece of work, and we applaud Ian Strachan’s extraordinary tenacity,’ says Laura Chow, Head of Charities at People’s Postcode Lottery.

‘Flies might not seem as glamorous an area to work in as say birds of prey or wildcats, but they are just as important.’

‘These findings will help us understand the amazing biodiversity of these woods and will guide restoration efforts in the coming years – we’re delighted support from our players continues to assist with this.’

Various baseline surveys were commissioned to assess what was in the wood – including birds, fungi and lichens. Ian from nearby Roy Bridge was commissioned to survey the insect life.

Separating and identifying individual species

‘The minute you say West highland insects most people think of the dreaded biting midge,’ explains Ian.

‘Many will be amazed just how small a component those and other biters like clegs are in the scheme of things. There is much more buzzing around at Loch Arkaig than biting midges, though they do have a particular talent for making their presence felt!’

Ian took his first samples from two locations in the forest in 2018 using Malaise traps – tent-like contraptions that funnel flying insects into a jar of preservative alcohol.

He then set about the laborious task of separating out and identifying individual specimens under a microscope. 

By the time he had sent in his first report in 2020 he had identified 316 species, including two fungus gnats entirely new to the UK, including Boletina gusakovae, which is usually found in Finland and Russia and Mycetophila idonea which heralds from Estonia, Poland, Slovakia, Georgia and Luxembourg.

Since then, Ian has continued to work his way through the rest of his original 2018 samples. 

His species total from those has now reached 650. In addition, some further samples were taken in 2021 using techniques including sweep netting and water traps. This has added a further 219 species to Ian’s list. 

The grand total to date is 946 invertebrate species made up of 869 flying insects including midges, dance flies, hoverflies, fungus gnats, barkflies, mayflies, stoneflies, dragonflies, alderflies and caddis flies.

Specimens awaiting identification

There are also 77 non-flying species to add to his tally. These mainly consist of spiders but they’re also including millipedes, centipedes, woodlice, springtails and ticks.

Ian is still counting. It could take years to ID every smudge and smut in his samples which contain tens of thousands of individual specimens. He reckons he may be only two thirds of the way through the mass of preserved insects.

The Malaise trap samples have been sorted to at least family level but individual insects sometimes sit in jars at the National Museum of Scotland waiting until the right expert can be found to name their species.

Specimens of fairy wasps have been sent to the Natural History Museum in London and are awaiting identification. These tiny parasites lay their eggs inside other insect eggs and are the smallest insects known to science.

For other tricky groups Ian has turned to specialists from across the country for help, including members of the Malloch Society (Scottish fly enthusiasts).

In a few cases he has had to look abroad and even contacted Professor Massimo Olmi in Milan who was able to identify tiny pincer wasps based on samples provided to him.

Meanwhile word of Ian’s marathon effort is spreading around the international scientific community. He sent specimens of biting midges to Canada where world expert Dr Art Borkent is writing an identification key.

‘This has been a really challenging but satisfying process, investigating the remarkable insect diversity of these woodlands,” says Ian.

‘My findings are attracting a lot of interest from other entomologists and ecologists. I am not aware of a more exhaustive study ever having been carried out in a Western pinewood.’

‘I am grateful for the support of my son Alasdair and a host of insect enthusiasts, notably Iain MacGowan and members of the Malloch Society and the Highland Biological Recording Group.’

Findings scheduled to be presented to Edinburgh conference

Ian will be giving a talk about his findings to the annual meeting of the Dipterists’ Forum to be held in November at the National Museum of Scotland in Edinburgh.

Of the species found in the survey so far at least 50 are considered Rare or Scarce in Britain, with almost a third of them included on national Red Lists as Vulnerable or Threatened.

Some of Ian’s most exciting finds have been dance flies (Empids). He found five females of Anthalia beatricella, one of the smallest British species at just 1.7mm long.

This is the first record for Scotland. It was first described in 1992, from Windsor Forest, and is known from just three other sites in England and one in Wales.

The larvae are thought to live in rotting wood – dead and decaying timber is an important habitat for many of the insects found.

He found three other rare dance flies, including: Tachypeza fennica, the third British record (these were previously recorded in Wester Ross and Sutherland).

He also discovered a single male of Chelifera angusta which is only the second record for Scotland along with a pair of Platypalpus rapidoides (the third Scottish record).

The lance fly Lonchaea deutschi was also collected in one of the traps in 2018 and is only the second record for Britain.

Sites location for WW2 military training – and Hollywood filming

British Commandos and Allied Special Forces including the Free French trained at Loch Arkaig during World War Two. 

The loch was also a filming location for a sequence in Harry Potter and the Deathly Hallows.

In the scene, Harry, Hermione and Ron cling to a dragon as it flies above the forest before jumping off into the Loch below. It’s believed filming on the loch shore had to be cut short because the midge onslaught was so fierce!   

Woodland Trust Scotland and Arkaig Community Forest bought the woodland site in 2016 from Forest Enterprise Scotland under the National Forest Land Scheme.

The aim is to restore native woodland habitats and re-connect local people with the management and stewardship of the site.

They hope to use the woods to underpin sustainable rural development in the nearby communities of Achnacarry, Bunarkaig and Clunes. 

Imagery kindly provided by Scotland Woodland Trust. Main photograph: John MacPherson.

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