INCREDIBLE footage shows a Scottish castle covered in a cloud of mayflies so thick it looks like a snow blizzard.
The terrifying scene was filmed at the weekend at Loch Leven Castle, where Mary Queen of Scots was imprisoned.
Visitor Andy Leech caught the remarkable scene as the mayflies – which live for one day – emerged from the water and took the skies in their millions.
The top of the historic building is almost obscured by the cloud of insects and some unfortunate tourists swallowed them.
The amazing clip shows the massive swarm almost obscuring the top of the castle.
Andy, 24, a student photographer from Kirkcaldy, Fife, said: ” I have never seen anything like this before.
“They only have a one-day lifespan and what you see in the video is the only day they will be alive. Basically they live for one day only to breed.
“The flies hatch from the water after being under the surface for a year. They also make very little to no noise.”
Despite the blizzard like appearance of the creatures, Andy added the bugs weren’t causing too many problems with visitors.
He continued: “They were not actually causing a problem for people apart from maybe being a mild annoyance by accidentally going in people’s mouths.
“Fortunately these do not bite because they have no mouth, as they literally live to mate and nothing else.
Posting the short clip online Andy wrote “Extreme M?i?d?g?e?s?! (May Flies)” with over 100 people commenting on the rare sight.
Henrietta Holmes Blair wrote: “I thought it was snowing. Lol. Wow.”
Kirsteen Watson said: “I’m getting itchy just looking at them”
Dougie Begg commented: “Well it is May after all, and in numbers like that it’s a sign it’s going to be a long hot summer.”
Karen Allan responded: “I was there yesterday.I can confirm I was truly demented by the huge swarms of flies.”
Mayfly hatchings happen in late spring and early summer and only emerge from the water to breed, but die shortly afterwards as they don’t have a digestive system.
The rare insect can live for years under water as a mayfly nymph – an immature version of the bug – and are unique among insects as they have two adult phases.
The Island on Loch Leven was where Mary Queen of Scots was imprisoned and is a popular tourist location.