A butterfly that was once thought to be dying out in the UK has colonised Scotland.
The comma butterfly was in severe decline in the 20th Century and had become restricted to south east England and parts of the Welsh borders.
The UK population has now increased by 138% over the past 40 years and has spread as far north as Inverness.
Scientists believe its “extraordinary” success is due to climate change and the caterpillar’s nettle consumption.
Richard Fox, head of recording for the charity Butterfly Conservation, said: “The comma is clearly responding to climate change, which is driving its spread northwards.
“We have seen this in a number of other species that have spread up from England in to Scotland, but the comma is by far the most dramatic example.
“It now has spread not only through the whole of northern England but up through the Scottish Borders and Lothians, through Fife and Angus. It is now on the outskirts of Aberdeen and has been spotted in recent years near Inverness.”
He said the comma was once firmly associated with the plant hop and was sometimes nicknamed the hop dog.
“Although hop is still around as a wild plant, the mass agricultural growing of hop for brewing is much diminished nowadays,” he said. “It is also much more thinly spread in Scotland.
“But commas have become less dependent on hop and started to specialise on other things, particularly on the stinging nettle.
“Climate is driving the change but the comma has only been able to achieve this amazing spread north because it has become more specialised on stinging nettles, which are very widespread.”
The orange and brown-coloured comma – Polygonia c-album – takes its name from a white marking on its underside that is shaped like a comma.
With their wings closed, resting or hibernating adults are camouflaged against dead leaves, while the larvae, flecked with brown and white markings, resemble bird droppings.
The species has a flexible life cycle, which allows it to capitalise on favourable weather conditions.
Conservationists want the public to chart the progress of the comma during this year’s annual Big Butterfly Count.
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The world’s largest butterfly survey, which runs until 6 August, encourages people to spot and record 18 species of common butterflies and two day-flying moths across the UK.
The results will help track the ongoing spread of the comma and could shed more light on the population fluctuations of the butterfly.
Mr Fox added: “The comma is one of the Big Butterfly Count species that has bucked the trend and done well in Britain over recent decades. It may be even further north than we currently know.”
Although found in a wide variety of habitats, adult commas can be seen feeding on bramble, thistles and knapweed along canals and riversides. Their caterpillars feed upon nettles and hops in the same areas.
Sir David Attenborough, president of the BC charity, said: “Canals and rivers are fantastic locations for many species of butterfly.
“The comma is one of our most exquisite butterflies and hearteningly is also something of a butterfly success story.”
Those wanting to take part in the Big Butterfly Count should find a sunny spot and spend 15 minutes counting butterflies.
Records can be submitted online at www.bigbutterflycount.org or via the free Big Butterfly Count app.