Wildlife lovers are being asked to head to their local canals and riversides this summer to chart the astonishing progress of the comeback kid of the butterfly world.

The Comma has experienced a 138% increase in population over the last 40 years despite being rare just a century ago.

The Butterfly Conservation now want people to head to the riverside and count how many Comma Butterflies are in their areas as part of a national campaign.

The best way to spot the Comma is to find a sunny spot with bramble, thistles or knapweed nearby and spot the butterfly, distinguishable by its distinctive ragged wing edges for 15 minute periods.

Butterfly Conservation President Sir David Attenborough 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. Help conservationists track the Comma’s expansion by looking out for it by canals and riverbanks during this summer’s Big Butterfly Count.”

At the turn of the 20th century the Comma, with its distinctive ragged wing edges, was restricted to a few counties in the Welsh borders and south-east England.

But just 100 years later the Comma has spread throughout the UK with climate change and an increase in nettle plants as food supplies being attributed to the cause of its re-emergence.

Mark Robinson, National Ecologist for Canal & River Trust, said: “Canals and rivers are great places to spot many species of butterfly. The Canal & River Trust would encourage everyone who lives near to one of our waterways to visit and discover all the amazing wildlife that thrives on our 2,000 mile network and take part in the Big Butterfly Count.”

Richard Fox, Butterfly Conservation Head of Recording, said: “The Comma is one of the Big Butterfly Count species that has bucked the trend and done well in Britain over recent decades. Even it is susceptible to changes in the environment so we need to continue to monitor its progress, especially after a worse-than-usual year in 2016. By taking part in the Big Butterfly Count you can help us keep tabs on the Comma and other common butterflies.”

Counts can be logged on the Big Butterfly Count website www.bigbutterflycount.org or through the event’s app.