The Marsh Fritillary Butterfly was last seen on Turraun Bog in 1995 but has been recorded back on the bog within the past week.
That's according to Bord na Móna whose ecologists have confirmed the butterfly's return to the area.
Head of Bord na Móna’s Ecology Department, Joe Lane, said this is a discovery of major European significance.
"The Marsh Fritillary Butterfly is a rare and beautiful creature that we thought had disappeared but now we now know to have returned," Mr Lane commented.
"We believe it has returned because of the extensive bog rehabilitation work that has taken place in Turraun and at the nearby Lough Boora Discovery Park but we need way more data on this project. That is why we are making a big appeal to people to go out there and find more examples of this and other butterflies."
Mr Lane is directing the public to the website www.bordnamona.ie where a picture of the Marsh Fritillary is posted so people know what to look for.
"We are asking people to photograph butterflies if they can and send the picture and details regarding the location to us at email@example.com.
"We know they are out there, so we are asking people to take their children, family, friends, grannies, whoever they can get to come to Lough Boora Discovery Park or go out to bogs and wetlands and help us find them. Above all when you do go out looking for the Marsh Fritillary remember to have fun and stay safe”
The Marsh Fritillary is the only Irish butterfly that is protected at a European level. It is a species that lives in wetlands and bog margins.