Numerous recent sightings of a moth that became extinct in the UK in the 1960s, suggest that it has recolonised and is now breeding across southern Britain.
Now, however, experts believe that the moth is beginning to breed again with sightings of the creature having been reported both in Suffolk and over the border in Norfolk.
The moth has a wingspan that can reach almost 12cm and a bright blue stripe across its black hindwings, it has long been considered a holy grail by conservationists.
Richard Fox, from the charity Butterfly Conservation, said: “The Clifden nonpareil is a fantastic addition to our wildlife and it is great to know that it is resident again in the UK, after an absence of 40 years or so.
“Its caterpillars feed unnoticed up in the canopies of aspen and poplar trees, so the adult moths are the best indication of how widely established this species now is.
“There’s never been a better chance of a thrilling encounter with this impressive insect.”
People are being asked to record sightings of the Clifden nonpareil and other moths as part of the annual Moth Night, which runs from September 26 to 28.
Mark Tunmore, founder of Moth Night, said: “September is a special time for studying moths in the British Isles, with a colourful range of resident species mixing with more exotic species from Europe or even North Africa as warm air currents sweep them northwards.
“Already this year, we have received reports to our migrant insect news service, Flight Arrivals, of Clifden nonpareil sightings from Cornwall, Devon, Sussex, Warwickshire, Suffolk, Dorset, Kent, Norfolk, Somerset and Northamptonshire.