Butterfly Conservation Dorset is asking people to visit historic Maiden Castle near Dorchester this bank holiday weekend to record butterfly sightings.
The wildlife charity are concerned that common species normally found at the Iron Age hillfort, like the Brimstone may have completely disappeared.
The sulphur-coloured Brimstone was once a commonly seen butterfly at the site, but has not been spotted there since 2010.
They are often spotted in gardens in pairs and always sit with their wings closed. The male’s wings are a clear yellow, but the female can be identified by her slightly paler upper wings, which have a green tint.
Dorset County Butterfly Recorder Bill Shreeves, said: “It’s really important that we have fresh records so we can see what’s going on at Maiden Castle. As well as being one of the largest Iron Age hillforts in Europe, it’s home to a number of butterflies, including the rare Adonis Blue and Dingy Skipper.
“They seem to being doing okay, but we’re extremely concerned about the lack of sightings of our common species.”
If you spot any butterflies at Maiden Castle, please record it here. Any sightings you submit will need to include the map grid reference for the area, which is: SY6688 and SY6788.