Lab and fieldwork combine to ensure Beauty moth is a little less rare
6 Jan 2025
An experimental combination of captive breeding and habitat management has seen one of the UK’s rarest moth species more than double its numbers at a key population site.
The scarce Dark Bordered Beauty’s previously most abundant year at the RSPB Insh Marshes site in Scotland saw it record 81 individuals two years ago.
But this year, late in the creature’s flight season, the species rendered a total of 176 specimens, substantially above anything recently achieved.
The onsite recordings were the work of one RSPB staff member on secondment: assistant warden Mick A’Court was working at the Scottish site on sabbatical from his normal workplace at the organisation’s Buckenham and Cantley Marshes and Sutton Fen reserves.
Additionally, a captive breeding programme of the moths is being directed by the Royal Zoological Society of Scotland at Highland Wildlife Park, using stock originating from Insh Marshes.
The aim is to produce eggs, larvae and adult moths for introduction into a selected sites to attempt to start new populations in other Scottish areas. Dark Bordered Beauties, identifiable by their orange-yellow colouring coupled with dark wing borders, are mostly based at a few sites in Scotland, plus one, undisclosed English location.
They are primarily associated with aspen woodland with the tree species, which rarely flowers or sets seed, relying for spreading upon suckering from tree roots that also provide a primary food source for the moth’s caterpillars. However, deforestation and grazing has impacted aspen populations and impacted the insect, requiring a focus on efforts at aspen woodland regeneration.
RSPB Insh Marshes warden Julie Ellis outlined: “We have ensured that there are areas available for the aspen to spread into by suckering. We have removed birch saplings in some areas, where they might out compete aspen suckers by keeping them in the shade, and have even cut aspen suckers to the height apparently used by caterpillars.”
Meanwhile, her colleague A’Court set up moth traps in different areas of aspen woodland at night during the Dark Bordered Beauty flying season. Trapped moths identified, counted and released in the morning totalled 12,058 moths from 212 species over the four-week period.
Among the Dark Bordered Beauty moths, some 34 moths (33 males and 1 female) were counted in a single trap – a notable increase from the previous record of 13.
Said A’Court. “It was astonishing to find 33 males and 1 female in a single trap. This is far in excess of anything caught in a single trap before. Quite why this apparent irruption in numbers occurred at the end of the moth’s flight season is unclear, but the final count of 176 moths does demonstrate that there is a good population at Insh Marshes.”
Photo: Shutterstock (Henrik Larsson)
