Rosy future for rare moth that hitched train ride
A RARE moth once thought extinct appears to be making a remarkable recovery at a Mid Wales nature reserve.
Rosy Marsh moths had not been seen in Britain for more than a century until one was spotted in Penrhyndeudraeth, Gwynedd, in 1965.
That prompted two years of fruitless searches in the area without a single moth being found.
But when the search area was widened, researchers struck gold 60 miles away at the Cors Fochno nature reserve, near Borth, Aberystwyth.
In 1967, a count there revealed 192 adult Rosy Marsh moths.
It was concluded the Penrhyndeudraeth moth had hitched a ride from Borth on the coastal railway line.
Annual surveys at Cors Fochno since 1988 have averaged 45 caterpillars: in 2017 only 19 caterpillars were found.
But this year’s count identified 123 caterpillars.
Jack Simpson, monitoring officer for LIFE Welsh Raised Bogs Project, said it was a “great result” – though still short of the record count of 155 in 2009. He said it was probable more moths were on the site as only a small area was surveyed each year.
“As a lowland raised bog, Cors Fochno is a stronghold for this species because of its abundant supply of food and its waterlogged, peaty soil,” he said. “The main food plant for the caterpillars on Cors Fochno is bog myrtle, of which there is an abundant supply.
“They also feed on crowberry and, occasionally, bog rosemary.”
The surveys take place at night as the caterpillars are nocturnal and spend the day underground to avoid bird predators.
Work is now being undertaken at Cors Fochno to improve habitats for the moths by cutting down trees and molinia grass.
Prior to its discovery on Cors Fochno in 1967 the last known UK site was a wetland in Cambridgeshire in 1850.
Most suitable wetland has since been lost. However the moth has been found at four other raised bogs in Ceredigion, including Cors Caron, and another site in south Cumbria.
The moth is also present at the Dyfi National Nature Reserve where, in 1986, the site’s bog myrtle was partly destroyed by fire.
No long-term effects were seen on Rose Marsh moth numbers, helping to disprove the theory it relied on frequent fires to generate new growth in its host plant.