AT least 500 caterpillars of the endangered small pearl-bordered fritillary butterfly have successfully hatched in the latest stage in a project to save them from extinction in County Durham.

The hatchlings are from eggs laid in captivity at Durham Wildlife Trust’s nature reserve at Low Barns near Witton le Wear and only small numbers of the insects survive in the county.

Captive bred butterflies , they came from butterflies sourced from County Durham and Yorkshire where existing population numbers of the small pearl are very good.

This pioneering butterfly captive breeding programme is being led by the Heart of Durham Project, supported by Durham Wildlife Trust, in conjunction with the Butterfly Conservation Trust, and it is now into its third year.

After last year’s wet and cold summer it was feared that many of these first generation caterpillars would not make it through the winter. However, several survived to emerge from the chrysalis in June.

David Wainwright, Butterfly Conservation Officer for the North-East, who has worked with the project team, said: “This fantastic number of caterpillars is extremely pleasing. However, the winter months will be the crucial period with weather conditions affecting how many will survive through to the spring.”

If conditions are favourable and sufficient numbers do survive, it could well mean that The Heart of Durham Project is a step nearer to re-introducing the small pearl-bordered butterfly to sites along the River Browney Corridor in County Durham, where they were once common.

Funding from the SITA Trust has enabled the Heart of Durham Project to work alongside landowners helping to bring areas of land back to conditions that are favoured by the small pearl-bordered fritillary by providing shelter from prevailing winds, plenty of marsh violets and nectar plants are the all important factors.