EIGHT new arrivals have set hearts aflutter among wildlife experts as a project to save an endangered butterfly takes off.

Last month, 40 caterpillars were secretly released at a site as part of an effort to save the small pearl-bordered fritillary, which is on the verge of extinction in County Durham.

Now, Durham Wildlife Trust has confirmed eight have already emerged and it is hoped others are well on their way to transforming into butterflies which will boost the numbers of the threatened species.

Anne Porter, Heart of Durham Project Officer, said: “This is brilliant news and represents a major step forward for the project”.

The caterpillars were released several weeks ago at an undisclosed site alongside the River Browney, which feeds into the River Wear near Durham.

The release of the caterpillars, all of which were bred in captivity by naturalists, was the result of three years’ worth of work as part of The Heart of Durham Project, a partnership between Durham Wildlife Trust and Northumbrian Water.

The aim is to gradually restore landscapes and habitats in the North East into such a state so to allow wildlife to thrive, focussing particularly on land between Derwent Reservoir and Hamsterly Forest specifically.

Once abundant in the North-east , by 2006, it was estimated that only six colonies of the small pearl-bordered fritillary remained in the region, with their number having dropped by 93 per cent since the mid-nineteenth century.

The Project has planted more than 6, 000 marsh violets, the food plant for the caterpillars, and nectar species, such as ragged robin, bugle and devils-bit-scabious, in sites in County Durham.

Over the next few years, the butterfly will be introduced onto sites in the west of the county.

In September 2013, the Heart of Durham Project rejoiced as at least 500 caterpillars, only a few millimetres in length, hatched from eggs laid in captivity.

These eggs were laid by butterflies which had themselves been hatched at Durham Wildlife Trust’s nature reserve at Low Barns, near Witton le Wear.

Funding of £120,000 for the project was provided by the SITA trust.