RARE BLUE BUTTERFLY NOW THRIVING IN ITS FORMER HOME

By Mark Collins

Naturalists who, for two consecutive years, relocated three dozen Silver-studded blue

butterflies from Buxton Heath to Broadland Country Park, near Horsford in Norfolk, are

thrilled that these beauties are once again thriving in their former habitats after an absence

of more than 60 years.

Releasing Silver-studded blue butterflies in Broadland Country Park. Credit: Hans Watson

The Silver-studded blue, Plebejus argus, is a lovely but scarce and delicate species that has

been lost from over 80% of its former habitats in the past century, as heathland has

gradually been converted into forestry and housing. It is a nationally protected species, and

in Norfolk can now be found flying at just four locations. The project described here required

permission from Natural England, along with essential backing from the Norfolk Wildlife Trust

(NWT), which manages nearby Buxton Heath, and Butterfly Conservation, which monitors

butterfly translocations nationwide.

The reintroduction site at Broadland Country Park is situated on a gentle, sunny slope in a

small valley, with a stream flowing through woodland to Felthorpe Common and eventually

into Hors Beck, a tributary of the River Bure that flows through the Broads National Park.

This site was the source of butterflies that were, many years ago, successfully introduced to

nearby Horsford Rifle Range, where they have since become extinct. Other populations

were successfully established at NWT Buxton Heath, East Ruston Common, and Kelling

Heath. However, the original source population at what is now Broadland Country Park, was

wiped out in the 1950s when plantation forestry took over. With substantial areas of trees

since removed, Bell heather, Erica cinerea, and black ants, Lasius niger, which the

butterflies need to complete their life cycle, have returned, raising the possibility that the

Silver-studded blue could come full circle and be brought back to thrive once more in its

original home.

The Silver-studded blue has a remarkable life cycle. After mating in June, the females lay

eggs that overwinter among Bell heather to hatch into caterpillars the following spring. They

grow plump on the heather leaves and begin exuding a sweet secretion that prompts black

ants to protect them and take them down into their underground nest. Here, safe from

predators and parasites, they pupate and are finally released by the ants as adult butterflies.

Mating Silver-studded blue butterflies. Credit: Hans Watson

A team from the Norfolk and Norwich Naturalists’ Society, led by Mark Collins, carried out a detailed survey to ensure that the essential black ants were present in high numbers, and

the heather was in good enough condition for the leaf-feeding caterpillars and the nectar-

feeding adults. It was always going to be touch-and-go whether the butterfly would survive

after such a long absence from the site. Still, after the initial reintroduction in June 2023, a

new generation of at least a dozen adults were recorded in June 2024.

Another tranche of adults was introduced in that year, and now, in 2025, a new generation of

at least fifty individuals has been seen, having spread much more widely across the

regenerating heathland. There are high hopes that the population at Broadland Country

Park, with the essential help of the resident black ants, will now continue to thrive without the

introduction of additional adults from Buxton Heath.

Dave Weaver, an award-winning community volunteer naturalist at the Country Park and a

key member of the NNNS team, has been carefully observing the situation. He will continue

to monitor for at least five years and, given the high numbers on the wing so far this year, he

believes the stage is set for a very successful future. It will increasingly attract visitors and

provide a wonderful sight for them at the Country Park.

Alan Dawson, who monitors the Silver-studded blue and other butterflies at the source site,

Buxton Heath, agrees that the butterfly is once again thriving at Broadland Country Park,

and it was clearly the right time to take some individuals back to their restored home there,

creating a fine example of nature recovery in progress. The Park was established by

Broadland District Council just a few years ago and has become a popular destination,

particularly for local residents. With careful management, this will be a flagship site for nature

recovery and biodiversity conservation in Norfolk.

During a three-year research project, the Norfolk and Norwich Naturalists’ Society has

identified more than 2,500 species of plants and animals at Broadland Country Park, and the

return of the iconic Silver-studded Blue to its former home is a moment of great pride for all

concerned. It is remarkable that the Silver-studded blue and their friendly black ants, after

living apart for more than 60 years, have so easily rekindled their wonderful and mutually

beneficial relationship.

Dr Mark Collins was Chair of the Research Committee of the `Norfolk and Norwich

Naturalists’ Society and is now Chair of the Broads Society. Both photographs are credited

to Hans Watson.