Marsh Fritillary

As Naturetrek’s representative, I was pleased to accept the invitation from Butterfly Conservation to attend a guided visit to a reintroduction site in north-east Hampshire for this scarce and beautiful UK butterfly.

The visit was the culmination of a 7-year project involving Butterfly Conservation (BC), Natural England (NE), the Hampshire and Isle of Wight Wildlife Trust (HIWWT) and the Ministry of Defence (MOD), on whose land the reintroduction took place.

The species once had a scattered distribution across north-east Hampshire but steadily declined through a combination of the drainage of its preferred wet grassland habitat, building construction and neglect. It was finally lost from this MOD land in the early 1990s due to lack of suitable habitat management.

A survey of possible reintroduction sites carried out by Butterfly Conservation indicated that the MOD site had the greatest potential for re-establishing the species to one of its former haunts.

The site has several contiguous meadows stretching for around one mile and of varying degrees of wetness. HIWWT implemented grassland management using cattle to break up the dominant tussocks of Molinia grass and Juncus species to create a mosaic habitat where the grass tussocks are interspersed with flowering plants such as Meadow Thistle (Cirsium dissectum), Tormentil (Potentilla erecta) and Heath Spotted-Orchid (Dactylorhiza maculata). These are all important nectar species for the adult butterfly but most importantly it created ideal conditions for the growth of Devil’s-bit Scabious (Succisa pratensis), the larval food-plant.

Meanwhile, BC were granted a licence to collect larvae of the butterfly from six sites with strong populations around Dartmoor in Devon. No more than 10 caterpillars were taken from each larval web to maximise genetic diversity. These were then used to initiate a two-year captive breeding programme with the larvae feeding on enormous quantities (6,000 plants) of Devil’s-bit Scabious provided by a horticultural supplier, yet another partner in the project.

With the habitat successfully restored, the first batches of larvae were able to be released. The larvae gather together in the grass tussocks and spin a silken protective web around themselves for the winter. They emerge on sunny days in January or February, basking on dead grass, before feeding up during March and April. After pupation the adults emerge in mid-late May. This year the first emergence was recorded at the site on the 14th May and on our visit we were delighted to observe around 20 adults still on the wing.

In addition, we were shown batches of eggs laid on the underside of the leaves of the most robust Devil’s-bit Scabious plants, generally those with a south-facing aspect. The eggs are yellow when laid but gradually darken to brown and hatch after 2-3 weeks.

The restoration of the meadows has not only benefitted the Marsh Fritillary but has also created habitat for a range of species including other butterflies, moths and dragonflies as well as a diverse flora.

It is still early days in the reintroduction process but all the signs are that the Marsh Fritillary may once again have a bright future in this corner of Hampshire.

Naturetrek continues its long-running support of Butterfly Conservation with a ten per cent donation of the proceeds from our dedicated butterfly tours going directly to support the conservation of British and European butterflies. To see our selection of butterfly tours, each led by an expert butterfly enthusiast, please click here.