Win for Wildlife By Sally Welbourn
The marsh fritillary is one of the most interesting butterflies in Dorset and is the most attractive and colourful of the fritillaries. Often considered the ‘stained glass window’ of butterflies, they have small wings but are very recognisable with a bright, intricate pattern of white, orange and black markings. The damp grassland habitat, which is their main habitat, has been lost nationally due agricultural-improvement and drainage in the landscape. However, due to careful habitat management over the last 10 years, they have been found to be thriving on one of Dorset Wildlife Trust’s nature reserves, Bracketts Coppice. Dorset Wildlife Trust’s Living Landscapes Ecologist, Steve Masters said, “The most reliable method to record the numbers of marsh fritillaries is to count the larva webs in autumn or in spring after the winter hibernation. Eggs are laid in large batches, of up to 300, and the caterpillars aggregate in webs which can be counted relatively easily.” Marsh fritillaries prefer to hibernate in tussocks of grass as caterpillars (which are jet black in colour) and emerge in warm weather – as early as
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Ovenu February or March, if the winter isn’t too cold. Basking in the sun as caterpillars, they will then pupate and emerge as adult butterflies on the wing in late May, early June. These remarkable butterflies have a few challenges ahead of them including their loss of habitat, but also the parasitic wasp, which can be deadly to them by laying their eggs inside the caterpillar and devouring it. Steve continues, “Their food plant is Devils bit-scabious, and we have plenty of that at Bracketts Coppice. Marsh fritillaries love damp grassland, purple moor grass, and chalk, all of which we have in west Dorset. To help accommodate these butterflies we’ve adapted the management of Brackett’s Coppice slightly to ensure the
amount of grazing creates the right habitat for them, providing the right structure for all stages of their life cycle. We even removed one field from the previous hay cutting regime and grazed instead, and we were delighted to see marsh fritillaries breeding in this field for the first time, as a result.” These management techniques are being used on other suitable nature reserves, and in 2019, the highest number of marsh fritillary larval webs, since monitoring began, were found on Kingcombe Meadows nature reserve in west Dorset, with 38 being counted. Find out more about our nature reserves at www.dorsetwildlifetrust.org.uk