Once assembled near the recent Education Centre and newly-created pond, the warden Mark Allen gave us an introductory talk. The reserve was established 10 years ago and comprises a mosaic of habitats over 73 ha, including marshy grassland, neutral and acid grasslands, and an area of ancient woodland. This site is above a former mine, and Mark told us how the coal board had to fill in a series of bell pits that had formed ponds, after a horse had disappeared down one.
No less than 25 species of butterfly have been recorded at Aberbargoed Grasslands (out of a total of 59 species in the UK). The reserve is particularly important for marsh fritillary (Euphydryas aurinia), one of Wales’s rarest butterflies, which favours damp pastures where its larval food plant devil’s bit scabious (Succisa pratensis) can be found. The silk webs spun by the larvae are counted in the autumn as a way of monitoring the marsh fritillary population. The caterpillars overwinter buried in the grass tussocks, emerging in spring to again feed on devil’s bit scabious leaves. After pupation, the adults are on the wing for only around 4-8 days.
Although a little overcast, we had great success in finding and photographing marsh fritillary, along with a number of other notable butterflies, such as the small pearl-bordered fritillary (Boloria selene), along with an elephant hawk moth and other insects.
Management on the reserve involves grazing using native breeds of cattle, and scrub and pond management by rangers and volunteers. This creates the conditions for a spectacular community of grassland plants to flourish, most characteristically the purple moor grass and rush pasture. On our visit, masses of heath spotted orchid (Dactylorhiza maculata) were to be seen.
An autumn visit is best for seeing the fungi, for which this reserve is also of national importance, especially for waxcaps.