Photo top above by Martin Black (and header photo)

Photo above left by P Simmons

Photo above right by Caroline Walker

This is the largest of our Browns, although there is some size overlap between these and female Meadow Brown. In flight, it has been described as appearing “buoyant”, with the pale upperwing markings visible. This usually allows an observer to correctly distinguish between this species and Meadow Brown.

This butterfly always rests with its wings closed, so typically only the underwing is visible. However, during courtship, the male will flick his wings open and shut, or briefly hold them open, so a lucky photographer may obtain an upperwing photograph.

Upon settling, the underside of the forewing is often visible, showing the distinct eyespot on an orange background. If disturbed however, the forewings are tucked inside the hindwings; these show a mottled pattern of whites, greys, and browns, and provide excellent camouflage against the bare substrates on which the butterfly prefers to settle. Grayling also has the habit of leaning over when settled, although it is still unclear whether this is done to minimise its shadow or for the purpose of thermoregulation. On particularly hot days it will often stand on ‘tiptoes’.

It is sometimes stated that Grayling rarely feeds; this is not the case however, and it has been observed nectaring on Buddleia, Bramble (Rubus fruticosus), Crown Vetch (Securigera varia), Red Valerian (Centranthus ruber), and Wild Marjoram (Origanum vulgare).

The Grayling requires sites with sparse vegetation, sheltered, sunny spots, and areas of bare ground. In the Wolds, it is found on steep sided valleys with thin, well-drained soils, where grazing, combined with regular landslips maintain the required habitat. Elsewhere in the county these conditions are met on brownfield sites, disused quarries, and coastal dune slacks.

Each of these habitats face a variety of threats. Brownfield sites may be subject to plans for development; on Teesside proposals to develop the former British Steel land could lead to the loss of many hectares of ideal habitat for Grayling. Even if such land isn’t built on, it is often considered unsightly, and may be subject to inappropriate landscaping processes such as covering with topsoil and planting up with amenity trees. Elsewhere, natural succession reduces the amount of bare ground available if this is not kept at bay by suitable grazing regimes.

This was formerly the rarest butterfly in Yorkshire, as it was known from only a single site in the N. Wolds, in VC61. However, in 2001 it was discovered at a handful of sites on Teesside in VC62, primarily along the banks of the river Tees between Thornaby and Warrenby. Since this initial discovery the butterfly has spread to a number of new sites, possibly using the railway line as a corridor, and it can now be found on urban brownfield sites, sand dunes at South Gare, and the cliff tops near Skinningrove and Boulby.

Elsewhere in the county it has been found near Rotherham, on land adjacent to a steelworks, and in Wakefield there is a colony on railway land; when permission has been granted to survey this site some very high counts have been made.

None have been recorded from the N. Wolds site since 2016, and it may have gone extinct there.

Throughout the county there are likely to be large areas of suitable habitat along railway sidings and on industrial sites, which could potentially hold large populations of Grayling. However, the fact that most of these sites are inaccessible to the public means that if Grayling is present it will mostly go unrecorded.

This is a single brooded species, with adults typically emerging around early July and remaining on the wing until late August, but in some years the flight period can run from late June to early September.

Eggs tend to be deposited individually on clumps of grass surrounded by bare ground. Many grass species are used, including Sheep’s Fescue (Festuca ovina), Red Fescue (E. rubra) and on coastal sites Marram Grass (Ammophila arenaria). The eggs hatch after 10 to 20 days, and for the first 3 instars, the larvae feed mainly at night, spending the day hidden at the base of a tussock. During the third instar, they enter a winter hibernation period, below ground level or occasionally under stones. In spring, they go through 2 more instars before pupating around early June, in a silk-lined cell about 1cm below ground.

UKBAP status: Priority species

Section 41 species of principal importance under the NERC Act in England