Identifying common heathland butterflies and moths

Why heaths are butterfly and moth country

Heathland is one of Britain's oldest and most surprising landscapes. It looks sparse, even bleak, yet it supports an extraordinary concentration of insects. The reason lies in its structure: a mosaic of ling, bell heather and cross-leaved heath, broken by bare sandy patches, gorse scrub, bracken and patches of sallow or birch. Warmth matters enormously. Dark heather absorbs heat and bare ground radiates it back, creating little pockets of microclimate where insects can complete their life cycles in a short British summer.

That combination of warmth, low-growing food plants and open, sheltered ground is exactly what many of our scarcest butterflies and moths need. Learn a handful of species well and a walk on a heath in July becomes far richer.

Silver-studded blue

The silver-studded blue is the emblem of lowland heath and a genuine speciality. Males are a deep violet-blue with a fine dark border; females are brown, often dusted with blue near the body. The underside is where the name comes from: greyish-brown with rows of black spots ringed in white, and, near the outer edge of the hindwing, a row of tiny metallic blue-green scales — the silver studs. They catch the light like sequins.

Flight is mainly from late June through August, with a single brood across most of its range. It lives in tight colonies, sometimes numbering only a few dozen adults, and rarely wanders far. The caterpillars feed on heather — ling and bell heather especially — but also take gorse, bird's-foot trefoil and rock-rose. The species depends heavily on black ants, which tend the larvae for the sugary honeydew they produce and shelter the pupae in or near their nests.

Other heathland butterflies to look for

• Grayling. A master of disguise: mottled brown and grey, resting on bare ground with wings closed, often tilted to face the sun. Flight from July to early September. Grasses, especially sheep's fescue, are the food plant.
• Small heath. Small, pale orange-brown, with a weak, fluttering flight. On the wing from May to September in overlapping broods. Caterpillars feed on fine grasses.
• Green hairstreak. The only British butterfly with a green underside. It sits on gorse and bilberry blossom in April to June, when its colour makes it almost impossible to spot until it moves.
• Dingy skipper. Fast, darting and moth-like, grey-brown with pale spots. Look for it from May to August on bird's-foot trefoil growing in short, sunny turf.

The emperor moth

The emperor is our largest native moth and a heathland headline act. Males fly fast and low in sunshine, especially on spring afternoons, quartering the ground as they follow scent trails left by females. Their forewings are grey-brown with pale bands, but the hindwings are a glowing orange-pink, each marked with a bold eyespot ringed in black and cream. Females are larger, paler and mostly nocturnal, and they seldom fly until after dark.

Expect adults from April to May in southern Britain, running later into June in the north. Caterpillars are unmistakable: plump and green, banded with black and yellow, and studded with pink tubercles. They feed on heather, bramble, sallow, blackthorn, hawthorn and birch, then spin a pear-shaped brown cocoon low in the vegetation, where it can be found on heather stems in winter.

Night-flying specialists and other heathland moths

• True lover's knot. A dark purple-brown moth with crisp white markings, strongly associated with heather. Adults hover at heather flowers at dusk between June and August, and the larvae feed on ling itself.
• Beautiful yellow underwing. Small and day-flying, purple-brown and marbled with white, flashing yellow-orange hindwings when disturbed. Food plants are ling, bell heather and cross-leaved heath. Look in June and July.
• Fox moth. Males patrol on sunny May and June afternoons in search of wingless-looking females. Larvae are the famous dark, woolly "hairy caterpillars" seen crossing tracks in autumn, feeding on heather, bramble and sallow.
• Oak eggar and northern eggar. The northern form is a true heathland moth in the north and west. Males fly rapidly by day; females fly at night. Heather, bilberry and sallow are the food plants.

Food plants and how to help

Nearly everything on a heath comes back to a small group of plants. Ling, bell heather and cross-leaved heath feed the silver-studded blue, true lover's knot, beautiful yellow underwing and emperor. Gorse and bilberry carry green hairstreak and oak eggar. Fine grasses such as sheep's fescue support grayling and small heath, while bird's-foot trefoil keeps dingy skipper and silver-studded blue colonies going. Sallow, bramble and birch add variety and nectar.

If you help look after a heath, aim for a mosaic rather than a uniform carpet of heather. Rotational cutting or burning on a long cycle, light grazing, and the retention of bare patches and scrub edges all benefit insects. Leave some mature heather standing through winter, keep a few sallow bushes, and avoid clearing every last bramble.

For recording, a slow walk on a warm, still morning is best for butterflies. Moths are easier after dark: a light trap run overnight, or a torch shone on heather flowers at dusk, will often produce true lover's knots and emperors. Send your records to your county moth or butterfly recorder — heathland colonies are small and scattered, so a single well-recorded visit can genuinely matter.