Moths and butterflies

All three of these Focus Species rely on acid grassland habitats with bracken and violets. Violets are the caterpillar foodplant and bracken provides shelter and safe places to hibernate.  Q: should we separate out small pearl-bordered?

The heath fritillary is one of the rarest and most threatened butterflies in the UK. Between 1981 and 2019 its population declined by 90% and today it’s in danger of extinction.   

Heath fritillaries generally like sunny, warm, sheltered woodland glades with lots of common cow-wheat, the caterpillars’ main foodplant. They typically fly 1-2 km to new sites, although under the right conditions some may travel up to 5 km. Therefore they depend on stepping stones of suitable habitat.

They’re only found in a few sites in Kent, Essex, Somerset (Exmoor) and one site in Devon, a Butterfly Conservation reserve near Lydford where heath fritillaries were reintroduced in 2006, having gone extinct in the Tamar Valley due to habitat loss.  They’re found in the reserve’s open coppice woodland and nearby species-rich grasslands, where the caterpillars feed on ribwort plantain and germander speedwell. There have also been occasional sightings in the adjacent Forestry Commission woodlands. However, in 2024 only six individuals were recorded.

Dartmoor’s broadleaved woodlands support a group of rare moths which rely on microhabitats such as leaf litter, dead wood, oak leaves and fungi. The species in this group mainly have their strongholds in woodlands on the southern, eastern and south west fringes of Dartmoor. Sites such as East Dartmoor Woodlands NNR and Hembury Woods are especially important. 

These moths are often found in microhabitats such as dead leaves and under bark on dead wood.

Devon Species of Conservation Concern in this group include: Consultation Q: do we list these moths as below or is this too much information and we just link to the DSoCC spreadsheet?

• Banded goldenrod straw (Phalonidia curvistrigana) – Caterpillars feed on the flowers and seeds of goldenrod. Recorded in south east Dartmoor woodlands as well as woodlands in Torbay and Great Torrington.
• The coppice beauty (Olethreutes arcuella) – Caterpillars feed on dead leaves on the ground in Hembury Woods and other woodlands in east Dartmoor.
• Triangle (Heterogenea asella) – Caterpillars feed mainly on pedunculate oak and beech. Recorded in SW Dartmoor woodlands and Great Torrington.
• The lead-coloured pug (Eupithecia plumbeolata) – Recorded around the fringes of east, southern and west Dartmoor as well as west Exmoor. Caterpillars feed on common cow-wheat
• The blotched emerald (Comibaena bajularia) – Feeds on pedunculate and sessile oak. More widespread than some other species but declining and largely found in Dartmoor woodlands.
• The silver-streaked beauty (Schiffermuelleria grandis) – A very rare micro moth which thrives in humid woodlands where the caterpillars feed on decaying wood found under the bark.  It is currently found in the Teign Valley.
• Beautiful bark moth (Oecophora bractella) – Relies on dead wood and possibly fungi with records from Hembury Woods and southern Dartmoor.  This is a rare micromoth restricted to a few ancient woodlands in the midlands, south Wales and southern England. 
• Oak lutestring (Cymatophorina diluta) – Endangered and declining, feeds on oak and is found in Hembury Woods and other Dartmoor sites.

The Heckford pygmy moth has been listed as a Devon Special Species in its own right:

Devon’s heathland mosaics support a group of rare moths and butterflies. Some rely on species such as heather, gorse and broom. Others however have very particular microhabitat requirements which are not always recognised when carrying out habitat management for other more well known species. Devon Species of Conservation Concern which make up this group include:

Moths

• Neglected rustic (Xestia castanea) – a declining species which is dependent on heather. Found across the Pebblebed heaths and the eastern and SW fringes of Dartmoor.
• Grass wave (Perconia strigillaria) – caterpillars feed on heathers and broom. Found on the Pebblebed heaths and a few areas on the east Dartmoor fringes.
• Sandhill lead-miner (Phyllonorycter quinqueguttella) – found mainly on the Pebblebed heaths but also east Dartmoor fringes and Braunton Burrows. Caterpillars feed on creeping willow. 
• Small grass emerald (Chlorissa viridata) – now only found on heathland in the south of England. The main caterpillar foodplants are heather and birch but also gorse and creeping willow.  Recorded on the Pebblebed heaths, eastern fringes of Dartmoor and at Beaford Moor.

Butterflies

• Silver-studded blue (Plebejus argus) – add
• Grayling (Hipparchia semele) – add

 Four Devon Special Species are found in Devon’s wet acid grasslands.

The wood white is one of the UK’s lightest and smallest butterfly species. It lives in shaded and sheltered habitats with tall grassland or light shrub. Caterpillars feed on vetches, including bitter vetch, tufted vetch, birds-foot trefoil and greater birds-foot trefoil. Adults breed twice a year, flying in May or June and August.

In Devon, the largest populations are found in scrubby grasslands on the east Devon coast, Meeth Quarry in north Devon and Cookworthy Forest. The wood white typically stays in small, interconnected habitats, only flying 1 to 3 km and preferring woodland clearings.

Devon’s hedgerows and scrub provide essential habitat and connectivity for butterflies and moths. Species such as the lackey and lappet moths (both Devon Species of Conservation Concern) were once widespread across Devon’s farmed landscapes feeding largely on hawthorn and blackthorn. They are now more often found in coastal areas and nature reserves where habitat remains more suitable.

The brown hairstreak is considered one of the most elusive butterflies in the UK. Adults are rarely seen as they spend most of their time high in trees. They come down to lay eggs on young blackthorn leaves, often on warm south-facing hedges or scrub (so usually below 250 metres). Their UK population has declined significantly due to the loss of hedgerows and annual flailing. 

Devon is considered a stronghold and while they’re thought to be across the county more survey is needed. However, populations are known to be in the Blackdowns, Torbay and mid-Devon. The most effective monitoring method is counting eggs from late October to early March, when they can be seen on young twigs.  

The rich biodiversity of Torbay’s coastal limestone grasslands provides an ideal environment for a distinctive range of moth species that thrive in the wildflower-rich habitats typical of these well-drained soils.   Three species are listed as Devon Special Species in their own right. Two are discussed below. The beautiful gothic (Leucochlaena oditis) is found in a few other areas along the coast and is discussed in the north and south coast invertebrates group.

Two other Devon Species of Conservation Concern are an important part of this group:

• Little ghost (Ischnoscia borreonella) – Only recorded at Petit Tor Point and Berry Head in Devon and Portland in Dorset. Very little is known about this rare moth.
• Scarce moss moth (Bryotropha dryadella) – Recorded in three sites in Devon in Torquay, Berry Head and Hartland on the north Devon coast. Elsewhere it is known from Cornwall, Essex and Kent. It is very difficult to identify. Caterpillars feed on the moss Ctenidium molluscum.

See northern Devon sand dune invertebrates page for details.

To read more please go to the Sidmouth to Dorset coastal invertebrate group page. 

To read more please go to the North and south coast invertebrate group page.