Cornish Biodiversity Network  -  Supporting Wildlife Recording

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Cornish Red Data (2009)

The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.

Glaucopsyche arion - Large Blue

Range & Status

The Large Blue became extinct at the last known British site (in Devon) in 1979; the penultimate site was in Cornwall on the north Atlantic coast, from which it disappeared in 1973. It has now been re-established in Britain using stock from Sweden on sites in the south-west, where it has been doing very well, colonising new areas. There are some 15 colonies in Devon, Somerset, Gloucestershire \endash and now Cornwall, where it was reintroduced in 2000.

Regional Distribution

The Large Blue was found in a number of colonies on the north Atlantic coast of Cornwall, an isolated colony in West Penwith and possible colonies at Land' s End and elsewhere. Potential re-establishment sites are on the north Atlantic coast. The butterfly was reintroduced to a National Trust site at Dannonchapel, when 12 adults (10 females and two males) were released, followed by 300 larvae. Since then, adults have been observed every year, ranging from 53 in 2001 to 24 in 2007, when it was estimated that 1750 eggs were present on site. Sightings were down in summer 2008 (as bad weather restricted survey time) but the population appears to be fairly stable.

Habitat & Ecology

Detailed studies of the ecology of the Large Blue have been made by Jeremy Thomas (Thomas, 1980; 1994). In Britain, the Large Blue occurs on warm, well-drained unimproved grassland, where it depends on the red ant Myrmica sabuleti for its survival. The number of M. sabuleti nests present depends partly on the amount of short turf available. Climate change may have an effect on the habitats chosen by M. sabuleti , which are likely to move to cooler sites if temperatures increase.


Threats to future Cornish colonies are likely to centre on practical difficulties associated with management regimes and climatic conditions. Future re-establishments will be on suitably protected land are already planned.


The present re-introduction plan includes the establishment of a viable network of colonies (Barnett & Warren, 1995). The re-establishment programme is co-ordinated by the Joint Committee for the Re-establishment of the Large Blue Butterfly. Listed on Schedule 5 of the Wildlife and Countryside Act 1981, the Large Blue is an endangered species in Europe and its world status is vulnerable (IUCN, 1990). A UK BAP priority species.


I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.

The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.

Cornish Biodiversity Network. 2017.