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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.

Plebejus argus - Silver-studded Blue

Range & Status

Confined mainly to the lowland heaths and calcareous grasslands of southern England with large populations in Hampshire and Dorset, but also occurring along the North Wales coast in large numbers. The ten year population trend in England and Wales to 2004 shows a decline of 72% (Fox et al ., 2006). Widespread in temperate Europe through Asia to Japan. Populations are declining in some western European countries and there is some expansion in south-east Europe and Russia (Asher et al ., 2001).

Regional Distribution

In Cornwall, this species is mainly coastal with the large populations on the towans at Perranporth and Gwithian and smaller colonies on coastal heaths (Wacher, Worth & Spalding, 2003). It also occurs on inland heathlands. New colonies have been recently found at Dannonchapel (2004) and The Dodman (2006) so there may be further unrecorded colonies.

Habitat & Ecology

Lives in close-knit colonies in two different habitats; sand dunes and heaths. A mosaic is required of bare sand or earth and close cropped vegetation where most larvae occur, along with longer vegetation for shelter. The larvae feed on Bird' s-foot Trefoil Lotus corniculatus on dunes and heathers on heathlands, and are attended by ants.


Loss of early successional habitats with the encroachment of scrub and subsequent loss of bare ground, which affects not only the larvae but also the Lasius spp. of ant, which attend the larvae and pupae. Pressure groups objecting to grazing on coast and heaths could result in further loss of suitable habitat. Wet summers may cause flooding of the ant colonies and loss of pupation sites (Wacher, Worth & Spalding 2003).


Maintenance of suitable open habitat with grazing at, for example, Penhale SAC (where it was introduced for a short time in 2005) and scrub cutting by volunteers at Breney Common nature reserve. A UK BAP priority species.

Click here to see Aphotoflora images by David Fenwick


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.