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.
Range & Status
This species occurs in Cornwall and west Devon, the New Forest areas of Dorset and Hampshire and south-west Wales. Colonies are noted to undergo considerable fluctuation and may disappear from sites undergoing seral succession. There has been a decline in West Cornwall, but it remains a stable species in the east.
The two significant populations in Cornwall occur in the derelict tin mining areas of West Cornwall and the upland areas of Bodmin Moor.
Habitat & Ecology
The species has a strong preference for shallow water with little vegetation; valley mires and earth extraction sites are classic habitat. Such habitat is prevalent on Bodmin Moor where grazing and trampling by stock maintains suitable areas. Similarly, the Red River Valley near Camborne has ideal habitat as vegetation is slow to re-establish around old tin stream workings.
Once vegetation is allowed to establish itself, populations of this species will die out. Reclamation or filling of old tin/china clay extraction sites will pose a threat. Sites have been lost in the west Cornwall since 1997.
The species is a ' key site' indicator and strongholds should be monitored. Any work on derelict mining extraction sites should take this species habitat requirements into account; this is considered important with regard to the future proposed development of the china clay workings in mid Cornwall.
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.