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
Restricted to southern Britain with no records north of the Midlands and believed to be declining nationally. The small Cornish population has declined since 1997, although this may be more a result of under-recording.
In 1997 it was reported as occurring along the River Tamar above Gunnislake. There
have been no confirmed records of this species in Caradon since 1998 despite annual searching of previous breeding sites, but there are 2006 records from a few sites in North Cornwall on the upper reaches and tributaries of the Tamar.
Habitat & Ecology
Sites are confined to slow moving rivers or canals with lush marginal and floating
It is vulnerable to pollution and, especially, physical disturbance to bankside habitats.
Although this species may no longer occur in Caradon, further monitoring of known previous sites should continue. It is believed that the species is probably under-recorded.
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.