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.

Hydaticus transversalis - A diving beetle

Range & Status

Extant populations centred on the Somerset Levels, Norfolk Broadland and a few other fen sites in England, also the Gwent Levels. Foster (1985) provides a national distribution map.

Regional Distribution

There is a single record in the 1960' s from a water tank at Peninnis Head, St. Mary' s

(Mackechnie-Jarvis, 1969).

Habitat & Ecology

Most frequently associated with ditches in grazing levels that are rich in emergent and submerged macrophyte vegetation.


Loss of habitat through drainage and agricultural improvement, lowering of water tables through water abstraction schemes (may not be relevant to the Isles of Scilly).




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.