Description: A medium-large (13-15mm) very shiny black ground beetle with rounded pronotal angles. Occurs on muddy or peaty soils in very wet bogs and fens. Very local but widespread.

NI account: Widespread but extremely local and rather rare, though perhaps less so in northern counties. Johnson & Halbert (1902) quote a single record for Cork. In the 20th century it has been reported from Armagh (O'Mahony (unpublished); specimen in the National Museum of Ireland, Dublin), Cloverhill, Cavan (Nicholson, 1914); Ardagh, Killarney District, Kerry (Bullock, 1932b); Lough Derg, Clare (Mackechnie Jarvis, 1971); and Belle Lake, Waterford (Anderson, 1991). Long extinct in the East Anglian fens, its survival as a British insect rested for a time on an adventitious colony in the New Forest of Hampshire, which is now believed to have died out (Hyman, 1992). In recent years, Day (1987) trapped specimens in the extensive fen/cutover bog complex at Brackagh Moss National Nature Reserve, Armagh and a survey of fens in south Down and Armagh (Nelson 1998) has added six other sites (Nelson & Anderson, 1999). Irish localities now total about eighteen.

Ecology: Habitat data suggest that this is an extremely hygrophilous species, and confined to particular kinds of wet humus soils in eutrophic or mesotrophic fens. There are no records for raised or blanket (ombrotrophic) bogs, except where peat-cutting has brought about the regeneration of fen conditions. In the absence of human interference, it appears able to exist only in the early successional stages of raised bog formation, before contact with mineral-rich ground water is lost. It has been recorded from a saline biotope in the Azores (Borges, 1996), but is otherwise a stenotopic freshwater wetland species.

Distribution: A Eurosiberian Boreo-temperate species (54), found locally across west and central Europe to 62°N, but mainly in the east, and into the western part of Siberia. There are outlying populations in the mountains of north Africa.

Similar Species: Pterostichus aethiops: duller; elytra with 3 non-foveate inter-strial punctures P. madidus: duller; elytra with 1, exceptionally 2, inter-strial punctures

Key Identification Features:

• Large species, glossy black
• Pronotum with hind angles completely rounded (Fig. 60)
• Elytra with 3 or 4 strongly foveate inter-strial punctures

Distribution Map from NBN: Pterostichus aterrimus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Pterostichus aterrimus at iNaturalist World Species Observations database.

GBIF data for Pterostichus aterrimus | Classification: Insecta, Coleoptera, Carabidae, Pterostichus

Thumbnails for genus Pterostichus