Ground Beetles of Ireland

Pterostichus nigrita

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Pterostichus nigrita
© Roy Anderson
Pterostichus nigrita
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(Maps updated 30th November 2009)

Pterostichus nigrita (Paykull, 1790)

Description: A moderately large (10-15mm) black ground beetle. Predatory. In 1988 it was realised that two species were included under this name, P. nigrita and P.rhaeticus, the two being separable only on structure of the genitalia. The present (nominate) species is widespread in lowland marshes and water margins.

World Distribution: A species recorded from the whole of Europe and Siberia to the Pacific Ocean, but probably conflated with its recent segregates, P. rhaeticus and P. mukdenensis Breit, in large parts of its range. True P. nigrita appears to be Eurosiberian Wide-temperate (64).

Irish Status: P. nigrita s.s. is widespread and common in the lowlands at least in the northern counties. Status elsewhere uncertain due to confusion with P. rhaeticus. In the map some southern records may refer to P. rhaeticus.

Ecology: A moderately hygrophilous species characteristic of wet riparian habitats in the lowlands, but also in hedgerows on heavy agricultural soils. Rarely recorded from oligotrophic peatlands or in exposed places on high ground.

Remarks: Two colour forms occur, one with reddish or reddish-testaceous femora (var. "rufifemoratus Stephens"), and the other uniformly piceous black. The red-legged morph occurs sparingly in Northern Ireland populations, but particularly those associated with ancient riparian habitats. Populations on agricultural land seem to lack the rufifemoratus trait and are very possibly not aboriginal. Individuals with the elytra as well as the entire legs testaceous or reddish-testaceous occur sparingly in a population occupying mesotrophic fens at Portmore Lough, Antrim (Anderson, 1993).