Ground Beetles of Ireland
Pterostichus oblongopunctatus
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 © Roy Anderson |
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Pterostichus oblongopunctatus (Fabricius, 1787)
Description: A moderately large (9-13mm) bronze-black, predatory ground beetle living under decaying tree bark in woodlands. Very localised in Ireland but common where it occurs.
World Distribution: A Eurasian Boreo-temperate species (55), found across the whole of Europe, except southern Spain and Italy, to Siberia and Japan.
Irish Status: Of very restricted distribution in Ireland, with sites in Cork and Waterford as well as in north-east Antrim (Johnson & Halbert, 1902), but for nowhere in between. The Antrim populations may have had a Scottish origin, as the Mull of Kintyre is only 18km distant and the species is extant there (Luff, 1998). In the British Isles generally, this species has a curiously patchy distribution.
Ecology: Confined to woodland in its Antrim localities, mainly native hazel scrub or planted 19th-century mixed woodland. Occurs in cavities of red-rotted fallen timber (including conifers), or under stones in dryish woodland edge habitats. On the Continent, it is recorded about equally in deciduous and coniferous forest. Day et al. (1993) pitfall-trapped this species from both native oakwood and planted Sitka spruce at Breen Wood, Antrim.
Remarks: Den Boer et al. (1993) suggest that populations possessing greater numbers of elytral foveae (high pitters) occur more frequently in wet localities than populations possessing lower numbers (low pitters), and that the latter are correspondingly commoner in dry localities. All Irish specimens so far examined possess four or five foveae and so classify as low pitters. This does not sit well with Den Boer's hypothesis as Irish soils are wet by Continental standards, although the Antrim sites are comparatively well drained in an Irish context.