Ground Beetles of Ireland
Pelophila borealis
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 © Roy Anderson |
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Pelophila borealis (Paykull, 1790)
Description: A moderate-sized (9-12.5mm) bronze-black ground beetle with prominent depressions and puncturations on the elytra (see also Blethisa multipunctata). Lives on silty, clayey soils at the margins of lakes and slow rivers. An Arctic species virtually unknown in Britain but widespread in north and west Ireland.
World Distribution: A circumpolar Arctic-montane species (16). In Europe mainly in northern Fennoscandia with outlying relict populations in the British Isles, a distribution which Lindroth (1985) described as 'Boreo-British'. In mainland Britain known only from an isolated site in Glen Affric, Inverness (MacGowan & Owen, 1993). Offshore it occurs in the Orkney Islands.
Irish Status: Widespread in the north and west, particularly Cos Down, Antrim, Sligo, Leitrim and Cavan. Scattered along the west coast from Donegal to Kerry but rare in the centre and east. A colony is recorded from Blessington in Wicklow. This is a high northern species which may be at some risk from the effects of climate warming. A colony at Inch Abbey on the River Quoile, Down is known to have died out recently, so some of the easterly localities may be vulnerable.
Ecology: Strongly hygrophilous with a preference for open muddy or silty lakeshores or where there is a mixture of open, preferably stony, ground and better vegetated areas. Probably an exclusively lowland riparian species here which is absent from heavily vegetated ecotopes such as interdrumlin fens, or from deep peat and altitudes above 200m. In Fennoscandia it occupies broadly similar habitats to those observed in Ireland (Lindroth, 1985) but in Alaska it has been observed in much more heavily vegetated flushes and peaty lakeshores in the tundra provinces (R. Anderson unpublished). This habitat is probably typical of its Siberian range also. Interestingly, the single Scottish mainland record is for a vegetated flush at 840m i.e. more typical of the high boreal populations, whereas the Orkney populations are mostly recorded from low-level stony lakeshores much as in Ireland (MacGowan & Owen, 1993).
Remarks: Irish populations show little morphological variation and the dorsum has a relatively uniform brassy lustre. This contrasts with populations in Fennoscandia (Lindroth, 1985), Alaska and Canada (Lindroth, 1963) where there is more variation and rufinistic forms occur widely.