Ground Beetles of Ireland

The Irish Fauna - Carabidae of Ireland

The Carabidae or ground beetles are a world-wide assemblage of upwards of 30,000 species. These are often referred to colloquially as black beetles or clocks. The European fauna is relatively rich but the principal centres of diversity are in the south and east in areas such as the Balkans which have escaped the full rigours of the last glaciation. There is evidence with respect to several groups of invertebrates that re-investment of pre-Glacial ranges in Europe is an ongoing process and that all the available niches in the north and west, particularly in Britain and Ireland, are by no means filled.

Ireland and Britain were separated from Europe early in the Postglacial era. In the case of Ireland land bridges to Britain were only open for about 1500 years. The fauna is therefore impoverished even by British standards. The fauna of Ireland further suffers by being further off the European mainland, by the intense oceanicity of its climate, and by the relatively smaller land area and suite of habitats. Despite this, the Irish Carabidae in numbers of species (211) represents 61% of the British total (347) and several species found in Ireland do not occur in Britain. Examples include Bembidion argenteolum which was fairly widespread on Lough Neagh at the turn of the century, and Agonum lugens recently discovered in Co. Clare. Both species are found in Scandinavia and could have been more widespread in the British Isles early in the Postglacial period but have since died out. Other species representative of the Boreal or cold phase of Postglacial time, are more widespread in Ireland than Britain e.g. Dyschirius obscurus and Pelophila borealis. The former is still widespread on Lough Neagh but is only known as a late immigrant in south-east Britain, while the latter is generally distributed in north and west Ireland but has only a single locality on mainland Britain.

There are therefore some strengths to play to in the fauna. The ecological groups best represented are the hygrophilous (moisture-loving) swamp and inundation species (Agonum, Badister), cold-adapted species (Pelophila, some Bembidion) and peatland types (Carabus nitens, C. clatratus). Species requiring warmth for development tend to be poorly represented in Ireland, except for those with specific adaptations such as the Lough Neagh sandy beach fauna. This latter group makes use of the heat-retentive properties of fine, moist sand for development and feeding and is confined to bare, wet sand of a particular particle size. Some marine riparian faunas also depend on beach sands for these properties and on Lough Neagh there is an overlap between purely freshwater and marine littoral faunas. Bembidion pallidipenne, for instance, occurs both on Lough Neagh and on sandy coasts where it is a diurnal feeder. The largely nocturnal Amara fulva is an insect of loose fine sand above the strandline on marine beaches. On Lough Neagh it occupies a similar niche between the wave-washed damp sand of the shoreline and fenny or swampy ground behind. In comparison to lake and coastal faunas, riverine riparian faunas are relatively poorly known in our area. Such information as is available suggests that arterial drainage schemes have devastated large areas and that faunas are now disjunct and scattered. Irish rivers anyway have a limited range of riparian habitats of which fine gravel or sand banks are particularly localised. These support a diverse and interesting fauna in northern Britain and an attempt should be made in future to identify remaining important sites in Ireland.

With the specific exception of river margin faunas, the more fussy hygrophilous species are well represented in Ireland. Ireland has, for instance all of the British species and more than the Scandinavian total of Badister. The stenotopic (fussy) Badister spp. are mostly confined to the south and west and do not get further north than the midland counties. The wet-loving genus Agonum is also well represented and much more common over the totality of landscape than anywhere else in Europe. Strangely, two notable peatland Agonum are absent i.e. A. ericeti and A. sexpunctatum. We do have two notable peatland Carabus, however, C. clatratus and C. nitens, for both of which Ireland has very important European populations. Conservation of the Irish sites for these should be a priority. Carabus nitens has disappeared from much of lowland northern Europe and attempts have been made to re-introduce it to peatlands in Holland and in the north German plain but with very mixed results. Peatlands also represent important habitats for most of the other Irish Carabus such as C. glabratus, C. arvensis and C. problematicus. On a few of the best sites all of the Irish Carabus can be taken from the same small area. Lowland raised bogs, a very threatened habitat in Ireland, strangely do not appear to possess a unique or interesting carabid fauna. Cutover bogs, especially those with resurgent fen floras, tend to have more diverse faunas. Hill peat, especially where mires or pool complexes occur, also usually have interesting species.

The summits of mountains in Ireland support a mixture of species, some governed by the need for the better-drained conditions found on summit moraine and which are often also found in sandy places at lower altitudes, others for low temperatures and exposure in keeping with an Arctic or montane distribution elsewhere. The high mountain fauna of Ireland is, however, still poorly known, particularly in the west and north. The recent discovery of Miscodera arctica in both Down and Antrim, of Notiophilus aestuans in Down, plus the staphylinid Stenus glacialis in several Irish mountain districts, illustrates this point. In the context of global warming, a more determined attempt to evaluate the fauna and its need for conservation, is required.

There is good evidence that a long historical record of human interference in the landscape has caused some adaptation within carabid faunas, a process that continues today. McFerran et al. (1995) have indicated that unimproved hay meadows and lakeshore pasture in Fermanagh is now an important habitat for Carabus clatratus, previously thought to be confined to wet, undisturbed peatlands. Is this also the case elsewhere? Points like this can only be clarified and re-inforced by amateur involvement in recording. There is little point in formulating conservation strategies about groups such as ground beetles when the evidence for their status and preferences is so obviously lacking.