Taxonomy
Cheilosia ahenea
Distribution
Species Biology
Preferred environment
Open ground; permanent, unimproved grassland from throughout the montane zone up to nearly 2000m, in both calcareous and non-calcareous subalpine pasture, in central Europe. This species occurs in Ireland in low-lying parts of the karst limestone areas, where it is found mostly in open, sparsely-vegetated, unimproved permanent pasture on limestone pavement. It occurs also on the landward side of the calcium-rich machair dune systems on the west coast, again in low-lying, unimproved, permanent pasture. The only other situation in which C. ahenea has been found in Ireland is in association with outcropping limestone on the grazed shores of L Conn (Mayo). Potential plant hosts are discussed by Speight and Claussen (1987), but plants actually used as a food supply by the larvae remain unknown. The apparent linkage between calcareous sites and this syrphid in Ireland might well be due to the availability of only one appropriate foodplant here, since no such linkage is evident in the central Europe, where C. ahenea can also be found in non-calcareous, unimproved, montane grassland. In the Alps it occurs from the montane zone up into subalpine grassland. The link with unimproved, permanent pasture seems strong for this species everywhere and its plant hosts must be presumed susceptible to eradication by reseeding and fertilisation of grassland, and to practices of alternation of pasturage with crop production (and hence to cultivation of the soil).
Adult habitat & habits
Flies close to the ground; males hover at 1-5 metres; often settles on bare ground or stones, in the sun.
Flight period
May/July. Larva: undescribed.
Flowers visited
Antennaria, Dryas, Hieracium, Ranunculus, Taraxacum.
Irish reference specimens
In the collections of NMI and UM
Determination
See key to males of European Nigrocheilosia species in StN Keys volume; Speight and Claussen (1987); Barkalov and Ståhls, (1997), who figure the male terminalia.
Distribution
World distribution(GBIF)
Ireland, Islay (small island off west coast of Scotland), France (Vosges, Alps, Pyrenees), Germany, Czech Republic, Switzerland, Liechtenstein and Austria; also in northern Spain (Cordillera Cantabrica). C. ahenea has recently (Parker, 2001) been found in a calcareous dune system on an island (Islay) off the coast of western Scotland, and subsequently in a few other sites in Britain. It is not known in the low countries and Scandinavia. The closest known continental records are from c.1000m in the Vosges mountains in north-east France.
Irish distribution
Added to the Irish list by Speight (1978b) as C. laskai. The synonymy of this species was subsequently established by Speight and Claussen (1987). Additional Irish records have been published by Nelson (1988). It is known in Ireland only from limestone pavement and machair systems from Co. Clare to Co. Donegal. Where found, this species is often abundant, especially in low-lying parts of the Burren which have not been subject to "improvement", i.e. bulldozing of loose surface rock into heaps and reseeding of the exposed soil, or fertilisation. It does seem extremely sensitive to grassland improvement and is also absent from machairs that have been subject to overgrazing. These are presumably indirect effects, mediated by adverse impacts upon its larval host plant. It can be hypothesised that C. ahenea is a survivor of early post-glacial colonisation of Ireland by cool-climate species, a process which ceased with further climatic amelioration. It is not currently under threat here, but is liable to remain dependent for its survival on protection of its habitat from agricultural improvement, or any other use of land which involved application of fertiliser or vegetation change (including introduction of such facilities as golf courses).
Temporal change
Records submitted to Data Centre in 2024
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References
Publications
Speight, M. C. D. (2008) Database of Irish Syrphidae
(Diptera). Irish Wildlife Manuals, No. 36. National Parks and Wildlife Service.
Department of Environment, Heritage and Local Government, Dublin, Ireland.
Speight, M.C.D. (2014) Species accounts of European
Syrphidae (Diptera), 2014. Syrph the Net, the database of European Syrphidae,
vol. 78, 321 pp., Syrph the Net publications, Dublin.