Taxonomy
Xanthogramma citrofasciatum
Distribution
Species Biology
Preferred environment
Open ground; usually well-drained, unimproved, calcareous/mesophilous grassland, from xeric grassland up to and including grassland in the montane zone. The requirement of this species for unimproved grassland, where large, stable ant colonies can develop, is manifest in Ireland as elsewhere. Scattered records from earlier this century indicate that X. citrofasciatum may once have been widely distributed in low altitude grassland in Ireland, at least away from ground liable to flooding. However, it is now more-or-less confined to low-lying limestone pavement grasslands, and is by no means frequent even there. It occurs where there is a more complete grass cover than is characteristic of much of the limestone pavement, which may well be due to its dependence on root-aphids as a larval food source. Elsewhere, recent records are from the secondary habitat provided by the banks of the Grand and Royal canals.
Adult habitat & habits
Flies low through grasses etc., often settles on the nest mounds of ants of the genus Lasius.
Flight period
May/June, with a second peak in August in southern Europe. Larva: features of the puparium are detailed by Speight (1990), who distinguishes the puparium of this species from that of X. pedissequum (Harris) and an account of the larval biology is provided by Holldobler (1929). Larvae live in the nests of Lasius species, where they predate aphids tended by the ants. Egg: Chandler (1968).
Flowers visited
Convolvulus, Euphorbia, Scabiosa, Taraxacum.
Irish reference specimens
In the collections of NMI and UM
Determination
See key provided in the StN Keys volume. X. citrofasciatum is illustrated in colour by Torp (1994) and Bartsch et al (2009a). It has been referred to in much recent literature as X. festivum (L).
Distribution
World distribution(GBIF)
From southern Norway south to Iberia; from Ireland eastwards through central and southern Europe into European Russia and the former Yugoslavia; the Caucasus; western Siberia. This species is noticeably in decline in parts of western Europe. Elsewhere, X. citrofasciatum would currently be regarded as either decreasing or threatened over much of its European range, though it cannot be regarded as generally threatened at European level.
Irish distribution
Recorded as occurring in Ireland in Coe (1953). Irish records of this species form a band across central Ireland from Dublin south to Kilkenny in the east and Clare to Limerick in the west. But away from the limestone karst region X. citrofasciatum has all but vanished, along with its usual habitat of unimproved grassland. The fact that parts of the canal banks can provide a facsimile of conditions under which it might occur more naturally serves at least to show that the species was once more generally distributed in Ireland. But whether canal banks can be relied upon to provide for the long term survival of X. citrofasciatum is less certain. What is clear is that reversion of existing areas of improved/ intensively-used grassland to low-intensity permanent pasture where large, stable ant colonies can develop, is extremely unlikely, so that opportunities for X. citrofasciatum to recolonise lost territory will be virtually non-existent in the short to medium term. Within the limestone karst region, the future of X. citrofasciatum is arguably less certain than that of either Cheilosia ahenea or Paragus constrictus, both of which occur where there is a lower percentage of ground cover than appears necessary for X. citrofasciatum. The association of X. citrofasciatum with ground more completely covered in vegetation, essentially grassland, results in its habitat being more susceptible to efforts at land improvement and thus eradication of X. citrofasciatum. If these various issues are considered together, in the context of how they influence the status of X. citrofasciatum in Ireland, it is difficult to conclude other than that it should be regarded as threatened here. Indeed, it might be expected that it will rapidly move into the endangered category.
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.