Taxonomy
Cheilosia semifasciata
Distribution
Species Biology
Preferred environment
Open ground/forest; stabilised scree slopes, cliffs and rock outcrops in sheltered locations up to 2000m, or within woodland at altitudes up to and including those of Alnus viridis scrub; dry-stone walls; also poorly-drained deciduous forest. This species can also occur in urban situations (Barkemeyer, 1997). Schmid (2004b) noted frequent occurrence of C.semifasciata in suburban gardens in SW Germany, using Sedum telephium as larval host, observing that the larvae could even be found in Sedum on traffic islands in the roads and in seedlings on sale in garden supply shops. He concluded the species was self-maintaining in the urban environment there. In continental Europe this species occurs in at least three very different habitats: humid oak/hornbeam forest, subalpine grassland and old walls/ cliffs. And it also reaches very high population densities along the edges of the cycle tracks in the leafy suburbs of towns and cities in central Germany! In its suburban existence, C.semifasciata makes use of Sedum as a larval foodplant, a plant which it also inhabits in the subalpine zone. On old walls and cliffs it uses Sedum or Umbilicus. Its plant host in deciduous forest is uncertain. Wherever this species is found in Ireland, close inspection of the site nearly always reveals the presence of either Sedum or Umbilicus in the immediate vicinity of the adult flies. The rare exceptions involve the fly occurring with large stands of Allium ursinum. The use of Umbilicus as a larval foodplant is well-established, but no clear association has been demonstrated with Allium. Another continental European Cheilosia species, C.fasciata, is a leaf miner of Allium ursinum, so there is some possibility that C.semifasciata might, on occasion, exploit the same plant. However, no direct observations of this exploitation has yet been obtained. If C.semifasciata larvae were using A.ursinum, evidence of leaf/stem mining would be expected. The most widely distributed habitat for Umbilicus in Ireland is old stone walls and C.semifasciata may be found in association with the plant in such situations, though the plant host is clearly more frequent than the fly. Where Umbilicus occurs on cliffs and scree slopes the fly may also be found, but normally only in sheltered spots.
Adult habitat & habits
Flies low over ground vegetation and rock, settling on foliage or rock in the sun; males hover up to 3m in woodland glades or sheltered hollows in rocky terrain. The male flies seldom hover far from stands of the larval foodplant and are often no more than a few metres from it.
Flight period
End March/end May. Larva: described and figured by Rotheray (1988c) and illustrated in colour by Rotheray (1994); a miner in the leaves of Saxifraga, Sedum and Umbilicus (Hering, 1957). This species overwinters as a puparium.
Flowers visited
Alliaria petiolata, Allium ursinum, Anemone nemorosa, Prunus spinosa, Ranunculus, male Salix, Taraxacum, Vaccinium myrtillus.
Irish reference specimens
In the collections of NMI
Determination
Bradescu (1991), Haarto and Kerppola (2007a) and van der Goot (1981) may be used to separate C.semifasciata from related species apart from C.rhodiolae. To separate C.semifasciata and S.rhodiolae from one another it is necessary to refer to Schmid (2000). As Schmid (2000) says, high altitude specimens of C.semifasciata may have entirely black legs. This, together with the fact that the leg hairs on the mid tibiae in this high altitude form can also be all black, can make the species very difficult to distinguish from C.rhodiolae Schmid. The surstyli of the male terminalia are figured by Stubbs and Falk (2002). The male is figured in colour by Bartsch et al (2009b).
Distribution
World distribution(GBIF)
northern Norway and Finland south to northern France; from Ireland eastwards through mountainous parts of central Europe to Roumania and Bulgaria. It is endemic to Europe, but not to any one part of the continent, occurring widely but not frequently.
Irish distribution
Added to the Irish list by Speight et al (1975). The Irish records for this species are scattered round the island at low altitude and usually not far from the coast - though none are from coastal sites. The species is not frequent, but neither can it be regarded as under threat here.
Temporal change
Records submitted to Data Centre in 2024
The following map is interactive. If you would prefer to view it full screen then click here.
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.