Wetland/forest; Alnus/Salix carr and poorly drained scrub (Prunus spinosa) woodland. The sort of poorly-drained Salix woodland and poorly-drained, scrub-invaded, unimproved pasture frequented by this species in Ireland is extremely scarce over most of western Europe, where C. nebulosa is correspondingly scarce. In central Europe it is primarily a montane to sub-alpine species. Whatever the larval host plant may be it is evidently not able to survive modern farming practice, to judge from the total absence of C. nebulosa from all forms of improved farmland. Similarly, C. nebulosa is absent from managed woodland and conifer plantations, except in a few cases where attempts at site drainage have failed. It has to be regarded as a markedly anthropophobic syrphid in Ireland.
Adult habitat & habits
Clearings and tracksides; males hover up to 7m along tracks and paths, beside Salix or Crataegus in flower, descending to settle on low-growing plants whenever the sun disappears behind a cloud; females fly low over ground vegetation, settling to rest in the sun on dead grasses (e.g. Molinia tussocks) and both sexes visit flowers of trees.
End April/beginning June, and on to the beginning of July at higher altitudes. Larva: undescribed, but Doczkal (2002) reports egg-laying by this species on leaves of Centaurea nigra.
Crataegus, Prunus, male Salix, Taraxacum, Tussilago.
Irish reference specimens
In the collections of NMI and UM
van der Goot (1981). Until recently, specimens of this species with unmarked wings have also appeared in literature under the name langhofferi, Becker. Such specimens would be liable to misdetermination using the keys provided by van Veen (2004). The male terminalia are figured by Claussen and Speight (1988a). The adult insect is illustrated in colour by Stubbs and Falk (1983).
Finland south to northern France; from Ireland eastwards through central Europe to Bulgaria and European parts of Russia.
Records submitted to Data Centre in 2021
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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.