Taxonomy
Criorhina ranunculi
Distribution
Species Biology
Preferred environment
Deciduous forest; Betula, Fagus and Quercus forest with overmature trees. Although this species is known to be associated with all of the above trees indigenous to Ireland, C. ranunculi is demonstrably associated with overmature birch here, and if this hoverfly does use other trees in Ireland, this is not apparent. However, existing records are from localities where birch occurs within mature woodland, intermixed with other trees, not from stands of birch occurring in isolation.
Adult habitat & habits
Primarily arboreal, but descends to visit flowering shrubs in sun-lit glades and can be found investigating patches of wet, trunk-base rot (frequently in the shade) or, in the case of the males, hovering adjacent to patches of wet trunk-base rot; flies extremely fast, with a characteristic, highpitched whine, often zig-zagging between the branches of flowering trees.
Flight period
Beginning of March/mid May and on to end June at higher altitudes. Larva: described and figured by Rotheray (1991), from larvae from a stump of Fagus; almost certainly occurs in trunk-base, fungus-infested, wet-rot cavities, of Betula, Fagus, Quercus and Ulmus.
Flowers visited
Cardamine pratensis, Cornus sanguinea, Crataegus, Photinia, Prunus cerasus, P. spinosa, Rubus, male Salix, Sorbus aucuparia.
Irish reference specimens
In the collections of UM
Determination
van der Goot (1981). See Key provided in StN Keys volume. The more usual colour form of the adult insect is illustrated in colour by Bartsch et al (2009b), Colyer and Hammond (1951) and Stubbs and Falk (1983). The variety ruficauda (Meigen) is entirely rufous-haired and has been mistaken for C. pachymera (Egger) by some authors, notably Seguy (1961).
Distribution
World distribution(GBIF)
Southern Norway and southern Sweden south to central Spain; from Ireland eastwards through central Europe into European parts of Russia.
Irish distribution
Added to the Irish list by Nash and Speight (1976). There are but four Irish records of this insect and it has to be regarded as threatened here. C. ranunculi would be a candidate for inclusion of any Irish list of insects requiring protection. It is also regarded as threatened in other parts of Europe's Atlantic seaboard, and in both Germany and Switzerland. C. ranunculi is endemic to Europe.
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.