Taxonomy

Anasimyia transfuga

Distribution

Species Biology

Preferred environment

Wetland; margins of mesotrophic pools and lakes with Scirpus or Sparganium. Unlike its close relative A.contracta, A.transfuga exhibits no clear association with Typha. The available records are from shallow standing water with marginal vegetation of Phragmites or Scirpus, on both unmodified (lake edge) and modified (ornamental pond, standing water ditch edging valley bog and pool in cutover bog) sites. Due to confusion with A.contracta, information pertaining to "A.transfuga" published from prior to 1980 has to be discarded, including that in Speight et al (1975).

Adult habitat & habits

Flies among water-margin vegetation, settling on emergent stems etc., often where the water is up to 1m. deep.

Flight period

Early May/July, with some 9 records into August. Larva: not distinguished from that of A.contracta, but see Hartley (1961).

Flowers visited

White umbellifers, Caltha palustris, Ranunculus repens, Sonchus arvensis, Sorbus aucuparia, Taraxacum.

Irish reference specimens

In the collections of NMI and UM

Determination

Extremely similar to A.contracta, with which it has been confused until recently. These two species may be found on the wing together. See Key provided in StN Keys volume. A.transfuga can be distinguished by means of the keys in Bartsch et al (2009b), Claussen and Torp (1980), Speight (1981), van der Goot (1981b) and Verlinden (1991). The male terminalia are figured in Claussen & Torp (1980), Torp (1984) and van der Goot (1981). The adult insect is figured in colour in Bartsch et al (2009b), Stubbs and Falk (1983), Torp (1984, 1994) and van der Goot (1986).

Distribution

World distribution(GBIF)

Southern Sweden south to northern France (Paris basin); Ireland east through mountainous parts of central and southern Europe (the former Yugoslavia, Roumania) into Russia as far as southern parts of central Siberia (Tuva). 

Irish distribution

Recorded as occurring in Ireland in Coe (1953), but at that point in time this species was confused with A.contracta. The presence of A.transfuga in Ireland was confirmed by Speight (1981a). Earlier records of A.transfuga in Ireland (e.g. in Speight et al, 1975) comprise a mixture of A.contracta and A.transfuga records, and cannot be relied upon. Since 1981, additional Irish records have been published by Anderson (1988) and Nelson (1988). However, there are few Irish records of this species and it is probably less frequent in Ireland than in any other country of the Atlantic seabord of Europe, from Denmark to northern France (inclusive). Why this is so is unclear. Suffice it to say that, to err on the side of caution, A.transfuga should probably be regarded as threatened in Ireland.

Temporal change

Records submitted to Data Centre in 2021

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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.

Images