Taxonomy
Platycheirus perpallidus
Distribution
Species Biology
Preferred environment
Wetland/freshwater; water-margin tall sedge and reed beds in fen and transition mire and along rivers or the edge of lakes. In Ireland this insect occurs among tall, emergent vegetation, standing in the water at the edge of pools and lakes, or on scraw in fen, transition mire and flushes in blanket bog. It is a pronouncedly anthropophobic species, absent from the standard farming landscape of green fields plus hedges and from conifer plantations, parks and gardens. However, it can occur in abundance in Ireland in association with (and has been bred from) Carex riparia beds in constructed wetlands, introduced to farmland for treatment of livestock waste.
Adult habitat & habits
Flies among taller waterside vegetation or among emergent vegetation over water and among taller vegetation on scraw; as easily detected by use of a sweep net as by direct observation, but often to a significant extent inaccessible, due to the danger of approaching sufficiently close to its preferred haunts.
Flight period
Beginning April/beginning September, but almost no records for July. Larva: aphidophagous; described and figured by Maibach and Goeldlin (1991a); occurs on water's edge plants such as Typha and Carex rostrata; overwinters on the lower parts of its plant host under water and may even be found beneath ice (A. Maibach, pers. comm.) when the surface water freezes.
Flowers visited
Rubus chamaemorus (Nielsen, 1998); Cyperaceae; Juncus, Salix repens.
Irish reference specimens
In the collections of NMI and UM
Determination
Speight and Goeldlin (1990), Haarto and Kerppola (2007a), Bartsch et al (2009a). The adult insect is illustrated in colour by Stubbs and Falk (1983), Torp (1994) and Bartsch et al (2009a). In the male, this species is almost indistinguishable from P. immarginatus. It can exhibit a row of five or six, long bristly (black, or yellowish, or some of each) hairs, postero-dorsally, on the front femora, as in P. immarginatus. But, in P. perpallidus these bristly hairs each have a diameter distinctly less than the basal width of the clump of tangled white hairs that occurs at the base of the femur, posterodorsally. In P. immarginatus each of the long, black, bristly hairs present on the postero-dorsal edge of the front femur has a diameter even greater than the basal width of that clump of tangled white hairs. The female of P. perpallidus is most easily distinguished from that of P. immarginatus in having an almost continuously pale lateral margin to the abdominal tergites (this may be darkened by post-mortem discolouration), whereas in P. immarginatus the lateral abdominal margin is almost continuously (and widely) black.
Distribution
World distribution(GBIF)
From Norway and Finland south to northern France; from Ireland eastwards through northern and central Europe into European parts of Russia and on through Siberia to the Pacific coast; in N America from Alaska to New Brunswick and south to Utah. In most other parts of the Atlantic seaboard from which it is recorded, it is regarded as threatened. It is also regarded as threatened in parts of central Europe. P. perpallidus has a wide range in Europe, from northern Norway to Spain. It occurs through northern Europe into Siberia and on to the Pacific and in N America. But nowhere in Europe does it appear to be a frequent species.
Irish distribution
Recorded as occurring in Ireland in Coe (1953), but at that time this species was confused with various others in the genus Platycheirus. The presence of this species in Ireland was confirmed by Speight and Goeldlin (1990). Most Irish records of this species are from the west and the midlands. It is not a frequent species here, but neither is it threatened at present.
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.