Platycheirus nielseni Vockeroth, 1990

Prokhorov, A. V., Popov, G. V. & Zaika, M. I., 2018, New Records Of Hoverflies (Diptera, Syrphidae) From Ukraine. Iii. Pipizinae And Syrphinae, Vestnik Zoologii 52 (3), pp. 241-250 : 243-244

Platycheirus nielseni Vockeroth, 1990 (figs 7–10)

M a t e r i a l e x a m i n e d. Ukraine. Zakarpattia Region : Synevyr Lake, 48.62 N 23.67 E, 15.06.2005 , 1 Ơ

(collector unknown).

D i s t r i b u t i o n: from Fennoscandia south to northern France; from Ireland eastwards through northern and central Europe (including northern Italy), frequent in the central Alps; Hungary to European Territory of Russia; Siberia and Far East of Russia (Magadan Region, Khabarovsk Region); scattered records from Nothern America from Alaska through much of Canada and south through the Rocky Mountains to Colorado ( Mutin & Barkalov, 1999; Tóth, 2011; Speight, 2017); Ukraine (first record).

Diagnosis. This species belongs to P. peltatus group ( Young et al., 2016); it is very similar to P. amplus Curran, 1927 ( Vockeroth, 1990; Young et al., 2016) in having first tarsomere of fore leg with weak dorsal keel on apical half, but without distinct keel on basal half. Male can be distinguished from P. amplus by the mid tibia with apex strongly swollen (fig. 10) (in P. amplus , the apex of the mid tibia weakly swollen); the “apical half of ventral surface of the mid tibia with suberect, tangled, dark pile, which is approximately equal in length to tibial diameter” (fig. 10) (in P. amplus , the “apical half of ventral surface of the mid tibia with very short, scarcely discernible pile”); the anepimeron with pile only on upper half, and pile forming a compact tuft (in P. amplus , the anepimeron with at least some pile on lower half, and pile on upper half not forming a compact tuft); the wing membrane entirely trichose (in P. amplus , bare area of the cell bm at most one-third as long as the cell and well separated from anterior margin ( Young et al., 2016). From similar P. peltatus (Meigen, 1822) (figs 11–14) it differs by the strongly swollen apex of the mid tibia with a tuft of long hairs at the base of dilation, the hairs pointing towards the base of the tibia (fig. 10) (in P. peltatus , the mid tibia only slightly swollen with a tuft of short erect hairs, as on fig. 14), the wing with the basal cell bm without distinct bare area, sometimes with “very small bare areas at bases of cells c and bm” (in P. peltatus , the cell bm with medial bare area in the basal half) ( Vockeroth, 1990; Bartsh et al., 2009; Van Veen, 2010; Young et al., 2016).

Note. In P. nielseni male, the scutum is described as “with hairs mostly black” ( Vockeroth, 1990) or “with mixed black and yellow pile” ( Young et al., 2016). In the Ukrainian specimen the scutal hairs are mostly pale.