Genus Sympycnus Loew, 1857

Type-species: Porphyrops annulipes Meigen, 1824 [= Sympycnus pulicarius (Fallén, 1823)] (designation by Coquillett 1910).

Diagnosis. There are no known synapomorphies characterising Sympycnus as a whole. As such, the genus is recognized by the absence of characters which define the other sympycnine genera (Grichanov & Brooks 2017, in press). The Palaearctic species are usually small, bearing the following combination of characters (Grichanov et al. 2011): antennal scape bare; distal inner margin of pedicel straight; acrostichals distinct, even though sometimes small; usually six, rarely 5 pairs of strong dorsocentral bristles; metepimeron without hairs; mesonotum without black or brown lateral spots; segments of fore tarsus usually simple or shortened, rarely ornamented with remarkable hairs; hind tarsus with tarsomeres 1 and 2 not shortened; male hind basitarsus rarely ornamented with remarkable setae or hairs; male hind tarsomere 2 never having worm-like process; male hind tarsomere 3 usually shorter than tarsomere 2, often bearing one or more modified setae; tarsomere 4 often longer and thinner than tarsomere 3, sometimes polished; male surstyli usually reduced and fused with each other, being also fused at base with epandrium; epandrial lobe usually broad, projected; female face usually narrow with clypeus rarely bulging (e.g. S. simplicipes Becker, 1908).