(Figs 77–80)
Tachypeza sericeipalpis Frey in Lundström & Frey, 1913: 10. Type locality: Cape Mikulkin (Kanin Peninsula, 67°48′N 46°41′E), Nenets Autonomous Okrug, Russia. Other references: Frey, 1915: 14 (faunistic survey); Chvála, 1975: 224 (revision); Shamshev, 2016: 148 (checklist).
Tachypeza dilutata Frey, 1915: 14 (as var. of sericeipalpis Frey). Type locality: Kharaulakhskij Ridge near mouth of the Lena River (~ 71°44′N 128°16′E), Yakutia, Russia.
Material examined. CANADA. Northwest Territories: Ford Lake, 63°11′N 107°19′W, 23.vi.1966, G.E. Shewell (1 ♂, 1 ♀, CNC). Nunavut: Whatever Lake, 62°41′N 97°03′W, vii.1989, pitfall trap, J. Pilny (3 ♂, 1 ♀, CNC). RUSSIA. Chukotka AO (Wrangel Island): N Somnitelnaya Bay, 27.vii.1966, KBG (1 ♀, ZIN); northern slope of Berry Peak, 7 km ESE Sovetskaya Mtn, 350 m, on stones, 12.vii.1972, KBG (5 ♂, 6 ♀, ZIN).
Recognition. Small blackish flies (body 2.5–3 mm) (Fig. 72); palpus pale to pale yellow, whitish pubescent, with short pale hair-like setae (sometimes 1 subapical seta brownish); prothoracic sclerites (except postpronotal lobe) densely silvery grey tomentose, mesopleuron almost entirely shiny, 1 strong npl, 2 broadly set similar sctl, 1 (sometimes 2) strong prescutellar dc; legs almost uniformly brown; halter with yellow knob. Male: mid femur with row of 6–7 closely set black short anteroventral spine-like setae on about basal 1/3 and 2 closely set, moderately long, spine-like setae near extreme base; mid tibia with shallow, ventral subapical excision. Male terminalia (Figs 78–80) large, brown, epandrium shiny. Cerci (Fig. 79) separated, shifted to inner margin of right epandrial lamella; right cercus digitiform, short, with apex slightly extended beyond apex of right epandrial lamella, covered with short setae stronger on inner margin; left cercus short, broad, subrectangular; with some short setae. Hypoproct weakly sclerotized, rather subtriangular, separated from both cerci, bare. Right epandrial lamella (Fig. 78) without ventral lobe, produced apicoventrally; with cluster of several spine-like short marginal setae apically; right surstylus separated from epandrial lamella, narrow, with two projections, outer projection very short, inner projection long, stylet-like; right bacilliform sclerite with 2 closely set spine-like setae. Left epandrial lamella narrow; with large apodeme; bearing some setulae apically; left surstylus (Fig. 80) large, rather subtriangular (lateral view) but with additional narrow pointed projection dorsally; with short marginal setae apically. Hypandrium hump-backed.
Distribution. Holarctic; T. sericeipalpis has a disjunct distribution occurring in Eurasia across the arctic region of Russia from Murmanskaya Province to Chukotka (including Wrangel Island) and is found locally in mountains of Altay Republic and Buryatia (Shamshev, unpubl. data). In North America, this species is newly recorded from the Northwest Territories and Nunavut of Canada.
Remarks. The male terminalia of this species are here illustrated for the first time.