Tachydromia fuscinervis (Frey)

Shamshev, Igor V. & Grootaert, Patrick, 2024, Revision of the described Nearctic species of the genus Tachydromia Meigen (Diptera: Hybotidae), Zootaxa 5403 (2), pp. 151-196 : 166-168

Tachydromia fuscinervis (Frey)

( Fig. 7 )

Tachista fuscinervis Frey, 1915: 3 and 15 (♀). Type locality: Russia, Yakutia , Kharaulakhskiy Ridge near mouth of the Lena River [~ 71°44′N 128°16′E].

Tachydromia fuscinervis : Chvála, 1970: 430 (♀); Shamshev, 1994a: 33, fig. 1 (♂; type material).

Material examined: NORTH AMERICA. CANADA. British Columbia: Summit Lake, mi 392 Alaska Hwy. , 4500’, 1.vii.1959, R. E. Leech (1 ♀, CNC) ; same locality, 4500’, 2–4.vii.1959, R. E. Leech (2 ♂, 11 ♀, CNC) ; same locality, 5000’, 6.vii.1959, R. E. Leech (4 ♀, CNC) ; same locality, 5000’, 6.vii.1959, E.E. MacDougall (1 ♂, 3 ♀, CNC) ; same locality, 4500’, 8.vii.1959, R. E. Leech (1 ♀, CNC) ; same locality, 4500’, 8.vii.1959, E.E. MacDougall (2 ♀, CNC) ; same locality, 4500’, 11–14.vii.1959, E.E. MacDougall (2 ♀, CNC) ; same locality, 4500’, 17–19.vii.1959, R. E. Leech (11 ♀, CNC) ; same locality, 4200’, 21.vii.1959, R. E. Leech (4 ♀, CNC) ; same locality, 4500’, 23–24.vi.1959, E.E. MacDougall (1 ♂, 1 ♀, CNC) . Manitoba: Churchill , 12.vii.1952, J.G. Chillcott (1 ♂, 2 ♀, CNC) ; Warkworth Cr., nr. Churchill , 21.vi.1952, J.G. Chillcott (1 ♀, CNC) ; same locality, 7.vii.1952, J.G. Chillcott (1 ♀, CNC) ; Fort Churchill , 26.vi.1952, J.G. Chillcott (1 ♂, 1 ♀, CNC) ; Farnsworth L., nr. Churchill , 26.vi.1952, J.G. Chillcott (1 ♀, CNC) ; same locality, 22.vii.1952, J.G. Chillcott (1 ♀, CNC) ; Mile 504, Hudson Bay Ry., 21.vi.1952, J.G. Chillcott (1 ♀, CNC) ; Mile 505, Hudson Bay Ry., 7.vii.1952, J.G. Chillcott (1 ♀, CNC) ; same locality, 16.vii.1952, J.G. Chillcott (1 ♀, CNC) . Yukon: North Fork Crossing, mi. 43 Peel Plt. Rd. , 3500’, 24.vi.1962, R. E. Leech (2 ♀, CNC) ; North Fork Crossing, mi. 42 Peel Plt. Rd. , 3500’, 25.vi.1962, R. E. Leech (1 ♂, 2 ♀, CNC) ; same locality, 26.vi.1962, P.J. Skitsko (1 ♂, 4 ♀, CNC) ; same locality, on Salix , 26.vi.1962, R. E. Leech (2 ♂, 4 ♀, CNC) ; North Fork Crossing, mi. 43 Peel Plt. Rd. , 3500’, on Salix , 26.vi.1962, R. E. Leech (1 ♀, CNC) ; North Fork Crossing, Ogilvie Mts. 3.vii.1962, P.J. Skitsko (1 ♀, CNC) ; same locality, 7.vii.1962, P.J. Skitsko (1 ♀, CNC) ; North Fork Crossing, mi. 43 Peel Plt. Rd. , 3500’, 3.vii.1962, P.J. Skitsko (1 ♀, CNC) ; same locality, 4.vii.1962, P.J. Skitsko (1 ♂, CNC) ; same locality, 3500’, 3.vii.1962, P.J. Skitsko (3 ♀, CNC) ; same locality, 4.vii.1962, R. E. Leech (2 ♀, CNC) ; same locality, 3.vii.1962, R. E. Leech (1 ♀, CNC) ; same locality, on Salix , 6.vii.1962, R. E. Leech (6 ♀, CNC) ; Caribou Bar Creek , 19.vi.1972, FWI-Pipeline Project (1 ♂, CNC) ; Dempster Hwy. km 135–145, spruce-willow forest, 14.vi.1984, S. & J. Peck (2 ♂, 5 ♀, CNC) . USA. Alaska: Umiat , 3.vii.1959, R. Madge (2 ♀, CNC) ; same locality, 7.vii.1959, R. Madge (1 ♂, 2 ♀, CNC) ; same locality, 13.vii.1959, R. Madge (1 ♀, CNC) ; same locality, 13.vii.1959, R. Madge (1 ♂ (dissected), 2 ♀, CNC) ; same locality, 14.vii.1959, R. Madge (1 ♂, 6 ♀, CNC) ; Cape Thompson , 29.vii.1961, R. Madge (1 ♀, CNC) ; same locality, 25.vii.1961, R. Madge (1 ♀, CNC) ; Isabel Pass, mi. 206 Richardson Hwy. , 2900’, 13.vii.1962, P.J. Skitsko (1 ♂, 3 ♀, CNC) ; same locality, 17.vii.1962, P.J. Skitsko (1 ♂, 2 ♀, CNC) ; same locality, 18.vii.1962, P.J. Skitsko (1 ♀, CNC) ; same locality, 18.vii.1962, P.J. Skitsko (1 ♀, CNC) ; same locality, 19.vii.1962, R. E. Leech (1 ♂, CNC) ; Mt. Fairplay , mi. 32 Taylor Hwy., 3600 ’, 11.vii.1962, R. E. Leech (1 ♀, CNC). EURASIA. RUSSIA. Buryatia Republic: env. Mondy, Sayany Mountains , 2100 m , 20.vii.1965, Gorodkov (1 ♂, ZISP). Chukotka Autonomous Okrug: Markovo , 21.viii.1966, Gorodkov (2 ♀, ZISP). Krasnoyarskiy Territory: Taymyr, Tareya , slopes of river shore , 26.vii.1967, Gorodkov (5 ♂, 9 ♀, ZISP) .

Diagnosis. The species is distinguished by the following combination of characters: wing membrane without bands, mostly faintly infuscate, brownish clouded along veins; palpus yellow; proepisternum pruinose; legs almost entirely yellow, tarsomeres brown annulated, male mid femur with excavation close to base.

Redescription. Male ( Fig. 7A ). Length: body 2.1–2.3 mm, wing 2.2–2.3 mm. Head black, mostly with pale setation. Occiput extensively greyish pruinose, broadly shiny along eyes laterally; 2 moderately long brownish vertical setae, some thin setae of different lengths around neck and near mouth-opening; row of minute postoculars; vertex varying from shiny to faintly pruinose. Ocellar triangle faintly pruinose, 2 short ocellars. Frons usually narrowly shiny medially otherwise pruinose but sometimes entirely pruinose or largely shiny; slightly broadened towards ocellar triangle, rather narrow, above antennae 2.0–2.5 times as broad as anterior ocellus. Antenna with scape and pedicel yellow, postpedicel brownish to yellowish brown (sometimes paler at base), stylus brown. Postpedicel rather egg-shaped; stylus subapical, nearly 2.0 times as long as pedicel and postpedicel combined. Proboscis blackish brown. Palpus unmodified, yellow, elongate oval, slightly shorter than proboscis, faintly whitish pubescent, with scattered pale setulae, bearing 1 black, short subapical seta (shorter than palpus).

Thorax entirely black, largely shiny; prothoracic sclerites (except postpronotal lobe), anepisternum narrowly anteriorly and meron marginally densely whitish grey tomentose, notopleural depression, scutellum and postnotum faintly greyish tomentose. Postpronotal lobe large, elongate oval, lacking conspicuous setae, with scattered minute setulae. Mesonotum with 1 long notopleural, 1 short postalar and 4 scutellars (apical pair long, lateral pair somewhat shorter); some minute setulae present behind postpronotal lobe and on notopleural depression anteriorly; acrostichals lacking; dorsocentrals uniserial, scattered, mostly minute, 1 prescutellar pair long (nearly as long as apical scutellars).

Leg colour: almost entirely yellow; mid and hind coxae brownish; femora on about middle (especially hind femur) and tibiae at apex often somewhat darker, rather brownish yellow; tarsomeres of all legs brown annulated (more distinctly on fore and mid legs; basitarsi of all legs and hind tarsomere 2 narrowly brown at apex, remaining tarsomeres mostly brown, tarsomere 5 almost entirely brown). Fore coxa clothed in numerous pale setae and silvery tomentose anteriorly; bearing black, spine-like, anteroventral subapical seta.Fore femur thickened, whitish pubescent ventrally, with rows of anteroventral and posteroventral pale minute setae longer closer to base; 2 long fine setae near extreme base. Fore tibia spindle-shaped, with unmodified setation. Mid femur somewhat thickened, faintly pubescent on apical part ventrally; deep excavation closer to base, basal margin of excavation pointed; bearing 1 short brownish to brownish yellow spine-like seta near base, 1 short and 1 longer, black curved spine-like setae before excavation, 1 moderately long strong black seta just beyond excavation and rows of black anteroventral and posteroventral spinule-like setae. Mid tibia somewhat constricted on subapical part ventrally, with short flattened apical projection, bearing ventral, black spinule-like setulae disappearing before subapical constriction. Hind femur unmodified, with rather short anteroventral setae. Hind tibia and tarsus unmodified.

Wing usually normally developed (sometimes somewhat shortened), rounded at apex, with unmodified venation; faintly brownish infuscate along longitudinal veins (usually less distinct along M 1). One short basal costal seta present. Vein R 2+3 straight. Veins R 4+5 and M 1 parallel throughout, close to each other. Crossveins r-m and bm-m broadly separated. Calypter brownish, with brownish yellow fringe. Halter uniformly yellow.

Abdomen brown to blackish brown, shiny; tergites mostly with scattered minute setulae, sternites covered with numerous setulae; pregenital segments unmodified (except segment 8), with long posteromarginal setae.

Hypopygium ( Fig. 7B–D ) blackish brown, moderately large, elongate oval. Right epandrial lamella ( Fig. 7C ) rather subglobular viewed laterally, bearing about 10 unmodified long setae apically; ventral projection bearing 10–11 long, flattened setae. Right surstylus separated from epandrial lamella, long, narrow, with 3 spine-like setae closer to base and short, simple setae at apex. Left epandrial lamella ( Fig. 7D ) small, with 3 moderately long setae apically. Left surstylus not separated from epandrial lobe, elongate, rounded apically, with numerous long setae. Cerci ( Fig. 7B ) separated, with some unmodified moderately long setae; right cercus digitiform, narrow; left cercus somewhat shorter and broader than right cercus. Hypoproct not produced beyond apices of cerci.

Female. Fore coxa with thin, yellowish, subapical seta ventrally. Mid femur unmodified, with rows of anteroventral and posteroventral short brown setae ending by 2 longer pale setae near base. Mid tibia lacking apical projection, slender throughout. Otherwise as in male. Abdominal segment 6 shiny, visible parts of segments 7–8 pollinose. Cercus brownish, long, slender, with minute setulae.

Remarks. Tachydromia fuscinervis belongs to the T. fuscinervis group of species ( Shamshev & Grootaert 2018). There is a very similar species to T. fuscinervis , a little-known Eurasian species that may be found in the future from North America, namely T. microceroides Chvála (a new name for T. microcera (Frey)) ( Frey 1943; Chvála 1977, 1988). The male of this species remains undescribed, but we have examined many male specimens deposited in ZISP. In addition, the lectotype of T. microceroides was examined by I.S. in 2019 (MZH). Tachydromia microceroides is almost identical with T. fuscinervis differing by an extensively shiny occiput (only central area of occiput just above neck and below neck towards mouth-opening faintly grey pruinose). Both species have similar distribution in Eurasia.

Distribution. Holarctic. North America (first record): Canada (British Columbia, Manitoba, Yukon), USA (Alaska). Eurasia: Russia (Western and Eastern Siberia, Far East).

Figures

FIGURE 7. Tachydromia fuscinervis (Frey), male (USA, Alaska; CNC). A. Habitus, lateral view. B. Hypopygium, dorsal view. C. Right epandrial lamella, right surstylus and right cercus, lateral view. D. Left epandrial lamella and left surstylus, lateral view. Abbreviations: cerc—cercus; lft sur—left surstylus; rt cerc—right cercus; rt sur—right surstylus. B–D: scale bar is 0.1 mm.