Tachydromia bimaculata (Loew)

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 : 155-159

Tachydromia bimaculata (Loew)

( Figs 2 , 3 )

Phoneutisca bimaculata Loew, 1863: 19 [Cent. 3, no. 35]. Type locality: USA, Alaska, Sitka .

Tachydromia bimaculata : Melander, 1928: 280 (♂).

Notes on type series. Loew (1863) described Phoneutisca bimaculata from the female sex only based on an unspecified number of specimens taken by Finnish entomologist R. F. Sahlberg from Sitka (Alaska, USA) .

Type material examined. One probable syntype is housed in Harvard ( MCZ, type no. 1160). Photos of labels and habitus are available from the database of insect primary types in the collection of MCZ (https://mczbase.mcz. harvard.edu/guid/ MCZ:Ent:1160). A second syntype is deposited in Helsinki ( MZH) and it was examined by I.S. in 2019. The specimen in MCZ has no geographic label and bears only Loew’s hand-written label with specific name. Other labels were probably attached by museum staff. The specimen in MZH bears the following labels: small lilac label [this label shows the origin from the collection of H. Loew] // Sitcha [printed] // F. Sahlberg [printed] // Phoneutisca bimaculata [Loew’s hand-written] // old Museum label // modern Museum label. Since Loew indicates in the original description “Sitcha, Sahlberg”, the syntype in MZH should be selected as the lectotype.

Additional material examined. CANADA. Alberta: Lake Louise , 29.vii.1935, A.L. Melander (4 ♀, USNM) ; Eisenhower Jct. 4700’, Banff, Mal. Trap , 7.vii.1962, Mason (2 ♂, CNC) ; Temple Chalet , 7000’, Banff Nat. Pk., 26.vii.1962, E. Mason (1 ♀, CNC) ; 10 km NW Whitecourt, Hwy 32 at Sakwatamau River (54.10N 115.42W), sweep vegetation at river edge, 15.vii.1997, T. A. Wheeler (1 ♂, 1 ♀, LEM) . British Columbia: Oliver , 28.iv.1923, C.B. Garrett (1 ♀, CNC) ; Fairmont , 28.vii.1926, A.A. Dennys (1 ♀, CNC) ; Yoho Val. , 30.vii.1935, A.L. Melander (1 ♀, USNM) ; Robson , viii.1947, H. R. Foxlee (1 ♀, CNC) ; Chilkat Pass , alt. 3200’, mi 94 border, 17.vii.1948, Mason & Hughes (1 ♂, 1 ♀, CNC) ; MacGillivray Creek, Game Reserve, nr. Chilliwack , 15.vi.1953, G.J. Spencer (1 ♀, CNC) ; same locality, 14.vii.1953, G.J. Spencer (1 ♂, CNC) ; same locality, 23.vii.1953, G.J. Spencer (1 ♀, CNC) ; Hatzic Lake , 24–26.vii.1953, W. R. M. Mason (1 ♂, 2 ♀, CNC) ; Summit Lake, mi 392, Alaska Hwy , 4200’, 19–21.vii.1959, R. E. Leech (1 ♂, CNC) ; Gagnon Rd. , 6 mi. W of Terrace, 220’, scrub poplar and low vegetation, in dandelion meadow, 8.vi.1960, W.W. Moss (1 ♂, 2 ♀, CNC) ; same locality, in marshy clearing, 8.vi.1960, J.G. Chillcott (6 ♂, CNC) ; Terrace , along railroad, 8.vi.1960, J.G. Chillcott (2 ♀, CNC) ; same locality, 19.vii.1960, C.H. Mann (1 ♀, CNC) ; 32 mi. SW of Terrace , wet thick poplar cedar forest, 6.vi.1960, J.G. Chillcott (2 ♀, CNC) ; same locality, in cut over area low shrubs, 11.vi.1960, J.G. Chillcott (1 ♂, 3 ♀ CNC) ; same locality, 5.vii.1960, J.G. Chillcott (1 ♂, 1 ♀, CNC) ; same locality, cutover swampland, 9.vii.1960, J.G. Chillcott (1 ♀, CNC) ; same locality, 100’, 13.vii.1960, J.G. Chillcott (1 ♀, CNC) ; same locality, 6.vi.1960, C.H. Mann (1 ♀, CNC) ; same locality, 8.vi.1960, C.H. Mann (1 ♂, 2 ♀, CNC) ; same locality, 6.vii.1960, C.H. Mann (1 ♂, 6 ♀, CNC) ; same locality, 11.vii.1960, C.H. Mann (1 ♂, CNC) ; same locality, flowers of Heracleum , 6.vi.1960, R. Pilfrey (1 ♀, CNC) ; Lakelse L., bog nr. Terrace , 11.vii.1960, C.H. Mann (1 ♂, CNC) ; same locality, 14.vi.1960, C.H. Mann (1 ♂, 1 ♀, CNC) ; Kleanza Creek , 14 mi. E of Terrace, B.C., 13.vii.1960, W. R. Richards (1 ♀, CNC) ; Pr. Rupert , wet grassy marsh, 18.vii.1960, C.H. Mann (1 ♀, CNC) ; Jet. Pr. Rupert-Port Edward Hwy. , 18.vii.1960, C.H. Mann (1 ♂, 1 ♀, CNC) ; 10 mi. E, Pr. Rupert, Ledum-Kalmia bog, 4.vi.1960, C.H. Mann (1 ♂, CNC) ; Airport area, Terrace , 4.viii.1960, C.H. Mann (1 ♂, CNC) ; Shames , 18 mi. SW Terrace, 24.vii.1960, C.H. Mann (1 ♀, CNC) ; Port Edward , 18.vii.1960, C.H. Mann (1 ♂, CNC) ; same locality, 18.vii.1960, B. Heming (1 ♂, 3 ♀, CNC) ; Zymagotitz River , 6 mi. W Terrace, 190’, 20.vi.1960, R. Pilfrey (1 ♀, CNC) ; Ketchum L., 131°45′ 58°22′, 3600’, dry sedge grass and moss bogs, 26.viii.1960, R. Pilfrey (1 ♂, CNC) ; Pr. Rupert, Ledum-Kalmia bog, 4.vi.1960, R. Pilfrey (1 ♂, 1 ♀, CNC) ; Pr. Rupert, wet grassy marsh, 18.vii.1960, R. Pilfrey (1 ♀, CNC) ; 18 km N Revelstoke , 3.vii.1989, A. Borkent (CD1052) (1 ♂, CNC) ; 10 km SW Anahim Lake , 3–5.vii.1992, A. Borkent (CD1422) (1 ♂, 1 ♀, CNC) ; 40 km E Enderby , 10.vii.1992, A. Borkent (CD1432) (3 ♂, 3 ♀, CNC) ; 29 km SE Hope , 14.vii.1994, A. Borkent (CD1760) (2 ♂, CNC) ; Exchamsiks River , 58 km SW of Terrace, N54°20.00′ W129°17.81′, MT, 17–18.viii.2008, S.E. Brooks & J.M. Cumming (1 ♂, 6 ♀, CNC) ; same locality, YPT, 15–17.viii.2008, S.E. Brooks & J.M. Cumming (3 ♀, CNC) ; same data, MT, Cumming (5 ♀, CNC) ; same locality, MT, 15.viii.2008, Cumming (1 ♀, CNC) ; same locality, MT, 18.viii.2008, S.E. Brooks (8 ♂, 11 ♀, CNC) . Manitoba: Eastern Cr. nr. Churchill , 9.vii.1952, J.G. Chillcott (1 ♂, CNC) ; Fort Churchill , 10.vii.1952, J.G. Chillcott (1 ♀, CNC) ; Mile 505, Hudson Bay Ry., 22.vii.1952, J.G. Chillcott (1 ♀, CNC) . Northwest Territories: Reindeer Depot, Mackenzie Delta , 13.vii.1948, J. R. Vockeroth (1 ♀, CNC) ; Aklavik , 3.vii.1956, E.F. Cashman (1 ♀, CNC) ; Hodgeson Lk., Norman Wells , 4.vii.1969, G.E. Shewell (1 ♂, CNC) . Quebec: Ft. Chimo [= Kuujjuaq ], 5.vii.1958, W. R. M. Mason (1 ♂, CNC) ; Chimo , 17–18.viii.1959, W. R. M. Mason (1 ♀, CNC) . Yukon: Whitehorse , 5.viii.1948, Mason & Hughes (1 ♀, CNC) ; Marsh Lake , 9.viii.1948, Mason & Hughes (1 ♀, CNC) ; 14 mi. E Dawson , 1300’, 29.vii.1962, R.E. Leech (1 ♀, CNC) ; North Fork Crossing, mi. 43 Peel Plt. Rd. , 3500’, on Salix , 3.vii.1962, R. E. Leech (3 ♂, 3 ♀, CNC) ; same locality, 6.vii.1962, R.E. Leech (12 ♂, 10 ♀, CNC) ; same locality, on Salix , 25.vi.1962, R.E. Leech (1 ♀, CNC) ; Morley River , 25.vi.1989, P.H. Arnaud Jr. (1 ♂, USNM) ; Klondike Hwy, 15 km S Carmacks, Nordenskiold River , sweep along river edge, 29.vi.1997, T. A. Wheeler (1 ♀, LEM) ; Emerald Lake (60.15.8N 134.45.1W), sweep at lake margin, 20.vii.1998, T. A. Wheeler (1 ♀, LEM) . USA. Alaska: ex. Alder; Matanuska , 7.x.1944, J.C. Chamberlin (2 ♀, USNM) ; Umiat , 14.vii.1950, R. Madge (1 ♂, CNC) ; King Salmon, Naknek R., 1–3.viii.1951, W. R. Mason (1 ♂, 1 ♀, CNC) ; Big Delta , 24.vi.1951, W. R. M. Mason (2 ♀, CNC) ; same locality, 24.vi.1951, J. R. McGillis (1 ♀, CNC) ; same locality, 30.vi.1951, Mason (1 ♂, CNC) ; Mile 315, Edward Hwy. , 7.vi.1951, W. R. M. Mason (2 ♀, CNC) ; Mile 289, Edward Hwy. , 27.vi.1951, W. R. M. Mason (1 ♀, CNC) ; Summit L., mi. 199, Isabella Pass , 3.viii.1951, W. R. M. Mason (1 ♂, 6 ♀, CNC) ; Summit L., Isabella Pass , 9.vii.1951, W. R. M. Mason (1 ♂, CNC) ; Mile 315, Edward Hwy. , 8.vi.1951, W. R. M. Mason // Tachydromia bimaculata , det. B.E. Cooper (1 ♂, 1 ♀, CNC) ; Sebreo Is. , 22.vii.1965 // D.M. DeLong Coll. (1 ♀, USNM) ; Tangle Lakes , Malaise trap, 28.vi–8.vii.1969, J. Matthews (1 ♀, CNC) . Colorado: Corona Pass , Boulder Co., 10600’, 11.viii.1961, J.G. Chillcott (1 ♀, CNC) ; Echo L. 10600’, Mt. Evans , 24–25.vii.1961, C.H. Mann (2 ♀, CNC) ; Cottonwood Pass , Gunnison Co., 11000’, 29.vii.1961, J.G. Chillcott (1 ♀, CNC) ; Echo L., 9600’, Mt. Evans , 26.vii.1961, B.H. Poole (1 ♂, CNC) ; Echo L., 10600’, Mt. Evans , 24.viii.1961, C.H. Mann (1 ♀, CNC) . Nebraska: Santee , 11.vi.1963, F.C. Harmston (1 ♀, USNM) . Washington: Bald Knob Campground, Mt. Spokane SP, Spokane Co., 4800–5200 ft., 6.vii.1978, W.J. Turner sweeping // N.E. Woodley Collection Donated 2002 // Tachydromia bimaculata (Loew) ♂, det. Turner 1979 (1 ♂, USNM) . Wyoming: Yellowstone Nat. Park, Sylvan Pass , 22.vii.1934, A.L. Melander (1 ♀, USNM) ; Union Pass Road , Fremont Co., along rocky stream, 8300’, 17.vii.1961, J.G. Chillcott (3 ♀, CNC) .

Diagnosis. The species is distinguished by the following combination of characters: palpus lacking black subapical seta; thorax with pale setation. Male: palpus bicoloured, pale yellow basal portion nearly as long as black apical portion, with deep apical excision; fore and mid legs extensively yellow.

Redescription. Male ( Fig. 2A ). Length: body 1.8–2.0 mm, wing 1.6–1.9 mm. Head with occiput densely greyish pruinose on upper part (including vertex) and shiny on lower part (except very narrow postocular space); pale setose; 2 moderately long vertical setae, some short setae around neck, near mouth-opening and minute postoculars. Ocellar triangle shiny; ocellars moderately long (nearly as long as verticals), inclinate. Frons shiny, slightly broadened above. Face pruinose; clypeus shiny. Antenna with scape and pedicel yellow, postpedicel and stylus brown. Postpedicel egg-shaped; stylus subapical, nearly 2.0 times as long as pedicel and postpedicel combined. Proboscis blackish brown. Palpus ( Fig. 2B, C ) bicoloured, black and bilobate apically; somewhat longer than proboscis; pale yellow basal portion nearly as long as black apical portion; covered with scattered pale setulae.

Thorax entirely black, largely shiny, with pale setation; prothoracic sclerites (except postpronotal lobe) densely whitish grey tomentose, scutellum and postnotum greyish tomentose. Postpronotal lobe large, elongate oval, lacking conspicuous setae, with scattered minute setulae. Mesonotum with 1 long notopleural, 1 very short postalar and 4 scutellars (cruciate apicals nearly as long as notopleural seta, laterals somewhat shorter); some minute setulae present behind postpronotal lobe and on notopleural depression anteriorly; acrostichals absent; dorsocentrals uniserial, scattered, mostly minute, 1 prescutellar pair somewhat longer (nearly as long as postalar seta).

Leg colour (somewhat variable, especially in females): fore coxa and trochanter yellow, mid and hind coxae and trochanters brown (mid coxa and trochanter sometimes somewhat paler); fore and mid femora yellow to dusky yellow with distinct brownish dorsal stripe, hind femur entirely blackish brown; fore and mid tibiae yellow to dusky yellow, hind tibia brownish; tarsi brownish (tarsomeres 1–2 yellowish near base). Fore coxa clothed in numerous pale setae of different lengths; fore coxa whitish grey pruinose anteriorly, mid and hind coxae with patch of similar pruinosity laterally. Fore femur thickened; whitish pubescent ventrally, with short anteroventral and posteroventral pale setulae becoming longer basally. Fore tibia spindle-shaped, with unmodified setation. Mid femur slightly slenderer than fore femur, with row of 5–6 black, anteroventral spine-like setae on apical half and row of black posteroventrals including 5–6 spine-like setae on apical half and about 6 strong yellowish setae closer to base. Mid tibia lacking apical projection; bearing ventral, black spinule-like setulae (5–6 subapicals shifted on anteroventral face and erect) and 2 ventral, closely set, long, subapical strong black setae. Hind femur unmodified, lacking prominent setae. Hind tibia and tarsus unmodified.

Wing normally developed, rounded at apex, with unmodified venation; wing membrane largely faintly brownish infuscate, with indistinct larger brownish patch below meeting of vein R 1 with costa and distinct smaller patch near meeting of vein R 2+3 with costa. One very short basal costal seta present. Vein R 2+3 straight, thickened and strongly turned towards costa subapically (angle varying; in addition, rarely, short subapical appendix present). Veins R 4+5 and M 1 parallel, close to each other. Vein M 4 distinct throughout. Crossveins r-m and bm-m broadly separated. Cell r 1 slightly broader than cells r 2+3 and r 4+5. Calypter brownish, with scattered fringe. Halter with brownish yellow stem and pale knob.

Abdomen black, shiny; tergites narrowly faintly pruinose laterally, with scattered setulae, sternites with more numerous setulae, sternite 8 with longer posteromarginal setae; pregenital segments unmodified (except segment 8).

Hypopygium ( Fig. 3 ) black, small, elongate oval. Right epandrial lamella subtriangular (lateral view), with several unmodified moderately long setae apically, lacking additional lobes. Right surstylus ( Fig. 3B ) separated from epandrial lamella, small, subtriangular (lateral view), bent inwards, with several submarginal spinules ventrally. Left epandrial lamella small, lacking prominent setae. Left surstylus ( Fig. 3C ) barely separated from epandrial lamella, elongate, broadly ovate apically, with several unmodified, moderately long setae. Hypandrium with 4 short setae. Cerci ( Fig. 3A ) separated, elongate oval, of subequal lengths, with some unmodified moderately long setae. Hypoproct subtriangular (dorsal view), not produced beyond apices of cerci.

Female ( Fig. 2D ). Palpus ( Fig. 2E ) unicoloured, yellow, long (at least as long as proboscis), slender, pointed apically, covered with scattered pale setulae. Legs varying in colour but usually darker, with fore and mid femora largely brownish and fore and mid tarsi entirely brownish. Mid femur with thin setae of different lengths closer to base but bearing rows of black spinules apically as in male. Mid tibia lacking erect subapical spinules, with 2 very short, closely set subapical setae. Otherwise as in male. Cercus brownish, long, slender, with minute setulae.

Remarks. Tachydromia bimaculata belongs to the T. punctifera group of species sensu Chvála (1975). The species is common in boreal and arctic regions of North America. Tachydromia bimaculata was very recently recorded from Finnish Lapland ( Kanavalová et al. 2019).

Distribution. Holarctic. North America: Canada (Alberta, British Columbia, Manitoba, Northwest Territories, Quebec, Yukon), USA (Alaska, Colorado, Nebraska, Washington, Wyoming). Eurasia: Finland.

Figures

FIGURE 2. Tachydromia bimaculata (Loew) (Canada, British Columbia; CNC). A. Male habitus, lateral view. B. Male head, anterior view. C. Male palpus, dorsal view. D. Female habitus, lateral view. E. Female head, anterior view. Abbreviation: plp—palpus.

FIGURE 3. Tachydromia bimaculata (Loew), male terminalia (Canada, British Columbia; CNC). A. Hypopygium, dorsal view. B. Right surstylus, lateral view. C. Left epandrial lamella and left surstylus, lateral view. Abbreviations: cerc—cercus; lft sur—left surstylus; rt sur—right surstylus. Scale bar is 0.1 mm.