Tachydromia schwarzii Coquillett, 1895

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 : 185-187

Tachydromia schwarzii Coquillett

( Fig. 16 )

Tachydromia schwarzii Coquillett, 1895: 440 . Type localities: USA, “ Northern California and Utah ”.

Tachydromia hirtipes Melander, 1928: 282 . Type locality: USA, “near Viento , Oregon ”; syn. nov.

Notes on type series. Tachydromia schwarzii : Coquillett (1895) noted the following material: “ Types.—Nos. 3246 and 3247, U.S. N.M.; male and female. The Utah specimen was collected June 20, by Mr. E. A. Schwarz, after whom I take pleasure in naming this handsome species” .

Tachydromia hirtipes : Melander (1928) noted the following material: “ Eight males and five females, all collected on rocks in the mountain stream near Viento, Oregon, July 1, 1917, and Aug. 1, 1921 ”. Most syntypes are deposited in USNM, but one male and one female are in OUMNH (they were donated (or exchanged) by A.L. Melander to J.E. Collin) .

Type material examined. Tachydromia schwarzii : SYNTYPE ♂, labelled: StaCruz Mts. Cal. [= Santa Cruz Mts. California] // Type No 3246 U.S. N.M. [red label] // Tachydromia schwarzi Coq. [hand-written] ( USNM) .

Tachydromia hirtipes : SYNTYPES: ♂, Viento Oreg July 1, 1917 A.L. Melander // Paratype, Tachydromia hirtipes Mel. [red label, hand-written] // A.L. Melander Collection 1961 ( USNM) ; ♀, Viento Or 1 August ‘21 A.L. Melander // Allotype, Tachydromia hirtipes Mel. [red label, hand-written] ( USNM) .

Diagnosis. This species is distinguished in the male by long, hair-like setae on the fore femur, tibia and basitarsus; proepisternum shiny; wings with two broad brownish bands connected in cell r 1.

Redescription. Male. Length: body 2.3–2.5 mm, wing 2–2.2 mm. Head black. Occiput (including vertex) largely densely greyish pruinose, broadly shiny behind mouth-opening; 2 inclinate, moderately long, black vertical setae; some pale setae around neck and near mouth-opening; row of pale minute postoculars. Ocellar triangle pruinose, ocellars minute. Frons faintly greyish pruinose, nearly parallel-sided; above antennae nearly 3.0 times as broad as anterior ocellus. Antenna with brownish postpedicel and stylus, scape and pedicel somewhat paler. Postpedicel drop-like, short, nearly 1.5 times as long as wide; stylus nearly apical, very long, nearly 5.0 times as long as pedicel and postpedicel combined. Proboscis brown. Palpus unmodified, slender, long, somewhat shorter than proboscis, brownish; clothed in numerous long silvery setae, with 1 short (nearly half as long as palpus), black subapical seta.

Thorax black, mostly shiny; prosternum, scutellum and postnotum faintly greyish tomentose. Postpronotal lobe large, elongate oval, with numerous minute setulae; lacking conspicuous setae. Mesonotum with 1 black, moderately long notopleural, 1 short postalar and 4 scutellars (apical setae nearly as long as notopleural seta, lateral setae shorter); some minute setulae present behind postpronotal lobe and on notopleural depression anteriorly; acrostichals lacking; dorsocentrals uniserial, numerous, uniformly minute including prescutellar pair.

Leg colour: largely brownish (fore and mid legs generally slightly paler), coxae rather yellowish brown; knees, tibiae on extreme base, mid and hind tarsomeres 1–2 (except apex) yellowish [colour of legs variable; Melander’s specimens generally somewhat paler]. Fore coxa clothed in numerous pale hair-like setae. Fore femur strongly thickened, clothed in numerous, long, pale hair-like setae; whitish pubescence ventrally. Fore tibiae spindle-shaped, clothed in similar hair-like setae, longer ventrally and continuing on fore basitarsus. Mid and hind femora with rather long, dorsal hair-like setae on basal part. Mid femur slender, with shallow excavation near base; bearing 3 longer anteroventral yellowish setae before excavation and some blackish posteroventral spinule-like setae disappearing on apical half of femur. Mid tibia with short apical projection and shallow subapical excavation; bearing ventral spinule-like setulae. Hind leg with trochanter bearing 1–2 spinules dorsally.

Wing normally developed, rounded at apex, with unmodified venation; two broad brownish bands connected on cell r 1. One short costal seta present. Vein R 2+3 arched towards costa. Veins R 4+5 and M 1 convergent towards wing apex. Vein M 4 distinct throughout. Crossveins r-m and bm-m broadly separated. Cell r 1 very narrow. Calypter brownish, with scattered fringe. Halter with pale knob and brownish yellow stem.

Abdomen brownish, tergites pollinose, sternites shiny, covered with scattered dark setae somewhat longer on pregenital segments.

Hypopygium ( Fig. 16A–C ) rather small, elongate oval, blackish brown. Right epandrial lamella without ventral lobe, as in Fig. 16B . Right surstylus ( Fig. 16B ) separated from epandrial lamella, rather digitiform, somewhat elongate, with spinule-like, subapical marginal setae on inner side. Left epandrial lamella as in Fig. 16C . Left surstylus barely distinguishable from apex of epandrial lamella, short, with moderately long, simple setae apically. Right cercus ( Fig. 16A ) digitiform, rather long, rounded apically, covered with short setae; left cercus slightly shorter than right cercus, digitiform, covered with short setae.

Female. Fore leg with short setulae. Mid femur unmodified, with numerous minute setulae ventrally. Mid tibia unmodified. Hind trochanter lacking spinules. Otherwise as in male. Cercus long, slender, brownish, clothed in minute setulae.

Remarks. The records of this species from Texas and Washington ( USA) as well as from Mexico (Guerrero) ( Wheeler & Melander 1901; Melander 1902) need confirmation. In the female syntype of T. hirtipes , that we have examined, the frons and ocellar triangle are shiny.

Distribution. USA (California, Oregon,? Texas, Utah,? Washington),? Mexico.

Figures

FIGURE 16. Tachydromia schwarzii Coquillett, male terminalia (USA, California; syntype, USNM). A. Hypopygium, dorsal view. B. Right epandrial lamella and right surstylus, lateral view. C. Left epandrial lamella and left surstylus, lateral view. Abbreviations: cerc—cercus; epand—epandrium; hypd—hypandrium; lft sur—left surstylus; rt sur—right surstylus.A–C: scale bar is 0.1 mm.