Tachydromia diversipes Melander, 1910

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 : 162-163

Tachydromia diversipes Melander

( Fig. 5 )

Tachydromia diversipes Melander, 1910: 55 (as T. schwarzii var.). Type locality: USA, Texas, Austin .

Tachydromia schwarzii : Melander, 1902: 225 (part).

Notes on type series. Melander (1910) described this species based on the male sex only. He noted the following material: “ two males which I captured at Dry Creek, near Austin, Texas, April 20, 1901”.

Type material examined. SYNTYPE ♂, labelled: Austin, Tex [ Texas] 4.20.1 [20.iv.1901] // Dry Creek // Paratype [label attached later], Tachydromia diversipes Mel. [species name hand-written] // A.L. Melander Collection 1961 // Tachydromia diversipes Mel. [hand-written] ( USNM).

Additional material examined. USA. Texas: Kerrville , on seepage under overhanging rock, 30.iii.1959, J.F. McAlpine (2 ♀, CNC) .

Diagnosis. The species is distinguished by the following combination of characters: palpus yellowish brown; proepisternum tomentose on about lower half only; legs extensively yellow, male fore tibia black on apical 1/3 anteriorly; wings normally developed, with entirely separated bands.

Redescription. Male. Length: body 1.9 mm, wing 1.7 mm. Head with occiput (including vertex) extensively shiny, only with patch of pruinosity above neck; 2 long, black vertical setae, some pale setae around neck and near mouth-opening and row of short postoculars. Ocellar triangle shiny, ocellars short. Frons shiny, slightly broadened towards ocellar triangle, narrow, above antennae 1.5–2.0 times as broad as anterior ocellus. Antenna brownish yellow, stylus brownish. Postpedicel subglobular, small; stylus subapical, very long. Proboscis brownish. Palpus unmodified, elongate oval, somewhat shorter than proboscis, yellowish brown; clothed in scattered black setulae, with 2 short, black subapical setae.

Thorax entirely black, largely shiny; prosternum entirely and proepisternum on lower part densely whitish grey tomentose, proepisternum on upper part and meron posteriorly subshiny, faintly tomentose; scutellum and postnotum tomentose. Postpronotal lobe large, elongate oval, lacking conspicuous setae, with scattered minute setulae. Mesonotum with 1 black, moderately long notopleural, 1 very short postalar and 4 scutellars; some minute setulae present behind postpronotal lobe and on notopleural depression anteriorly; acrostichals lacking; dorsocentrals uniserial, numerous, mostly minute, 1 prescutellar pair nearly as long as scutellar lateral setae.

Leg colour: coxae and trochanters yellow; fore and mid femora almost entirely yellow, somewhat brownish on apical half dorsally, hind femur largely brown, yellow on about basal 1/5; fore tibia yellow on basal 2/3, with black stripe abruptly filling apical 1/3 anteriorly, mid and hind tibiae almost entirely brown (except extreme base); fore and mid tarsi only with tarsomere 5 brownish, hind tarsi with tarsomeres 4–5 brownish. Fore coxa clothed in numerous short, hair-like setae, whitish pruinose anteriorly. Fore femur thickened, whitish pubescent ventrally, with minute anteroventral and posteroventral yellowish setulae becoming longer closer to base. Fore tibia spindle-shaped, with unmodified setation. Mid femur slender, with minute anteroventral and longer posteroventral, dark, spinule-like setae; bearing 2 long yellowish setae near base. Mid tibia lacking apical projection, with hardly prominent, ventral spinule-like setulae. Hind leg unmodified, lacking prominent setae.

Wing normally developed, rounded at apex, with unmodified venation; two broad, brownish, entirely separated bands. One short basal costal seta present. Vein R 2+3 slightly arched towards costa. Veins R 4+5 and M 1 slightly convergent towards wing apex. Crossveins r-m and bm-m broadly separated. Cell r 1 2.5–3.0 times narrower than cell r 2+3. Calypter brownish, with scattered fringe. Halter with pale knob and brownish yellow stem.

Abdomen brownish, shiny, covered with scattered setulae longer on pregenital segment. Abdominal segments 1–7 unmodified.

Hypopygium ( Fig. 5A–C ) large, elongate oval, blackish brown. Right epandrial lamella ( Fig. 5B ) rather subrectangular viewed laterally, bearing 5 unmodified long setae apically; ventral projection bearing 4 long, flattened setae. Right surstylus separated from epandrial lamella, as in Fig. 5B ; with simple, short setae. Left epandrial lamella ( Fig. 5C ) small, lacking prominent setae. Left surstylus not separated from epandrial lobe, elongate, excised apically, with several unmodified, short setae. Cerci ( Fig. 5A ) separated, with some unmodified moderately long setae; right cercus digitiform, narrow; left cercus somewhat shorter and broader than right cercus, with excision on right margin. Hypoproct slightly produced beyond apices of cerci.

Female (described for first time, Fig. 5D ). Fore tibia uniformly yellow. Otherwise as in male. Abdominal segments 6–8 greyish pollinose. Cercus long, slender, with minute setulae.

Remarks. Tachydromia diversipes belongs to the T. fuscinervis group ( Shamshev & Grootaert 2018). Melander (1910) noted that the syntypes were running over rather large stones in moist ravine at the base of Mount Barker.

Distribution. USA (Texas).

Figures

FIGURE 5. Tachydromia diversipes Melander (male: syntype, USA, Texas (USNM); female: Texas (CNC)). A–C. Male terminalia. A. Hypopygium, dorsal view. B. Right epandrial lamella and right surstylus, lateral view. C. Left epandrial lamella and left surstylus, lateral view. D. Female habitus, lateral view.Abbreviations: cerc—cercus; lft sur—left surstylus; rt sur—right surstylus. A–C: scale bar is 0.1 mm.