Tachyempis agens ( Melander, 1910 )

Shamshev, I. V. & Grootaert, P .., 2024, Revision of the Nearctic species of the genus Tachyempis Melander, 1928 (Diptera: Hybotidae), Russian Entomological Journal 33 (1), pp. 124-135 : 127-128

Tachyempis agens ( Melander, 1910)

Figs 1 , 4–6 .

Tachydromia agens Melander, 1910: 59 (♂ and ♀), figs 2 (head and thorax), 19 (wing). Type locality: USA, Washington, Pullman .

NOTES ON TYPE SERIES. Melander [1910] reported the following material: “ Type male collected on a windowpane July 3, 1906, in my house at Pullman, Washington. Type female taken in a wheat field nine miles west of Baird , Washington, June 23, 1908. I have also five mounted paratypes which I collected at Lynden , Baird , and Pullman , all in Washington State ” .

TYPE MATERIAL EXAMINED. Holotype, ♂, labelled: Pullman Wash. / 3 July 06 // TYPE / Tachydromia / agens ♂ / Mel. [red label, hand-written] // AL Melander / Collection / 1961 ( USNM). Paratypes. Baird, 6.23.08, Wash. // Type, Tachydromia agens ♀ Mel. [red label, hand-written] // AL Melander Collection 1961 (1 ♀, USNM); Pullman, Wash., 10July 1908 // Paratype Tachydromiaagens Mel.//ALMelander Collection 1961 (1 ♀, USNM); Linden, Wash., Jul. 29.08 // Paratype Tachydromia agens Mel. // AL Melander Collection 1961 (1 ♀, USNM); Pullman, Wash., 16 June 1912 // Paratype Tachydromia agens Mel. // AL Melander Collection 1961 (1 ♀, USNM); Linder, Wash., Jul. 22.08 // Paratype Tachydromia agens Mel. // AL Melander Collection 1961 (1 ♂, dissected, USNM).

ADDITIONAL MATERIAL EXAMINED. USA, Idaho: Lewiston, ID, 26.vi.1926, AL Melander / AL Melander Collection 1961 (1 ♀, USNM); Moscow Mt. , Idaho, 4.vii.1916 / AL Melander Collection 1961 (1 ♀, USNM) . Washington: Union Flat, Wash., 16.vi.16 / AL Melander Collection 1961 (1 ♂, USNM) .

DIAGNOSIS. Small species with entirely greyish pruinose occiput, vertex, frons and thorax; head and thorax with pale setae; palpus subrectangular, clothed in whitish pubescence giving to palpus silvery glisten in some view; pale yellow in male, dusky yellow in female; legs mostly tawny, fore coxa and fore femur paler ventrally.

REDESCRIPTION. Male. Length: body 1.3–1.5 mm, wing 1.4–1.5 mm. Head black, with pale setation. Occiput and vertex entirely greyish pruinose; 2 moderately long, wide apart, lateroclinate verticals; some scattered, short, fine setae on lower part of occiput, row of minute postoculars, some longer setae near mouth-opening. Ocellar triangle greyish pruinose; 2 moderately long lateroclinate ocellars. Frons entirely greyish pruinose; near anterior ocellus nearly 2 times broader than near antennae; margins slightly bowed outwardly opposite ocellar triangle and nearly parallel above antennae; above antennae 2.5–3.0 times as broad as anterior ocellus. Antenna with scape and pedicel reddish brown, postpedicel and stylus brown; postpedicel very small, slightly broader than high; stylus subapical, rather long, 4.0–5.0 times as long as pedicel and postpedicel combined, microscopically pubescent. Proboscis brown, short. Palpus unmodified, broad, subrectangular, pale yellow (usually slightly darkened apically), clothed in whitish pubescence giving to palpus silvery glisten in some view, with 3–4 yellow submarginal setae of different lengths.

Thorax entirely blackish brown, uniformly faintly greyish tomentose, with pale setation. Postpronotal lobe rather subglobular, with 1 moderately long inclinate seta and several minute setulae. Mesonotum usually with 1 long notopleural (sometimes 2, then anterior seta short), 2–3 minute setulae on postsutural supra-alar face, 1 short postalar and 4 scutellars (setae of apical pair long inclinate, lateral pair short); some minute setulae present behind postpronotal lobe and on notopleural depression anteriorly; acrostichals minute, arranged in 1–2 rows, lacking on prescutellar depression; dorsocentrals mostly uniserial and minute, 1–2 prescutellar pairs longer.

Legs colour: fore coxa yellow, mid and hind coxae brown; otherwise legs tawny, fore femur ventrally and knees of fore leg usually somewhat paler. Legs with pale setation. Fore coxa faintly whitish pruinose anteriorly. Trochanters with unmodified setation. Fore femur thickened; faintly whitish pubescent ventrally; bearing short anteroventral and posteroventral setae becoming longer closer to base. Fore tibia slightly thickened, with unmodified setation. Mid femur unmodified, slender; with anteroventral and longer posteroventral setae becoming longer closer to base, bearing several moderately long setae near base anteriorly. Mid tibia unmodified, with more or less distinct ventral spinule-like setulae, lacking apical projection. Hind femur and tibia unmodified, lacking prominent setae. Tarsomeres of all legs unmodified, lacking prominent setae.

Wing normally developed, rounded at apex, with unmodified venation; membrane lacking prominent pattern, uniformly faintly infuscate. One short basal costal seta present. Second section of costa nearly 1.5 times longer than third section. Rs about 2 times longer than basal portion of R 4+5. Vein R 2+3 evenly arched towards costa. Veins R 4+5 and M

1+2

parallel near wing-apex. Apical portion of vein M

4

(= Cu 1 by authors) slightly longer than its basal portion. Crossveins r-m and bm-m broadly separated; r-m closer to apex of cell bm than to its middle; bm-m slightly oblique (sometimes nearly transverse). Cell bm broad, nearly 1.5 times broader than cell br. Cell r 1 nearly 2.5 times narrower than cell r 2+3. Calypter brownish, with pale cilia. Halter with pale knob and brownish stem.

Abdomen black brown, subshiny, faintly greyish pruinose; covered with scattered minute pale setulae; pregenital segments with rather short posteromarginal setae.

Hypopygium ( Figs 4–6 ) moderately large, brown, elongate oval. Right epandrial lamella elongate oval, somewhat produced mid-ventrally, bearing scattered, simple setae. Right surstylus ( Figs 4, 5 ) differentiated, digitiform, mostly narrow, broad near base, very long, overlapping hypopygium posteriorly; bearing 3 blunt-tipped spines on upper margin near base, 1 spine-like seta near base on internal face, 4 moderately long strong setae dorsally, scattered marginal setulae. Left epandrial lamella ( Figs 4, 6 ) slightly shifted anteriad relative to right epandrial lamella (dorsal view); basal apodeme inconspicuous; with short, digitiform apical projection bearing scattered setulae apically; 3 moderately long marginal setae closer to base of left cercus. Left surstylus ( Fig. 6 ) barely differentiated from epandrial lamella, elongate oval, moderately large, with moderately long setae along dorsal margin and at apex; without internal projection. Cerci ( Fig. 4 ) broadly separated; right cercus moderately large, digitiform (dorsal view), bearing moderately long simple setae somewhat stronger apically; left cercus shifted anteriad relative to right cercus, elongate oval, broad, bearing short to moderately long simple setae. Subepandrial sclerite semicircular, with 2 spine-like setae.

Female ( Fig. 1 ). Palpus dusky yellow, darker anteriorly. Antenna often entirely brown. Otherwise as in male. Abdominal segments 7–8 densely pruinose. Cercus moderately long, slender, with scattered setulae.

REMARKS. The holotype is in good condition but left antenna missing. Melander [1910] noted this species actively running about the ground and stalks in wheat fields.

An undescribed species mentioned above (collected from Arizona ( USA)) resembles T. agens sharing pale setose thorax and a postpronotal seta. However, it can be readily distinguished from T. agens primarily by narrow, elongate oval palpus, narrower frons and clearly yellow scape and pedicel of the antenna.

DISTRIBUTION. USA (Idaho, Washington) .

Figures

Figs 1–3. Tachyempis Melander, habitus: 1 — T. agens (Melander), ♀, paratype, antero-lateral view; 2 — T. calva (Melander), ♂, lateral view; 3 — T. universalis (Melander), ♂, lateral view. Рис. 1–3. Tachyempis Melander, габитус: 1 — T. agens (Melander), ♀, паратип, вид спереди и сбоку; 2 — T. calva (Melander), ♂, вид сбоку; 3 — T. universalis (Melander), ♂, вид сбоку.

Fig. 4–6. Tachyempis agens (Melander), ♂: 4 — hypopygium, dorsal view; 5 — right surstylus, lateral view; 6 — left epandrial lamella, lateral view.Abbreviations: epand — epandrium; epand apod — epandrial apodeme; goncx apod — gonocoxal apodeme; hypd — hypandrium; hyprct — hypoproct; lft cerc — left cercus; lft sur — left surstylus; rt cerc — right cercus; rt sur — right surstylus; sbepand scl — subepandrial sclerite. Scale bar is 0.1 mm. Рис. 4–6. Tachyempis agens (Melander), ♂: 4 — гипопигий, вид сверху; 5 — правый сурстиль, вид сбоку; 6 — леваЯ лопасть ЭпандриЯ, вид сбоку. СокращениЯ: epand — Эпандрий; epand apod — ЭпандриальнаЯ аподема; goncx apod — гонококсальнаЯ аподема; hypd — гипандрий; hyprct — гипопрокт; lft cerc — левый церк; lft sur — левый сурстиль; rt cerc — правый церк; rt sur — правый сурстиль; sbepand scl — субЭпандриальный склерит. Масштаб: 0,1 мм.