Tachyempis calva ( 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 : 128-130

Tachyempis calva ( Melander, 1910)

Figs 2 , 7–10 .

Tachydromia calva Melander, 1910: 58 (♀), fig. 18 (wing). Type locality: USA, Georgia, Tifton .

NOTES ON TYPE SERIES. Melander [1910] provided the following data: “Described from a single female, presumably collected by Mr. G. R. Pilate as it bears the label, Tifton, Georgia, Sept. 25, 1896 ” .

TYPE MATERIAL EXAMINED. Holotype, ♀, labelled: Tifton, Ga. / Sept. 25 '96 // TYPE / T. calva / Mel. [red label, hand-written] // AL Melander / Collection / 1961 ( USNM).

ADDITIONAL MATERIAL EXAMINED. USA, North Caroline : Southport NC, 10.x.1948, SW Sabrosky / ♂; Tachyempis ( ? calva Mel. ), det. Sabrosky (2 ♂♂, USNM) .

DIAGNOSIS. Small species with shiny frons and vertex (including ocellar triangle); head and thorax with black setae; palpus elongate oval, pale, silvery white pubescent, with 1 short, dark, subapical seta; postpronotal lobe and mesoscutum subshiny; legs extensively yellow, hind femur mostly brownish (except base).

REDESCRIPTION. Male ( Fig. 2 , described for the first time). Length: body 1.5–1.6 mm, wing 1.6 mm. Head black. Occiput (except narrow postocular space) greyish pruinose; 2 rather moderately long, black, wide apart, lateroclinate verticals; some scattered, short, fine brownish to brownish yellow setae on lower part, row of minute postoculars, some longer pale setae near mouth-opening. Vertex shiny, including ocellar tubercle; 2 moderately long, black, lateroclinate ocellars. Frons shiny, broadly V-shaped, near anterior ocellus about 2 times broader than near antennae, with straight margins, above antennae about 2.5–3.0 times as broad as anterior ocellus. Antenna brown; postpedicel small, rather drop-like, nearly as long as wide; stylus arising somewhat dorsoapically, long, about 4.0 times as long as pedicel and postpedicel combined; short pubescent. Proboscis brown, short. Palpus unmodified, elongate ovate, short, pale, clothed in numerous minute silvery white setulae giving to palpus silvery glisten in some view; with some scattered, short, pale setae, bearing 1 dark, slightly stronger subapical seta.

Thorax entirely brown to black; with postpronotal lobe and mesoscutum almost shiny, scarcely pale grey tomentose (more distinct in anterior view); prosternum, proepisternum, scutellum and entire mesopleuron somewhat denser tomentose. Postpronotal lobe elongate oval, lacking prominent setae, with scattered minute setulae. Mesonotum with 1 black, long, strong notopleural, 3 minute setulae on postsutural supra-alar face, 1 minute postalar and 4 scutellars (apical pair long, strong, inclinate, lateral pair minute); some minute setulae present behind postpronotal lobe and on notopleural depression anteriorly; acrostichals minute, arranged in 1–2 rows, lacking on prescutellar depression; dorsocentrals arranged in 1–2 rows, minute throughout.

Legs colour: largely yellow; fore and mid femora somewhat brownish yellow on subapical part dorsally (mid femur darker), hind femur brownish on about apical 2/3–3/4 [in holotype 2/3 but not 1/2 as Melander indicates]; fore and mid tibiae brownish yellow near base; tarsomere 5 of all legs brown. Coxae clothed in pale setae of different lengths, fore coxa faintly whitish pruinose anteriorly. Trochanters with unmodified setation. Fore femur thickened, faintly whitish pubescent ventrally, bearing short anteroventral and posteroventral pale setae becoming longer near base. Fore tibia spindle-shaped, with row of stronger ventral setulae. Mid femur unmodified, slender, with anteroventral and longer posteroventral pale setulae becoming longer near base. Mid tibia unmodified, with quite prominent ventral spinule-like setulae, lacking prominent 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; lacking prominent pattern, uniformly faintly infuscate. One very short costal seta present. Second section of costa slightly longer than third section (nearly 1.4 times). Vein R 2+3 arched towards costa on basal portion. Rs nearly as long as basal portion of R 4+5. Veins R 4+5 and M 1+2 parallel near wing-apex. Apical portion of M 4 slightly longer than its basal portion. Crossveins r-m and bm-m broadly separated; bm-m transverse. Cells br and bm of subequal width. 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 setulae; pregenital segments with long posteromarginal setae.

Hypopygium ( Figs 7–10 ) moderately large, brown, elongate oval. Right epandrial lamella elongate oval, somewhat produced mid-ventrally ( Fig. 8 ), bearing scattered, simple setae. Right surstylus ( Figs 7–9 ) differentiated, nearly digitiform, rather broad, long, overlapping terminalia posteriorly; bearing 2 long closely set setae near base dorsally, with some scattered marginal setulae. Left epandrial lamella ( Fig. 10 ) strongly shifted anteriad relative to right epandrial lamella (dorsal view); rounded apically, with large basal apodeme; 2 long setae on subapical part. Left surstylus ( Fig. 10 ) barely differentiated from epandrial lamella, nearly elongate oval, rather small, with moderately long setae along dorsal margin and at apex; with slender internal projection bearing scattered setulae at apex. Cerci ( Fig. 7 ) separated; left cercus shifted anteriad relative to right cercus, basal portion slightly produced inside epandrium; right cercus small, rather subtriangular (dorsal view), bearing moderately long simple setae; left cercus digitiform, broadened at base and very slender apically, gently arched (left lateral view), in left lateral view longer than left surstylus, bearing cluster of several moderately long setae on broadened basal portion. Subepandrial sclerite semicircular, bare.

FEMALE. Abdomen paler, rather yellowish brown (it is difficult to conclude weather this condition refers to sexual dimorphic characters but most probably that the holotype was described after paler specimen). Otherwise as in male. Apical abdominal segments missing.

REMARKS. The holotype is in poor condition: head, left fore leg and tarsomere 5 of right fore leg, tarsomeres 2–5 of right mid leg, right hind leg and apical part of abdomen (from segment 5) are lost.

DISTRIBUTION. USA ( Georgia, North Caroline).

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. 7–10. Tachyempis calva (Melander), ♂: 7 — hypopygium, dorsal view; 8 — right epandrial lamella and hypandrium, ventral view; 9 — right surstylus, lateral view; 10 — left epandrial lamella, lateral view. Abbreviations: epand — epandrium; epand apod — epandrial apodeme; goncx apod — gonocoxal apodeme; hypd — hypandrium; lft cerc — left cercus; lft sur — left surstylus; rt epand lam — right epandrial lamella; rt sur — right surstylus. Scale bar is 0.1 mm. Рис. 7–10. Tachyempis calva (Melander), ♂: 7 — гипопигий, вид сверху; 8 — праваЯ лопасть ЭпандриЯ и гипандрий, вид сниЗу; 9 — правый сурстиль, вид сбоку; 10 — леваЯ лопасть ЭпандриЯ, вид сбоку. СокращениЯ: epand — Эпандрий; epand apod — ЭпандриальнаЯ аподема; goncx apod — гонококсальнаЯ аподема; hypd — гипандрий; lft cerc — левый церк; lft sur — левый сурстиль; rt epand lam — праваЯ лопасть ЭпандриЯ; rt sur — правый сурстиль. Масштаб: 0,1 мм.