Thrypticus mediofuscus, Runyon, 2020

Runyon, Justin B., 2020, The Dolichopodidae (Diptera) of Montserrat, West Indies, ZooKeys 966, pp. 57-151 : 57

Thrypticus mediofuscus sp. nov. Figs 16 , 17

Type material.

Holotype, ♂ labelled: "MONTSERRAT:/ Sweetwater Ghaut/ 01 Aug 2005/ Yellow Pan Trap/ V.G. Martinson"; "HOLOTYPE/ ♂ Thrypticus / mediofuscus / Runyon [red label]" (USNM, type number USNMENT01350611). Paratypes: Dominica: 3 ♂, Springfield Estate, 1-3 June 2011, yellow pan trap, M.A. & L.L. Ivie; 1 ♂, St. Paul Parish, Springfield Estate, 29 May 2011, FIT with yellow pan, M.A. & L.L. Ivie. Montserrat: 1 ♂, rental house in Old Town, 16°44.79'N, 62°13.711'W, 80 m, yellow pan traps, 19 June 2017, J.B. Runyon (MTEC, USNM).

Description. Male (Fig. 16 ). Body length 1.7 mm, wing length 1.4 × width 0.5 mm. Head: Face wider than first flagellomere, dark brown with little to no violet reflections and very sparse light brown pruinosity, lower face with denser light brown pruinosity. Frons dark brown with strong violet reflections. Palpus yellow, slender, ovate with larger subapical yellow seta. Proboscis yellow with yellow marginal hairs. Antenna brown, often slightly dark reddish; first flagellomere rounded, very short, only slightly larger than scape; arista-like stylus apical. Lower postocular setae pale yellow to white, ventral-most seta distinctly larger. Thorax: Scutum dark metallic green with slight grayish pruinosity and strong violet reflections on anterior half; setae yellow to yellow-brown; ca. six pairs of small biseriate acrostichal setae, posterior-most acrostichal setae not distinctly diverging; five or six pairs of dorsocentral setae, posterior four pairs large, increasing in size posteriorly; scutellum with a pair of large marginal setae and minute seta on outer margin. Pleuron concolorous with scutum but more brownish above coxae II and III, without violet reflections; with a yellow seta on lower proepisternum. Legs: Wholly yellow with yellow to yellow-brown setae. Femur and tibia I without distinctive setae. Tibia II with large distally directed ad seta at 1/3 and ventral seta at apex; tibia III with row of very short erect comb-like setae (length ca. half width of tibia) on apical half dorsally and similar smaller row of such setae ventrally. Tarsomere I(1) with ventral row of very short erect comb-like setae (length <width of tarsomere). Ratios of tibia:tarsomeres: leg I: 18-8-4-3-2-3; leg II: 24-10-6-4-3-2; leg III: 28-6-8-5-3-3. Wing: Hyaline, oval, with light brown veins. Vein R2+3 essentially straight and diverging from R4+5 throughout, ending in costa near 4/5 of wing length; R4+5 curving slightly backwards on apical half of wing, approaching and subparallel to M1 near apex, half as far from M1 at apex than opposite crossvein dm-cu; M1 essentially straight beyond crossvein dm-cu, ending in wing apex; last part of CuA1 ca. 3.5 × longer than crossvein dm-cu. Calypter white with yellow-white setae. Halter knob and stem white. Abdomen: Tergites metallic dark green with slight bluish reflections, obscured by little or no pruinosity, setae yellow. Sternites brown with short pale brown setae. Hypopygium (Figs 16B , 17 ) on a short peduncle created by segments VI and VII. Epandrium dark brown with some metallic green reflections and sparse grayish pruinosity and two very small ventral lobes near apex each bearing a seta; hypopygial foramen left basolateral. Surstylus and cercus not spreading, forming a compact structure that in ventral view is oval with pointed apex; ventral lobe of surstylus pale yellow, shining, with four rather erect yellow ventral setae spaced along length; dorsal lobe of surstylus shining brown, with small hairs at apex. Cercus pale yellow, evenly rounded dorsally and covered with yellow hairs and two rows of slightly larger yellow setae. Phallus bifurcate at apex, with subquadrate membranous ventral lobe near base. Hypandrium with flexion and indentation near 2/3, caudate and membranous apically.

Female. Unknown.

Etymology.

This species is named for the dark middle appendage of the hypopygium (dorsal lobe of surstylus) of the male in lateral view (Fig. 16B ).

Distribution.

Dominica, Montserrat.

Remarks.

In Robinson (1975), Thrypticus mediofuscus keys to T. delicatus Robinson (holotype examined), but is distinguished by larger body size (1.2 mm in T. delicatus ), having coxa II wholly yellow (brownish in T. delicatus ), relative length of tarsomeres I(1, 2) as 2:1 (5:4 in T. delicatus ) and having dorsal lobe of surstylus dark brown (Figs 16B , 17 ; hypopygial appendages wholly yellow in T. delicatus ). Thrypticus mediofuscus is the only Thrypticus species in the Lesser Antilles with a bicolored surstylus, however, I have seen a related undescribed species from St. Lucia.

All specimens from both Montserrat and Dominica were collected in yellow pan traps.

Figures

Figure 16. Thrypticus mediofuscus sp. nov. A habitus of holotype male, left lateral B male terminalia, right lateral, arrow indicates darker middle hypopygial appendage (dorsal lobe of surstylus). Scale bars: 1.0 mm (A), 0.5 mm (B).

Figure 17. Thrypticus mediofuscus sp. nov. male terminalia, left lateral. Abbreviations: epand-epandrium; d sur-dorsal lobe of surstylus; hypand-hypandrium; T-tergite; v sur-ventral lobe of surstylus. Scale bar: 0.25 mm.