Systenus ladonnae sp. nov.

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

Systenus ladonnae sp. nov. Figs 14 , 15

Type material.

Holotype, ♂ labelled: "MONTSERRAT: Cassava/ Ghaut, Beattie House/ 16°45.91'N, 62°12.95W / 04-23MAR2002, 632 ft./ A. Krakower, Malaise" "HOLOTYPE/ ♂ Systenus / ladonnae / Runyon [red label]" (USNM, type number USNMENT01350610). Paratypes: Dominica: 1 ♀, Cabrits National Park, East Cabrits Trail, 15.58564N, 61.47210W, Malaise, 30 May-7 June 2011, M.A. & L.L. Ivie. Montserrat: 1 ♂, same data as holotype, 23 March-3 April 2002, uv light, K.A. Marske; 1 ♂, Hill above Hope Ghaut, 16°45.17'N, 62°12.74'W, canopy fogging at dawn, 4 December 2002, 1,051 ft, J. Boatswain & J. Martin. Nevis: 1 ♂, Lover’s Beach, 17.20451N, 62.60577W, 21 March 2017, Malaise, W. Smithen; 1 ♀, same as previous, 26 April 2017. St. Kitts: 1 ♀, Dos d’Ane Pond Trail, 17°20.049'N, 62°48.012'W, Malaise, 31 July-12 August 2017 (MTEC, USNM).

Description. Male (Fig. 14A-C ). Body length 2.9 mm, wing length 2.6 × width 0.9 mm. Head: Face narrowed below but eyes distinctly separated (ca. five ommatidia wide at narrowest point); face and frons dark metallic green with some violet reflections, covered with thick grayish pruinosity. Palpus yellow with short black setae and one larger seta near apex. Proboscis yellow, keel-like, projecting anteriorly. Antenna (Fig. 14C ) with scape and pedicel yellowish, scape without dorsal setae; first flagellomere yellow on approximately basal third below, otherwise brown, subrectangular basally and abruptly narrowed to elongate tapering point in distal half, covered with short thick pubescence; arista-like stylus apical, short, length subequal to basal width of first flagellomere. Postcranium dorsally concave. Postocular setae in a single row, wholly white. Thorax: Scutum dark metallic green with a bronze stripe between acrostichal setae, covered with rather dense light gray pruinosity; posterior mesonotum distinctly flattened; ca. 12 pairs of biseriate acrostichal setae; six strong dorsocentral setae; scutellum with two pairs of large marginal setae, lateral pair smaller. Pleuron wholly green with dense light grey pruinosity; proepisternum with one strong ventrally projecting white seta above base of coxa I. Legs: Coxa I yellow with approximately basal half brown, with yellow setae on anterior surface, those near apex large; coxa II dark brown with yellow anterior setae, without lateral seta; coxa III dark brown with apex becoming yellow, with large yellow ad seta near 1/2. Remainder of legs yellow, except distal tarsomeres brownish. Femora lacking anterior preapical setae; femora II and III with ventral surface appearing fuzzy due to very short yellow microsetulae. Tibiae I and II covered with short ivory-colored vestiture; tibia I bare of major setae; tibia II with black dorsal and ad seta near 1/5, with two black apical setae anteriorly, remainder of apical setae very short; tibia III with 4-5 pd setae scattered along length. Tarsus III covered in short, stiff setulae which are longest ventrally (length subequal to width of tarsomeres). Ratios of tibia:tarsomeres: leg I: 18-8-5-3-2-2; leg II: 22-12-8-5-3-2; leg III: 26-5-12-6-4-3. Wing (Fig. 14B ): Hyaline, but with apical brown maculation between R4+5 and M1 that is immediately preceded by a similar-sized white spot with white microtrichia; vein R4+5 nearly straight then bent posteriorly near apex; vein M1 bowed beyond crossvein dm-cu so that veins R4+5 and M1 diverge and then converge near apex. Calypter yellow with fan of yellow-brown setae. Halter pale yellow. Abdomen: Metallic green with bronze reflections and dusting of gray pruinosity; posterior margin of tergite I with row of long brown to black setae, tergites otherwise covered with short brown to black setae. Sternites II-VI membranous or only weakly sclerotized, somewhat recessed; sternite VIII forming a setose cap-like cover over hypopygial foramen. Hypopygium (Fig. 15 ) on an elongate narrow peduncle formed by tergite and sternite VII that are separated by partially sclerotized pleural membrane, sternite VII glabrous, tergite VII setose. Hypopygial foramen left lateral near base. Epandrium dark brown, a little longer than wide. Surstylus yellow, antler-shaped, with rather large dorsal lobe before 1/2, small setae-bearing ventral lobe near 1/2, and long, slender finger-like apical lobe. Cercus yellow, with rounded swollen base, elongate and digitiform distally with many yellow setae. Phallus simple, rather broad throughout and narrowed near apex, arching dorsally on apical half. Hypandrium somewhat wishbone-shaped in ventral view, up curved distally in lateral view, attached to epandrium by a membrane.

Female. Body length 2.7-3.0 mm, wing length 2.5-2.6 × width 0.9-1.0 mm. Similar to male, but face wider (width slightly less than width of first flagellomere); antenna (Fig. 14D ) shorter, ovoid with pointed apex; arista-like stylus longer than first flagellomere; wing without maculation, but some specimens with hint of brown clouding at and just behind apex of R4+5.

Etymology.

This species is named in honor of LaDonna Ivie (Bozeman, MT) whose hard work and expertise made the Montserrat biodiversity project possible. She ran many traps on Montserrat and the Malaise trap on Dominica that collected the only known specimen of this genus/species from that island.

Distribution.

Dominica, Montserrat, Nevis, St. Kitts.

Remarks.

This is the first report of the genus Systenus in the Lesser Antilles and is the 23rd species described from the New World. Systenus ladonnae is similar to S. maculipennis Bickel from Costa Rica (Bickel, 2015), but S. maculipennis differs most notably in the shape of the wing apex (wing membrane is reduced posteriad of distal vein M in S. maculipennis ) and in lacking a white spot on wing. Systenus ladonnae also resembles the Nearctic S. apicalis Wirth which also has a white and black spot near wing apex, but in S. apicalis the white spot is apical to the brown spot.

Specimens were collected in dry forests near the coast and low elevation mesic forests.

Figures

Figure 14. Systenus ladonnae sp. nov. A habitus of male holotype, left lateral B male wing, dorsal C male antenna, left lateral D female antenna, left lateral. Scale bars: 1.0 mm (A, B), 0.5 mm (C, D).

Figure 15. Systenus ladonnae sp. nov. male terminalia, left lateral. Abbreviations: epand-epandrium; hypand-hypandrium; T-tergite; S-sernite. Scale bar: 0.5 mm.