Chrysotus montserratensis, Runyon, 2020

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

Chrysotus montserratensis sp. nov. Figs 27 , 28 , 29

Type material.

Holotype, ♂ labelled: "WEST INDIES: MONTSERRAT/ Big River 450 m/ 16°45.690'N, 62°11.174'W / 28 JUNE 2017, JB Runyon"; "HOLOTYPE/ ♂ Chrysotus / montserratensis / Runyon [red label]" (USNM, type number USNMENT01350614). Paratypes: Montserrat: 3 ♀, same data as holotype; 2 ♀, Big River, 5 August 2005, yellow pans, V.G. Martinson; 2 ♀, Jack Boy Hill (top), 480 m, 16°45.797'N, 62°10.886'W, 25 June 2017, J.B. Runyon; 1 ♀, ghaut above Montserrat Volcano Observatory, 330 m, 16°45.130'N, 62°12.487'W, 27 June 2017, J.B. Runyon; 1 ♂, Bottomless Ghaut, 400 m, 16°45.994'N, 62°11.497'W, 28 June 2017, J.B. Runyon; 1 ♀, Katy Hill (top), 730 m, 16°45.731'N, 62°11.646'W, 28 June 2017, J.B. Runyon (MTEC, USNM).

Description.

Male (Fig. 27A ). Body length 2.9-3.0 mm, wing length 2.4-2.5 × width 0.9-1.0 mm. Head: Eyes essentially contiguous below; face dark metallic green-blue obscured by light brown pruinosity, lower half of face very narrow (subequal in width to one ommatidium) and nearly parallel-sided, upper face narrow triangular. Frons metallic green-blue with brown pruinosity. Palpus brown, subquadrate with rounded corners, with ca. four rather large black setae (longest subequal to width of palpus). Proboscis dark brown, somewhat enlarged and projecting anteriorly, with brown hairs along margin. Antenna (Fig. 27A ) black; first flagellomere large, triangular-ovate to crescent-shaped, base extending above and overlapping pedicel; arista-like stylus subapical, inserted in shallow notch. Postocular setae brown to black. Thorax: Scutum and scutellum dark metallic green with slight blue reflections and sparse light brown pruinosity; setae on scutum black; six pairs of rather large irregularly biseriate acrostichal setae; six pairs of dorsocentral setae; scutellum with one pair of large marginal setae and one pair of smaller lateral setae (ca. half length of larger setae). Pleuron dark brown to almost black with slight green-blue reflections, obscured by gray pruinosity; with two brown to black setae on lower proepisternum. Legs: Dark brown to black with black setae and hairs. Coxa I with rather long coarse anterior setae becoming larger distally; coxa II apically with two small brown spines composed of fused setae. Trochanter II with large av seta. Femur I with slightly longer pv setae full-length, those at very base erect, those near tip larger. Femur II with slightly longer setae av and pv, with subapical row of four to five posterior setae; femur III with a few larger preapical av, pv, and anterior setae. Tibia I with very small ad seta near 1/4 and larger pd seta at apex, with ventral setae slightly longer; tibia II with large ad seta near 1/4 preceded by very small seta, a smaller ad seta near 1/2, ventrally with a seta near 1/3, 1/2, and 3/5 which increase in size distally, and four large apical setae; tibia III with 3-5 ad setae the largest near 1/5, 2/5, and just beyond 1/2, four or five pd setae with largest near 1/3, 2/5, 3/5, four apical or subapical setae, ventral surface with slightly longer setae. Ventral surface of tarsomeres I(1, 2) with longer setae (longest slightly wider than tarsomere); tarsus III (Fig. 28B ) with dense short brushy setae; tarsomere III(1) a little broadened with longest setae anteriorly; tarsomere III(2) prolonged posteriorly into a spur overlapping ca. half of tarsomere III(3), this spur covered ventrally with short dense setae; tarsomeres III(3, 4) with slightly longer setae anteriorly and dorsally. Pulvilli not enlarged, all legs with two claws. Ratios of tibia:tarsomeres: leg I: 38-22-9-8-6-4; leg II: 40-20-8-7-4-3; leg III: 50-14-6 (12 including spur)-11-8-4. Wing: Hyaline, elliptical, with brown veins. R2+3 straight. R4+5 and M1 nearly parallel in apical half of wing, both curving slightly backward apically. Last part of CuA1 ca. 2.5 × as long as crossvein dm-cu. Calypter dark brown with black setae. Halter knob and stem yellow. Abdomen: Cylindrical, rather broad, gradually tapering, with hairs and setae black. Tergites and sternites dark metallic greenish, nearly black; tergite VI with numerous small setae and larger marginal setae. Sternite VIII with small setae, covering hypopygial foramen. Hypopygium (Fig. 29 ) small, blackish, positioned in ventral notch at tip of abdomen. Epandrium black, with small ventroapical lobe bearing two small setae. Surstylus elongate, shining dark brown, with strong subapical spine and spine at apex, and two small hairs near apex. Cercus elongate triangular, brown, with numerous stiff brown setae especially along dorsal margin; more sclerotized narrowly along ventral edge. Phallus simple, narrow, with apex round; sheath of phallus broadened dorsally near and beyond emergence from epandrium, with three or four small teeth along dorsal margin ca. midway between epandrium and tip of phallus. Postgonites rounded apically with some microtrichia. Hypandrial apodemes long and narrow.

Female. Body length 3.1-3.5 mm, wing length 2.6-3.1 × width 0.9-1.4 mm. Similar to male, but face wide, narrowest part ca. two-thirds width of frons at ocellus; dark metallic green-blue obscured by very sparse light brown pruinosity; clypeus distinct, bulging at suture, slightly widened; palpus broader, more rounded apically, with more setae; first flagellomere (Fig. 27B ) smaller, length two-thirds height, distinctly crescent-shaped in medial view, apical notch smaller; scutum with strong metallic green-blue-violet reflections; coxa II without apical spines; tarsomere II(1) with less distinct ventral setae; tarsus III without dense brushy setae; tarsus III(2) without spur.

Etymology.

This species is named for the island of Montserrat.

Distribution.

Montserrat.

Remarks.

Chrysotus montserratensis is related to C. excisus Aldrich (Dominica, Mexico, St. Vincent) and C. pseudexcisus (Dominica) being most closely related to C. excisus which shares tarsomere III(2) prolonged posteriorly in a spur overlapping base of tarsomere III(3). Chrysotus montserratensis differs in having a larger spur on tarsomere III(2) (Fig. 28 ), larger body size, and a yellow halter knob.

Figures

Figure 27. Chrysotus montserratensis sp. nov. A habitus of holotype male, left lateral B female antenna, left lateral. Scale bars: 1.0 mm (A), 0.5 mm (B).

Figure 28. Tarsus III of males, posterior views A Chrysotus excisus Aldrich (Dominica) B Chrysotus montserratensis sp. nov. Arrows indicate spur-like projection on tarsus III (2). Scale bar: 0.5 mm.

Figure 29. Chrysotus montserratensis sp. nov. male terminalia, left lateral. Abbreviations: epand-epandrium; ep lobe-epandrial lobe; hypand ap-hypandrial apodeme. Scale bar: 0.1 mm.