Chrysotus antillensis sp. nov.

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

Chrysotus antillensis sp. nov. Figs 20 , 21

Type material.

Holotype, ♂ labelled: "DOMINCA: St. John Par./ Cabrits N.P. (Malaise)/ East Cabrits Trail/ 15.58564N, 61.47210W/ 30MAY-07JUNE 2011/ M.A. & L.L. Ivie"; "HOLOTYPE/ ♂ Chrysotus / antillensis / Runyon [red label]" (USNM, type number USNMENT01350612). Paratypes: 41 ♂, 1 ♀, same data as holotype. Montserrat: 1 ♂, Woodlands, Riverside House, 10-12 January 2002, Malaise trap, Ivie, Marske, Puliafico. Nevis: 6 ♂, 2 ♀, Recreation ground, 134 m, 17°07.507'N, 62°34.446'W, 31 August 2017, fogging; 1 ♂, St. John Parish, small pond, 200 m, 17°07.460'N, 62°35.584'W, 26 May 2017, J.B. Runyon. St. Lucia: 5 ♂, 2 ♀, near Micoud, trail to Fond Bay, 15 m, 13°49'48"N, 60°53'42"W, 16-22 May 2009, Malaise trap, S.D. Gaimari & A.R. Cline; 1 ♂, Grande Anse, 38 m, 14.00519N, 60.89737W, Malaise trap, 13-23 May 2009, R. Winton & E. Ivie; 1 ♂, Grande Anse, 14.00529N, 60.89737W, FIT, 23-26 May 2009, C.A. Maier & R.C. Winton (MTEC, USNM).

Other material examined.

British Virgin Islands: 1 ♂, 9 ♀, Tortola, 425 m, 18°25.35'N, 64°38.67'W, 6 November 2016, J.B. Runyon; 1 ♀, Eustatia Island, Baby Beach, 18°30.64'N, 64°21.57'W, 28 October 2016, J.B. Runyon; 1 ♂, 1 ♀, Guana Island, sand pit Malaise, 15-21 October 2001, B. & B. Valentine.

Description.

Male (Fig. 20A ). Body length 1.9-2.1 mm, wing length 1.6-1.7 × width 0.6-0.7 mm. Head: Eyes contiguous below, with anterior ommatidia enlarged; upper face narrowly triangular, metallic green with dense light brown pruinosity. Frons metallic green-blue with sparse light brown pruinosity and minor bronze reflections. Postcranium with dense light brown pruinosity. Palpus small, oval, yellow, covered with minute yellow hairs and a pale brown to black dorsal subapical seta. Proboscis dark yellow to brown with fine pale to brown hairs along margin. Antenna (Fig. 20B ) black; scape rather long, cylindrical; pedicel shorter than scape, with apical ring of small setae, and a larger apical seta dorsally; first flagellomere subtriangular, rounded dorsally at base and overlapping pedicel, width subequal to length; arista-like stylus subapical, inserted just lateral and dorsal to apex in a small notch. Postocular setae white. Thorax: Scutum and scutellum metallic green with strong bronze reflections and sparse light brown pruinosity; postpronotal lobe with a small yellow spot at lateral corner; eight pairs of small biseriate acrostichal setae; six pairs of dorsocentral setae, anterior-most pair small; scutellum with one pair of large marginal setae and one pair of small lateral setae. Pleuron metallic bluish green with dense gray pruinosity; one or two pale brown setae on lower proepisternum. Legs: Coxa I yellow but usually brownish at very base, with yellow-brown to black setae; coxae II and III nearly concolorous with pleuron but with brown tinge and yellow tips, with pale brown to brown setae. Femora yellow except femur III (Fig. 20C ) brown on approximately apical one-third with tip narrowly yellow and with 2-3 distinct av setae near tip; femur II with preapical av and pv seta. Tibia I yellow with small ad seta at 1/4; tibia II yellow with large ad seta near 1/5 and usually a smaller ad seta at 1/2, small pv seta just before 1/5 and 1/2, and with apical ring of four or five setae; tibia III yellow with ad seta at 1/5 and 1/2, a subapical dorsal seta, with pv seta near 1/5, 2/5, 1/2, and 4/5. Tarsi yellow, distal tarsomeres becoming brown, with small claws and very small pulvilli. Ratios of tibia:tarsomeres: leg I: 22-12-5-4-3-4; leg II: 28-13-6-5-3-3; leg III: 34-10-8-5-3-3. Wing: Hyaline, oblong-elliptical, relatively narrow with poorly developed anal lobe. Vein R4+5 and M1 nearly straight but very slightly diverging near apex. Crossvein dm-cu placed near 2/5 of wing length, ca. one-fourth as long as last part of CuA1. Calypter white with white to pale-brown setae. Halter stem and knob yellow. Abdomen: Cylindrical, gradually tapering, with hairs and setae black. Tergites dark metallic green with bronze reflections and little to no pruinosity; tergite VI with numerous small setae. Sternite VIII covering hypopygial foramen, with small setae. Hypopygium (Fig. 21 ) small, partially embedded in tip of abdomen. Hypopygial foramen left lateral. Epandrium dark brown, rounded with distal margin rather flattened, with broad ventroapical lobe bearing three small setae. Surstylus paddle-shaped, shining brown, with three small medial setae near apex and a larger medial black spine-like seta at apex. Cercus brown, triangular with ventral margin rather straight, with brown hairs and setae. Phallus narrow with rounded, very slightly broadened apex; encircled by external membranous sheath that has small wing-like inflations before apex of phallus. Postgonites covered with microtrichia apically. Hypandrial apodemes short, rather pointed apically in lateral view.

Female. Body length 2.1-2.3 mm, wing length 1.9-2.0 × width 0.8-0.9 mm. Similar to male, but face wide (>half width of frons at ocellus) and nearly parallel-sided, covered with dense light gray-brown pruinosity; clypeus distinct, bulging at suture; frons metallic blue-green to violet with very sparse light brown pruinosity; palpi larger, yellow with base brown, covered with yellow microtrichia and a few small brown to black setae; scape short, subequal in length to pedicel; first flagellomere shorter, reniform; abdomen broader, slightly flattened dorsoventrally; wing noticeably broader.

Etymology.

This species is named for the Greater and Lesser Antilles.

Distribution.

British Virgin Islands, Dominica, Montserrat, Nevis, St. Lucia.

Remarks.

The combination of hind femur color and shape of the male first flagellomere of C. antillensis is distinctive (Fig. 20 ). Females are very similar to those of C. hirsutus Aldrich, but females of C. antillensis have two or three small but distinct ventral setae on tibia III (no outstanding ventral setae in C. hirsutus ). Given the number of specimens collected in Dominica in 2011, it is perhaps surprising that C. antillensis was not discovered during the Bredin-Archbold-Smihsonian survey of Dominica ( Robinson 1975). However, four species found on Montserrat that were not included in Robinson (1975) are herein reported from Dominica ( Chrysotus antillensis , C. callichromoides , Systenus ladonnae , and Thrypticus mediofuscus ). These four species appear largely restricted to dry forests at lower elevations, suggesting that this habitat type may not have received adequate attention during the Dominica survey.

Figures

Figure 20. Chrysotus antillensis sp. nov., male A habitus of male holotype, left lateral B antenna, left lateral C femur III, anterior. Scale bars: 1.0 mm (A), 0.25 mm (B), 0.5 mm (C).

Figure 21. Chrysotus antillensis sp. nov. male terminalia, left lateral. Abbreviations: epand-epandrium; ep lobe-epandrial lobe; hypand ap-hypandrial apodeme; pgon-postgonite. Scale bar: 0.1 mm.