Asyndetus fratellus Aldrich, 1896

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

Asyndetus fratellus Aldrich Fig. 19

Asyndetus fratellus Aldrich, 1896: 332.

Material examined.

Lectotype (designated here to fix identity of the species) ♂, St. Vincent, W. Indies, Collection J.M. Aldrich, Asyndetus fratellus Type Ald., "LECTOTYPE/ ♂ Asyndetus / fratellus Aldrich/ des. JB Runyon" [red label] (USNM, specimen number USNMENT01519227). British Virgin Islands: 1 ♂, 1 ♀, Guana Island, sand pit Malaise, 15-21 October 2001, B. & B. Valentine; 3 ♀, same as previous, Malaise, 23-25 October 2000; 1 ♂, same as previous, East end, white beach, 2-10 October 2002, R.R. Snelling; 4 ♂, 2 ♀, Eustatia Island, Main Beach, pan traps, 18°30.59'N, 64°21.41'W, 31 October 2016, J.B. Runyon; 2 ♂, 2 ♀, same as previous, Baby Beach, 18°30.63'N, 64°21.57'W, 28-30 October 2016; Prickly Pear Island, salt pond edge, pan traps, 18°30.18'N, 64°21.99'W, 3 November 2016, J.B. Runyon; 7 ♂, 2 ♀, Virgin Gorda, Bitter End Yacht Club, sandy ground near beach, 18°30.13'N, 64°21.30'W, 8-10 November 2016, J.B. Runyon. Montserrat: 1 ♂, Woodlands Beach, 16°45.75'N, 62°13.42'W, 21 June 2017, J.B. Runyon; 4 ♂, 6 ♀, Old Road Bay (beach), 16°44.623'N, 62°14.035'W, 22 June 2017, J.B. Runyon; 2 ♂, 2 ♀, Fox’s Bay Beach, 16°43.59'N, 62°14.17'W, 24 June 2017, J.B. Runyon; 1 ♀, Rendezvous Bay Beach, 16°48.489'N, 62°12.296'W, 23 June 2017, J.B. Runyon; 1 ♀, Rendezvous Bay, 26 July 2005, yellow pan trap, V.G. Martinson. Nevis: 14 ♂, 17 ♀, Winward Beach, 17°06.96'N, 62°32.91'W, 28 May 2017, J.B. Runyon. Puerto Rico: 2 ♂, 5 ♀, Culebra, Flamenco Beach, 27 December 2001, M. Huben. St. Kitts: 4 ♂, 3♀, Majors Bay, on Ipomoea , 17°13.624'N, 62°38.908'W, 21 May 2017, J.B. Runyon; 1 ♂, 2 ♀, North Friar’s Bay, 17°16.59'N, 62°40.33'W, 24 May 2017, J.B. Runyon; 1 ♂, South Frigate Bay, 17°16.869'N, 62°41.201'W, 24 May 2017, J.B. Runyon. St. Lucia: 18 ♂, 26 ♀, Savannes, Mangrove Reserve, 0-5 m, 13°45.97'N, 60°54.88'W, 3 May 2009, J.B. Runyon; 5 ♂, 5 ♀, Micoud District, Fond Bay at beach, 0-5 m, 13°49.89'N, 60°53.65'W, 8 May 2009, J.B. Runyon (MTEC, USNM).

Re-description, based on material from Montserrat.

Male. Body length 2.2-2.7 mm (body size of some specimens from St. Kitts and Nevis approach 3.5 mm), wing length 1.7-2.1 × width 0.7-1.0 mm. Head: Face as wide as frons, parallel-sided, slightly higher than wide, covered with dense white pruinosity that obscures ground color. Frons with dense grayish white pruinosity, obscuring ground color; vertical setae proclinate. Palpus black with sparse white pruinosity, with black setae, a couple larger setae near apex. Proboscis black. Antenna black; pedicel somewhat produced above and on sides; first flagellomere short, wider than long, rounded apically; arista-like stylus inserted near middle of dorsal edge. Lower postocular setae white. Thorax: Scutum dark metallic green-blue with dense white pruinosity, with distinct band of coppery brown pruinosity between dorsocentral rows becoming slightly broader posteriorly and ending at scutellum and coppery brown pruinose area above wing bases; 1-6 pairs of irregularly biseriate acrostichal setae, often missing on anterior half of scutum; five pairs of dorsocentral setae; scutellum with one pair of large marginal setae and one pair of small lateral setae. Pleuron dark metallic bluish green with dense grayish white pruinosity; with two small black setae on lower proepisternum and one or two small black setae on upper proepisternum. Legs: Hairs and setae mostly black. Coxae concolorous with pleuron; coxae I and II with black setae anteriorly; coxa III with black lateral seta near base and small brown lateral seta near 2/3. Femora dark brown to black with extreme tips yellow, with av and pv rows of longer rather slender dark setae ventrally (longest ca. half width of femur) that can appear yellowish in certain lights, and with a few stouter av and pv setae near apex; femora II and III also with slightly larger anterior setae near apex. Tibiae I and II yellow (some specimens from British Virgin Islands, Puerto Rico, St. Lucia, and St. Vincent have tibia I and/or II varying degrees of brown), tibia II usually brownish at very base, tibia III brown but sometimes yellowish basally; tibia I with small area of close-set pale setulae av on apical half, with small setae, an ad seta near 1/3, pd seta near 1/3, 1/2, near apex and apical ad, posterior, and pv seta; tibia II with large ad seta near 1/5 and 3/5, large pd seta just before 1/5, 1/2, near 3/5, smaller ventral seta near 3/5, and 3-4 large apical setae, the ventral one largest; tibia III with large setae, ad seta at 1/5, just beyond 1/2 and sometimes smaller seta near 2/5, with five or six pv small setae of varying lengths rather evenly spaced along length of tibia, no ventral setae, four apical setae the dorsal seta largest. Tarsomeres I(1) and II(1) with apex brown, tarsi otherwise dark brown; tarsomere 5 of each leg with apical fan of small black dorsal setae. Tarsomere I(5) slightly broadened. Tarsal claws absent, pulvilli white and enlarged on all legs. Ratios of tibia:tarsomeres: leg I: 32-14-8-6-4-5; leg II: 40-18-10-7-4-5; leg III: 45-13-12-9-6-5. Wing: Hyaline but with slight whitish sheen and brown veins, oblong-elliptical with prominent anal lobe. Veins R2+3 and R4+5 rather close together, subparallel but slightly diverging apically, both joining costa before wing apex; R4+5 nearly straight to scarcely bent backwards at apex. Distal section of M free and offset from basal section (rarely these sections are indistinctly connected via a thin trace of vein M; basal and distal sections of M overlap in a few female specimens from St. Kitts and Nevis). Crossvein dm-cu placed near basal 1/3 of wing length, ca. one-seventh as long as last part of CuA1. Calypter white with white setae. Halter stem yellow-brown and knob white. Abdomen: Cylindrical, dark metallic green (some specimens with distinct copper reflections) obscured by grayish white pruinosity that is thickest laterally. Tergites covered with numerous small black setae that are longer laterally and along distal margins; tergite VI mostly to completely hidden, bare. Sternites with sparse but rather long setae that can appear brownish. Sternite VIII with four short but stout setae projecting posteriorly from apex of preabdomen. Hypopygium small, dark brown, enclosed in tip of abdomen. Epandrium dark brown, nearly round. Surstylus bilobed; dorsal lobe shining dark brown, as long as epandrium, narrow, broadest basally with slightly expanded apex, with distinct dorsal seta near 2/3 (and sometimes a second smaller neighboring seta) and minute hairs apically; ventral lobe of surstylus half as long as dorsal lobe, subtriangular, with distinct seta at apex subtended by one or two smaller setae and medially near base with a papilla bearing a seta. Cercus dark brown, small, nearly round, covered with small black setae of nearly uniform length.

Female. Body length 2.6-2.9 mm, wing length 2.1-2.4 × width 0.8-1.1 mm. Similar to male, but face slightly wider; clypeus distinct, bulging slightly; femora II and III without longer ventral setae but av row on femur I distinct; tibia III often yellowish on basal half; each tarsomere 5 without fan of black dorsal setae; pulvilli small; short distinct claws present.

Distribution.

British Virgin Islands, Grenada, Jamaica, Montserrat, Nevis, Puerto Rico, St. Kitts, St. Lucia, St. Vincent.

Remarks.

All specimens from Montserrat have yellow tibiae I and II, and because of this I at first suspected these represented an undescribed species. The only other species of Asyndetus known from the West Indies reported to have tibiae I and II yellow is A. syntormoides Wheeler which has an enlarged first flagellomere and vein M delicate but complete throughout ( Wheeler 1899: figs 50-52). However, examination of material from Puerto Rico to St. Lucia (see Material examined) reveals the color of tibiae I and II varies from yellow to dark brown. Specimens from islands north of Montserrat generally have tibia I yellow with tibia II often yellow but frequently brown (a few specimens also have tibia I brown), but specimens southward usually have all tibia brownish, including the lectotype from St. Vincent (Fig. 19 ; a few specimens from St. Lucia have tibia I yellow). Other characters are variable including body size (2.0-3.5 mm), number/extent of acrostichal setae, and size of ventral setae on femora II and III. I can find no characters to reliably distinguish these specimens, and thus consider them conspecific, and interpret A. fratellus as a littoral species widespread in the West Indies. However, a revision of this genus in the Neotropics is needed. Two species similar to A. fratellus were described from Dominica ( A. dominicensis Robinson) and Puerto Rico ( A. deficiens Robinson) that might prove conspecific. Outside the West Indies, A. currani Van Duzee (Panama, photos of holotype examined) is very similar and might also prove conspecific, but the holotype has ventral hairs on femora more yellowish and wing with R4+5 slightly more bent backwards at apex.

Many adults of A. fratellus were collected from leaves of beach morning glory ( Ipomoea pes-caprae ).

Figures

Figure 19. Lectotype male of Asyndetus fratellus (St. Vincent), left lateral (specimen number USNMENT 01519227). Scale bar: 1.0 mm. Photo taken by Alyssa Seemann (USNM).