Scorpiurus aenescens Parent, 1933

Masunaga, Kazuhiro, 2017, Saltmarsh flies of the genus Scorpiurus Parent from New Zealand (Insecta: Diptera: Dolichopodidae), Zootaxa 4324 (3), pp. 581-591 : 585-587

Scorpiurus aenescens Parent

( Figs 3A , 4A–B , 5 , 6 )

Scorpiurus aenescens Parent, 1932: 161 (nomen nudum). Scorpiurus aenescens, 1933: 358 .

Diagnosis. Large-sized species of 4.0– 5.3 mm in body length with 1 st flagellomere 2.2 times as long as its basal thickness, proboscis 0.7 times as long as eye height, acrostichal setae continuing onto flat part of scutum in front of scutellum, scutellum with 4 long setae, apical parts of femora and tibiae pale brown, male posterior abdominal segments bent dorsally and hypopygium directed ventrally.

Description. Male ( Fig. 3A ). Head 1.8 times as high as long, as wide as high. Frons wide, metallic green with grayish pollinosity; frontal bristle as long as ocellar bristle. Ocellar tubercle distinct, with 2 strong ocellar bristles and 2 minute postocellar setae. Occiput metallic green with grayish pollinosity. Postocular ciliation uniserial, erect, black. Postgena with dense array of many long, white setae. Face and palpus brown with dense grayish pollinosity, tinged with green. Face at narrowest part 0.1 times as wide as head. Palpus 2.7 times as long as wide, clothed with black setae. Proboscis 0.7 times as long as eye height. Antenna black; scape 1.3 times as long as deep; pedicel as long as deep; 1 st flagellomere 2.2 times as long as basal thickness, with some setulae at midlength; arista apical, 1.4 times as long as 1 st flagellomere . Thorax. Mesonotum metallic green in ground color, with grayish white pollinosity. Thoracic bristles black. Chaetotaxy: acrostichals well developed, biserial, 11–23 in each row; dorsocentrals (dc) biserial, with 7 long setae in each row, and 0–5 supplementary short setae anterior to 1st dc, 7th dc longest; postpronotum with 1 long seta and 1–5 short setae; 1 each present of posthumeral, presutural, sutural, postsutural, supra-alar and postalar setae; notopleuron with 2 setae. Proepisternum with 8–11 long white setae each on upper and lower parts. Scutellum with 2 pairs of strong marginal bristles. Legs. Coxae and femora concolorous with pleura. Apical portions of femora and tibiae pale brown. Basal portion of middle and hind tarsomeres pale brown, but fore tarsomeres, apical 1/4 of mid tarsomere 1, apical 1/2 of tarsomere 2, tarsomeres 3–5, apical 1/3 of hind first tarsomere, apical 1/2 of tarsomeres 2–4 and tarsomere 5 dark brown. Foreleg. Coxa 2.8 times as long as thick, with dense array of many long, white setae on anterior surface, and conspicuous black bristle on anterior apical margin. Femur 5.6 times as long as thick, 1.1 times as long as tibia, tapered gradually toward apical 2/3, with long, erect anterodorsal seta on subapex, row of long anteroventral setae, 2–3 long, posteroventral setae on subapex, row of long posterior setae, and row of posterodorsal setae, 3 of which strong, erect and narrowly-spaced. Tibia 2.0 times as long as fore first tarsomere, with 1 erect dorsal seta on basal 1/3; row of long anterodorsal setae, 1–2 of which particularly thick, near base; 2 long ventral setae on apical 1/3 and apical 1/4, respectively; row of posterodorsal setae, 5–6 of which long, strong, erect and narrowly-spaced. Tarsomeres simple, relative lengths of tarsomeres 1–5 26:21:16:9:10. Midleg. Coxa with row of long, white setae on anterior surface and conspicuous strong, black seta near base. Femur as long as tibia, ventral surface of femur slightly sinuate ventrally, weakly swollen on ventral portion, and curved dorsally at middle, and with strong anterior subapical seta, several short, thick ventral setae clustered near base and midlength, one strong posterior subapical seta, and 2–4 strong posteroventral setae near tip. First tarsomere with ventral surface curved dorsally in basal 1/3 and curved ventrally at midlength widest in basal half 1.5 times as wide there as at narrowest part in basal 1/5; relative lengths of tarsomeres 1–5 33:17:13:8:10. Hindleg. Coxa with conspicuous outer seta on basal 1/3, some white setae on outer surface, and several long, white setae on apical margin. Trochanter with long ventral setae. Femur 0.9 times as long as tibia, with 2 strong dorsal setae at apical 1/5 and apical 1/3 respectively, and row of strong ventral seta at midlength. Tibia with 3–5 strong rows of antero- and posterodorsal setae and circlet of strong apical setae, of which posterodorsal one longest. Tarsomeres simple, their relative lengths 25:19:15:10:10. Wing ( Fig. 4A ). Long, narrow and darkened. Apical section of CuA1 1.4 times as long as crossvein dm-cu. Calypter pale brown with pale brown fringe. Halter yellowish brown. Abdomen. Abdominal terga tinged green with grayish pollinosity and black setae; posterior abdominal segments bent dorsally and hypopygium directed ventrally. Anteroventral corners of tergum 5 digitiform strongly curving anteriorly. Hypopygium large and rounded. Cercus long and tapered; dorsal margin curving ventrally, with long, white, curved setae on ventral margin ( Figs 5–6 ). Body length 4.1–5.3 mm; wing length 4.1–4.7 mm.

Female. Face at narrowest part 0.2 times as wide as head. Proboscis 0.7 times as long as eye height. Relative lengths of tarsomeres 1–5 of foreleg 37:14:10:7:10, those of midleg 30:21:8:6:10, and those of hindleg 25:18:13:9:10. Wing: apical section of CuA1 1.2 times as long as crossvein dm-cu ( Fig. 4B ). Body length 4.0– 4.8 mm; wing length 4.7–5.2 mm.

Material examined. New Zealand: 1♀, fly emerging from pupal case in mud of tidal mudflats, upper reaches Manukau Hbr., 1.xi.1952, K.T. Wise Coll. ( NZAC); 7♂, 2♀, swept x reeds, south side upper reaches, Manukau Hbr. , 2.xi.1952, K.T. Wise Coll. ( NZAC); 2♂, 4♀, Te Atatu Peninsula , Auckland, North Island , 30.xi.2007, K. Masunaga leg. ( NZAC, LBM); 13♂, 13♀, Te Atatu Peninsula , Auckland, North Island , 1.xii.2007, K. Masunaga leg. ( NZAC, LBM); 73♂, 271♀ , 3 km W of Linkwater, South Island , 6.xii.2007, K. Masunaga leg. ( NZAC, LBM); 126♂, 108♀ , 3 km W of Linkwater, South Island , 7.xii.2007, K. Masunaga leg. ( NZAC, LBM).

Type locality: Nelson, South Is. , New Zealand.

Distribution: New Zealand (North Is., South Is.) ( Fig. 1 )

Remarks. Externally, this species is similar to Scorpiurus thorpei sp. nov., but S. aenescens differs from those of the new species in having acrostichal setae on the flat area in front of the scutellum, its femora concolorous with the pleura except for their apical parts and, in the male dorsally bent posterior abdominal segments and a ventrally directed hypopygium.

Adults fly very quickly near the ground, so it is difficult to catch in the open with a net. The inlet at my main survey site near Linkwater, South Island, has wide tidal flats covered with short reeds ( Fig. 2A–B ). By sweeping the reeds on which the flies were resting with a butterfly net, I was able to catch many of them.

Figures

FIGURE 1. Map of sampling sites.

FIGURE 2. Habitat of the genus Scorpiurus. A, Landscape of the sampling site. Near Linkwater, South Island, New Zealand; B, Enlarged view of habitat.

FIGURE 3. Adult males of Scorpiurus spp. A, S. aenescens; B, S. thorpei sp. nov.

FIGURE 4. Wings of Scorpiurus spp. A, S. aenescens ♂; B, S. aenescens ♀; C, S. thorpei sp. nov. ♂; D, S. thorpei sp. nov. ♀. Scale bars = 1 mm.

FIGURE 5. Scorpiurus aenescens, male. Postabdomen in lateral view. Scale bar = 1 mm.

FIGURE 6. Scorpiurus aenescens, male. Hypopygium in lateral view. Scale bar = 1 mm.