Scorpiurus aramoana Bickel & Kerr, 2018

Bickel, Daniel J. & Kerr, Douglas Steven, 2018, Scorpiurus aramoana (Diptera: Dolichopodidae), a new species from New Zealand, Zootaxa 4422 (1), pp. 78-84 : 80-84

Scorpiurus aramoana Bickel & Kerr , sp. nov.

( Figs 1–3 )

Material examined. HOLOTYPE ♂: NEW ZEALAND: DN: Aramoana, mouth of Otago Harbour, north of Dunedin , -45.782842 170.702806, 0–5 m, tidal mud/ sand flat, D. S. Kerr ( OMNZ) . PARATYPES: same data as holotype, 1 ♂, 3 ♀, 7 Jan. 2018 ( OMNZ) ; 2 ♂, 2 ♀, 7 Jan. 2018 ( NZAC) ; 2 ♂, ♀, 1 Jan. 2016 ( AMS) ; 1 ♂, 1 ♀, 21 Dec. 2015 ( BPBM) .

Description. Male. Body length 5.0– 5.5 mm; wing length 5.3–5.4, width 1.8 mm. Head. ( Figs 1h, i ); occiput convex; postcranium vertex, frons and upper face dark metallic green with blue-violet reflections, and covered with grey pruinosity; lower face and clypeus covered with dense golden pruinosity; frons wide, pair of strong white incurved postvertical setae present on dorsal postcranium; with row short white setae extending laterally from dorsal postcranial setae to orbit; three black orbital setae near vertex, with reminder of orbital setae white; ventral three-quarters of postcranium covered with field of white setae; ocellar tubercle distinct with pair strong diverging black ocellar setae; vertical setae strong black, subequal in length to ocellars; face narrowed ventrad of antennal bases but expanded towards clypeal margin; eyes with facets uniform, with tiny microtrichia between facets; palpus covered with dense golden pruinosity and with numerous cream-colored setae; proboscis dark brown; antenna black; scape longer than pedicel; pedicel without subapical ring of short setae; postpedicel rounded subtriangular and tapering to point with some setulae at midlength; arista apical, slightly more than twice length of postpedicel. Thorax. ( Fig. 1a ); metallic green with bronze reflections in ground color, covered with light grey pruinosity, with dense pruinosity on pleura; setae black; acrostichal setae regularly biseriate, with 13–14 pairs, and expanding laterally before reaching posterior mesonotal slope, but not reaching scutellum, i.e., with bare space anteriad of scutellar suture; some 11–12 dorsocentral setae, posterior setae strong, and anterior dc short, and with some short supernumerary setae laterad of anterior dc and anteriad of mesonotal suture; 1 posthumeral, 1 presutural, 1 sutural, 1 postsutural, 1 supra-alar, and 1 postalar setae; 2 notopleural setae; scutellum with pair of strong median setae and pair of strong lateral setae; proepisternum with group of 6–7 weak dorsal white setae and group of 10–12 stronger ventral white setae. Legs. ( Figs 1c, d, e ); coxae and femora dark metallic blue-green but femora with apical fifth yellow, and covered with dense grey pruinosity; tibiae and tarsi mostly yellow and with darker infuscation and with dusting of silvery pruinosity, and as noted in the descriptions below; anterior surface of coxa I covered with dense whitish setae; coxa II with strong white anterolateral seta and white anterior hairs; coxa III with strong white lateral seta subtended by weaker hairs; I: 6.2; 5.0; 3.1/1.0/ 0.9/0.8/1.2; femur I with scattered white setae and with some longer dorsal setae, and 2 white subapical pv setae; tibia I with anterior row of short hairs along length, with short black ad setae at 1/4 and 2/5, with row of short black pd setae along length, with longer setae near 1/4, 2/5, 3/4 and 7/8; all tarsomeres dorsoventrally flattened and distally expanded, subtriangular, with yellow ground color and infuscated margins, with black vestiture, and covered with orientated silvery pruinosity (MSSC); tarsus I with tarsomeres 1–4 each with posterior apicoventral black spatulate seta (MSSC), and tarsomeres 2–4 each with anterior apicoventral blade-like seta; claws paired and pulvilli grey; II: 7.0; 7.1; 3.0/1.0/ 0.9/0.6/1.0; femur II with scattered white hairs, without major setae; tibia II with ad near 1/4, 1/2, pd at 1/4 and 3/5, and subapical corona of pd, ad, anterior, ventral (longer) and pv setae; tarsus II with tarsomeres 2–5 dorsoventrally flattened, with dense silvery pruinosity on dorsal surface; each tarsomere 2–4 bordered with row of short black anterior and posterior setae, and each with short anterior and posterior apicoventral spine-like seta; claws paired and pulvilli grey; III: 9.2; 10.4; 2.9/2.0/1.2/0.8/1.1; femur III with scattered white setae, without stronger setae; tibia III with some scattered short black setae, and with short ad setae at 1/6, 1/4 and 3/5, stronger pd setae at 1/4 and 1/2 with posterior row along length of some 16–18 erect white hairs, and with subapical corona of black pd (longest), ad, anterior and ventral setae; tarsus III yellow with grey pruinosity, and row of short black setulae. Wing. ( Fig. 1b ); elongate with grey translucent membrane; R 1 joining costa near 2/5; R 2+3 joining costa near 9/10; R 4+ 5 in gentle curve to join costa just anteriad of apex, vein M beyond dm-cu cross vein slightly bowed with respect to R 4+5, but subapically curved and veins subparallel before apex; CuAx ratio 0.9; lower calypter mostly yellow with fan of pale yellow setae; halter with brownish stalk and pale yellow club. Abdomen. ( Figs 1c, f, g ); dorsoventrally flattened; tergites with metallic green ground color covered with dense grey pruinosity and short white setae; posterior abdominal segments bent dorsally and hypopygium directed ventrally; sternite 8 with dense grey pruinosity and field of short white setae, and positioned left basally over hypopygium; epandrium massive and spheroidal, and covered with grey pruinosity; surstyli shining black and plate-like with pointed ventral and tapering curved apical projections; cercus yellow with scattered whitish hairs, elongate and band-like, almost as long as abdomen, and carried rolled up under abdomen at rest; base of cercus with prominent rounded mound bearing numerous translucent capitate setae. Female. Similar to male except as noted ( Figs 2a, b ): body length longer, 5.5–6.5 mm; wing longer 6.2–6.4 mm, width 1.9 mm; also with golden pruinosity on clypeus and palpus; leg coloration with similar; I: 6.0; 5.0; 2.4/1.2/0.8/0.6/1.0; tarsus I with tarsomeres unmodified; II: 7.0; 7.2; 3.4/1.5/ 0.8/0.6/1.1; tarsus II with tarsomeres unmodified; III: 10.2; 10.0; 2.8/1.8/1.2/1.0/1.2; distal tergite 5 with numerous strong black posteriorly-directed setae; tergite 10 medially split with apical row of four short spatulate setae or acanthophorites on each tergite half; cerci positioned medially, short, digitiform and blade-like, without setation.

Remarks. Scorpiurus aramoana is a striking species with flattened male foretarsi covered in orientated silvery pruinosity, and reflecting light depending on the angle of view. These modifications are undoubtedly used in mate recognition during courtship. Here it is worth noting another New Zealand hydrophorine, Helichochaetus discifer Parent (see Key), whose males have similar flattened foretarsi, also covered with silvery pruinosity (http:// naturewatch.org.nz/observations/4765496). This suggests similar selective pressures and morphological potential within the subfamily. Also related to mating behavior is the larger size of females with respect to males. This is found in other hydrophorine genera, such as the genus Hydrophorus , where mate guarding, the male clinging on the back of the female after mating, is well known ( Dyte 1988) (http://naturewatch.org.nz/observations/4960446). The female oviscapt of S. aramoana has short spatulate setae or acanthophorites on each half of tergite 10, presumably for digging to oviposit in the sandy mud substrate. The field of strong black posteriorly directed setae on tergite 5 may assist in the oviposition process ( Fig. 2b ).

The type series of Scorpiurus aramoana was collected on exposed and rather sandy mud flats during low tide at Aramoana, north of Dunedin ( Figs 2e, f ). Large numbers of both sexes were seen on the mudflats during the months of December and January. When approached or disturbed they would take to the air and fly low to the ground for a short distance (usually less than a metre) before settling again. Individuals were observed on the flats feeding on small amphipods ( Figs 2c, d ; observations, DSK). (see also http://naturewatch.org.nz/observations/ 2499715, http://naturewatch.org.nz/observations/2487673, http://naturewatch.org.nz/observations/2549641, http:// naturewatch.org.nz/observations/9466492, & http://naturewatch.org.nz/observations/9466529). In addition to the type series collected at Aramoana, DSK also observed this species in numbers on a sandy estuarine mudflat some 134 km southwest of Dunedin (SL: Tahakopa River, Papatowai, 12 March 2018).

Etymology. The specific epithet aramoana is an indigenous Maori place name and regarded as a noun in apposition.

Figures

FIGURE 1. Scorpiurus aramoana sp. nov.: a. male head and thorax, dorsal view; b. male wing, dorsal view; c. male habitus, ventral view; d. male anterior habitus, right ventral view; e. male left tarsus I, dorsal view; f. cleared male postabdomen (left surstylus removed), left lateral view; g. male postabdomen, left lateral view; h. male head, anterior; i. male head and thorax, right anterior view. Scale bar in mm.

FIGURE 2. Scorpiurus aramoana sp. nov.: a. female habitus, left lateral; b. female abdomen and legs, ventral; c. female on tidal flat substrate; d. female with amphipod prey in proboscis; e, f. Aramoana tidal flats, mouth of Otago Harbour, north of Dunedin, New Zealand, the type locality.

FIGURE 3. Map of New Zealand showing known collecting locales of Scorpiurus species.