Setostylus tridigitus Qi, Huang et Wang, 2022

Qi, Lei, Huang, Junhao, Wu, Hong & Wang, Qingyun, 2022, Two new species of Setostylus Matile, 1990 (Diptera: Keroplatidae) from China, Zootaxa 5165 (3), pp. 443-450 : 444-446

Setostylus tridigitus Qi, Huang et Wang sp. n.

( Figs 1–2 )

Diagnosis. This new species resembles S. abdominalis (Sasakawa & Tamu) in wing pattern and general appearance of the male terminalia, but it differs from the latter in the subtriangular terminal flagellomere in the male antennae, and gonocoxites having 18–20 black strong spines on each posteromesal lobiform part in the male terminalia. In S. abdominalis , the terminal flagellomere is suboval in the male antennae, and the gonocoxites have 23–25 short spines on each posteromesal lobiform part in the male terminalia.

Type material. Holotype. Male, CHINA: Guangdong, Mt. Dinghu (23.92° N, 112.32° E), 72 m, 27.VIII.2020, coll. Lei Qi, slide no. DHS-8-85 . Paratypes. Male, CHINA: Guizhou, Mt. Leigong (26.36° N, 108.16° E), 3.X.2019, coll. Changlie Yang, slide no. LGS-10-42; male, Guangdong, Chebaling National Nature Reserve (24.42° N, 114.15° E), 378 m, 12.VI.2020, coll. Lei Qi, slide no. CBL-8-39; male, Guangxi, Dayaoshan National Nature Reserve (24.14° N, 110.19° E), 1,520 m, 8.VI.2020, coll. Tao Li, slide no. DYS-10-70 .

DNA barcode. The DNA barcode sequence from holotype and paratypes are deposited in BOLD (https://boldsystems.org/) and GenBank (https://www.ncbi.nlm.nih.gov/), with the BIN number of AEI9998 and the GenBank accession number of ON190026 .

Description. Male ( Fig. 1 ). Body length (without antennae) 4.5 mm. Wing length 1.3 mm, width 2.8 mm.

Head ( Fig. 2a ) dark brown, with width 1.3 times of its height. Vertex with abundant dark setae, frons and face bare. Three ocelli arranged nearly in a line, lateral ocelli about three times of median one in diameter. Compound eyes almost hemispheric, covered with pointed setae. Clypeus brown with about 25–30 dark brown setae. Mouthparts reduced, maxillary palpus with two segments; segment 2 erecting forward, oval, with 6–8 setae laterally. Antenna ( Fig. 2c ) brown and strongly compressed; scape and pedicel funnel-shaped, covered with several subapical and apical setae; flagellum pectinate and 14-segmented, each flagellomere bearing 6–10 setae on dorsal edge, segments 1–8 with a few microtrichia ventrally, subtriangular apically.

Thorax ( Figs 2d–e ) brown. Scutum brown, covered with bushy setae, three dark brown longitudinal stripes. Scutellum brown, with several setae. Mediotergite brown, bare. Anepisternum dark brown, subtriangular, with thick setae on top corner. Laterotergite pale brown and subelliptical, bare. Halter length 0.8 mm, stem translucent, bare; knob dark brown, bearing setae.

Wing ( Fig. 2b ) brown, without pattern, veins distinct. Wing membrane covered with abundant brown microsetae. Wing margin with short brown setae. R 1 and R 4+5 with setae arranged along the veins. Vein C terminates at 1/2 of R 4+5 to M 1. Vein m-cu and R+M fusion subequal in length; Rs about twice length of m-cu. Vein M 1 and M 2 weaker than other veins. CuA slightly curved; CuP free terminally, approximates outer margin.

Legs ( Fig. 1 ) brown to dark brown. Fore coxa brown, covered with dense setae. Mid and hind coxae pale brown and bare on basal 2/3, dark brown and setose on distal 1/3. Femur, tibia and tarsus brown, covered with numerous setae. Hind tibia with two separated combs apically.

Abdomen ( Fig. 1 ) brown to dark brown, with tergite 1 brown, tergites 2–4 pale and 5-8 dark brown, covered with dense dark setae.

Terminalia ( Figs 2f–h ) brown. Tergite 9 subpentagonal, with abundant setae. Gonostylus curved, narrowed gradually towards end; basal 2/3 covered with setae, 10–12 black spines on inner margin, and having a tiny projection distal-laterally; apical process bare and subtransparent, slightly raised at half of inner margin, with a dark brown bristle terminally, hyaline part about 1.5 times length of bristle. Gonocoxites brown, with narrow incision at middle posteriorly, bearing 18–20 black strong spines on each posteromesal lobiform part. Cercus pale brown, digitate, with numerous setae.

Female. Unknown.

Etymology. The name of this new species comes from the Latin tri (three) and digitus (finger), which refers to the three-toed streak on the scutum.

Figures

FIGURE 1. Setostylus tridigitus sp. n., holotype, male, lateral view.

FIGURE 2. Setostylus tridigitus sp. n., holotype. a. head (frontal view), antennae removed; b. wing; c. antenna; d–e. thorax (d. lateral view; e. dorsal view); f–h. terminalia (f. vertral view, with a close-up of gonostylus in the upper right; g. dorsal view; h. lateral view). Slide No. DHS-8-85.