Hybos serratus Yang & Yang, 1992: 1089
Creators: name: PLANT, ADRIAN R.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Hybotidae
Hybos
Hybos serratus

description: Hybos serratus Yang & Yang
(Figs 3, 141–150, 269, 297)
Hybos serratus Yang & Yang, 1992: 1089.
Material examined. 231♂, 291♀, THAILAND, Chiang Mai Province, Doi Phahompok National Park; Doi Phaluang, 20°1.06'N, 99°9.581'E, 1449 m; Kiewlom 2/ Montane Forest, 20°3.426'N, 99°8.553'E, 2112 m; Kiewlom 1/montane forest, 20°3.549'N, 99°8.552'E, 2174 m; Mae Fang Hotspring, 19°57.961'N, 99°9.355'E, 569 m: Chiang Mai Province, Huai Nam Dang National Park; Thung Buatong View Point, 19°17.56'N, 98°36.029'E; Helipad, 19°18.33'N, 98°36.289'E: Chiang Mai Province, Doi Chiangdao; National Park Headquarters, 19°24.278'N, 98°55.311'E, 449 m; HRD Pakea Stn (evergreen forest and coffee plantation), 1560 m; nr. rd. from Mueang Noi—Wiang Haeng, 98°30.44'N 90°50.17'E, 950 m: Chiang Mai Province, Doi Suthep National Park; 18°49'04.4''N, 98°53'05.7''E, 356 m; 18.80°N, 98.92°E, 1100 m; 18.82°N, 98.89°E, 1550 m; 18.80°N, 98.90E, 1250 m: Chiang Mai Province, Doi Inthanon National Park (data lost): Mae Hong Son Province, 22 km N of Mae Hong Son, 19.5°N, 97.95°E, 930 m: Nan Province, Doi Phu Kha National Park; Office 6, 19°12.349'N, 101°4.617'E, 1360 m; Office 11, 19°12.458'N, 101°4.866'E, 1359 m; Office 12, 19°12.138'N 101°4.711'E, 1331 m: Phitsanulok Province, Thung Salaeng Luang National Park, 16°50.641'N, 100°52.894'E, 557 m: Lampang Province, Chae Son National Park; Doi Laan unit-2, 18°51.815'N, 99°22.122'E, 1413 m; Doi Laan unit-1, 18°50.826'N, 99°21.71'E, 1413 m; campground/lavatory, 18°49.894'N, 99°28.354'E, 467 m; Mae Paan unit; 18°49.644'N, 99°24.711'E, 815 m: Kamphaeng Phet Province, Mae Wong National Park, Chong Yen, 16°5.212'N, 99°6.576'E, 1306 m: Loei Province, Phu Ruea National Park; Sa Sawan, 17°30.735'N, 101°20.601'E, 1352 m; Pah Lo Noy, 17°30.502'N, 101°20.868'E, 1343m; Nature trail, 17°30.74'N, 101°20.65'E, 1353 m; Huay Taey ditch, 17°30.128'N 101°20.339'E, 1233 m; Pan Hin Khan Maak ditch, 17°30.042'N 101°20.474'E, 1219 m: various dates 2006–2011 (QSBG and NMGW).
Diagnosis. A yellow legged species with tip (and occasionally dorsum) of hind femur blackish. The front tibia is conspicuously darker than the mid tibia and the hind tibia yellowish or suffused blackish at least near base and tip. The antennal stylus is distinctly subplumose with a bare tip. Both left and right surstyli are narrowly elongate but the right surstylus is minutely serrate apically. The hypandrium has two broad apical lobes. Tergite 8 of females encircles the abdomen and sternite 8 has dark posteroapical lateral extensions, appearing broadly T-shaped in posterior view.
Description. Male: length 3.1–4.2 mm. Head subshining black; face dark, blackish yellow below. Postocular setae black, a few paler hairs on lower occiput. Antenna black, postpedicel ovate in lateral view, ~2.5X long as wide; stylus ~5X long as postpedicel, black and distinctly subplumose on basal 0.8–0.85, bare and somewhat whitish in some views distally. Mouthparts blackish, palpus very narrow, with fine apical seta. Thorax with ground colour black, postalar callus, scutellum basally and pleura somewhat paler; scutum (especially at sides and about prescutellar area) and pleura dusted; acr biserial, dc uniserial, small and fine; posterior dc and acr, upper npl (2X long as lower npl), pa and 2 sct distinct, other setae small, hair-like. Legs mostly yellow with F 3 on apical 0.1, F 1 and F 2 very narrowly at tip blackish; T 1, T 3, sometimes F 3 vaguely on dorsum, and posterior tarsi somewhat darker. Coxae with pale hairs and bristles. F 1 with erect pv hairs not longer than limb is deep. F 2 slightly distorted, weakly concave in front about 0.3 from base where ad series of fine bristles almost as long as limb is deep. F 3 (Fig. 3) moderately inflated, widest 0.6–0.7 from base; viewed laterally upper margin convex, lower margin linear; ventral spines black, comprising ~7–8 strong bristles (some of which on proximal 0.7 are slightly longer than limb is deep) behind which are ~10–12 mostly shorter and more evenly sized bristles, occasionally a few extra bristles between the rows especially near base; pv fringe with ~3 strong black bristles on distal 0.3, otherwise weakly developed and yellowish; 3–4 black curved anterior proclinate bristles on distal 0.5. T 1 usually with fine but distinct hair dorsally at 0.6 and 1 somewhat longer seta anteroapically in apical circlet, otherwise short-haired. T 2 with strong bristles dorsally at ~0.2 and ~0.4–0.5 from base and 1 rather longer bristle ventrally at ~0.5; apical circlet with 1 av bristle much longer than others. T 3 somewhat inflated distally, ~1.5–2.0X wide at tip than at base; 1 strong bristle dorsally ~0.5–0.6 from base; apical circlet with 3 distinct bristles. MT 1 and MT 2 with distinct ventrobasal bristle; also MT 2 with distinct ventral bristle near middle. Wing membrane tinged yellowish brown, veins brown; stigma distinct, reaching costa at ≥0.9 distance between end of R 1 and R 2+3. Squamae with pale hairs. Halter white. Abdomen subshining brownish black, tergites with faintly bronze reflections, tergites 2 and 3 with long pale to brownish bristles on posterior margin, distal segments with shorter hairs. Terminalia (Figs 141–147) black, with black setae; left epandrial lamella (Fig 142) with strong bristles; left surstylus (Figs 145–147) long, narrow, wider subapically; right surstylus long, narrow, serrate apically (Fig. 144); hypandrium (Fig. 143) with 2 broad apical lobes. Female. Similar to male but F 3 much less strongly inflated, widest ~0.8–0.9 from base; ventral spines comprising 7–8 distinct bristles arranged in single row; pv fringe weaker; usually only 1 distinct proclinate bristle anteriorly near tip. Abdomen with much shorter hairs. Terminalia (Figs 148–150) black, tergite 8 tubular, encircling abdomen; sternite 8 with usually more strongly sclerotized posteroapical lateral extensions, appearing broadly T-shaped in posterior view (Fig. 149), extending dorsally in lateral view (Fig. 150); sometimes posteroapical lateral processes not easily discernable, being weakly sclerotized or with area between them and median part of sternite 8 equally strongly sclerotized.
Comment. Hybos serratus is very similar to H. aceriformis sp. nov. from which is is best distinguished by the form of the male and female terminalia. It might also be confused with H. anisoserratus sp. nov. which is however a smaller species, usually with more extensively yellow legs.
Although described from Sichuan Province China (Yang & Yang 1992) H. serratus is widespread in eastern China, including Henan, Guizhou, Guangxi, Hainan and also occurs in Vietnam (Yang & Yang 2004; Huo et al. 2010; Yang et al. 2010). The species is here recorded from Thailand for the first time where it is widespread north of ~ 16°N, occurring as far south as the northern Tenasserim Hills and Petchabun Range (Fig. 269) but apparently absent from middle and southern parts of the country. In Thailand, H. serratus occurs at elevations of 467–2,174 m but is most abundant in evergreen and other moist forest types above ~ 1,200 m. Adults have been found in all months except January and March (Fig. 297) but adult numbers are clearly correlated with the wet season between late May and December becoming maximal in December and October.
Thailand specimens apparently differ slightly from examples from China and Vietnam in having the hind femur only at most vaguely darkened dorsally but with a blackish tip. Also both left and right surstyli of Thailand specimens are apparently somewhat narrower than ‘typical’ (cf. Yang & Yang 2004, figs 372–373; Yang et al. 2010, fig. 200) but I have little doubt that they are H. serratus. Indeed, there are small differences in characters of the male terminalia within Thailand and furthermore, these differences are consistently present in populations present on disjunct mountain ranges in the country. For example, the apex of the left surstylus is abruptly narrowed apically in specimens from Doi Chiang Dao (Fig. 145) but of different form in examples from Doi Phahompok (Fig. 146) and from Phu Reua (Fig. 147). It is hypothesised that these differences in morphology of the surstyli reflect recent and ongoing active infra-specific radiation in isolated populations. Hybos serratus is very similar to H. anisoserratus sp. nov. in which species account the differences are further discussed.
description: Published as part of PLANT, ADRIAN R., 2013, The genus Hybos Meigen (Diptera: Empidoidea: Hybotidae) in Thailand, pp. 1-98 in Zootaxa 3690 (1) on pages 57-58, DOI: 10.11646/zootaxa.3690.1.1, http://zenodo.org/record/6329811