Medium-sized flies (5.0–12.0 mm). Male frons narrow, frontal vitta brown to black, with longitudinal crinkle, fronto-orbital plate and parafacial with gleamy yellowish-white and silver pruinosity, all with small hairs, fronto-orbital plate with transverse strip, parafacial and gena broad, frontal angle and vibrissa angle all projecting, gena about ½ of eye in height, antenna scape and pedicel red-brown to black, most of first flagellomere red-brown, first flagellomere at least 2.0 times as long as pedicel, the longest hair shorter than width of first flagellomere, palpus yellow-brown, without facial carina; thorax black and green, with white pruinosity, with outer posthumeral seta, acr (1–2) + (2–4), dc (2–3) + (3–4), ial (0–1) + (3–4) (expect O. dynatophallus sp. nov, O. franzaosternita sp. nov and O. occidentalis Feng, 2003, with 2 post intra-alar setae), distance between acr rows narrow, scutum usually with 3 indistinct vittae, katepisternum 2+1; m1+2 vein with angulated bend, lower calypter with sparse dark ciliae, halter yellow-brown; legs black; abdomen with light pruinosity, only tergite 5 with many discal setae, epandrium and basal parts of surstyli red-brown, paraphallus short, distiphallus long. Female oviscapt short.

Male: Body length 9.0–9.5 mm.

Head. Eye bare; width of frons equals in width or broader than the distance between outer margins of posterior ocelli, frontal vitta black, slightly narrower than fronto-orbital plate, at its narrowest point, 14–15 pairs of frontal setae, without orbital setae; fronto-orbital plate and parafacial with cuprum-grey pruinosity, parafacial about 2.5 times as wide as first flagellomere, more than ½ length of one eye, antennae black, first flagellomere about 2.5 times as long as pedicel, basal ¼ of arista becoming thick, basal ¾ of arista plumose, most of aristal hairs about 1.2–1.3 times as wide as first flagellomere, without facial carina, lower ⅓ of facial ridge with small setae, lower parafacial brown, epistoma distinctly situated behind frontal angle in profile, gena black, with grey pruinosity, gena about ⅗ of eye in height, genal hairs black, and postgena setae light-yellow, prementum without pruinosity, slightly shining, about 2.5 times as long as broad, palpi brown yellow, longer than prementum distinctly.

Thorax. Ground color dark black and slightly dark green, with grey pruinosity, presutural area of scutum with 4 black vittae, postsutural area of scutum with 5 black vittae, and the median vitta reaching scutoscutellar suture; acr 2+3, dc 3+3, ial 0+2, posthumeral setae 1+1, pra about 1.2 times as long as posterior notopleural setae; notopleuron and lateral and ventral margins of scutellum with black hairs, prosternum, propleuron and anepimeron all with hairs, katepimeron bare, meron with row of setae; anterior and posterior spiracles dark brown, katepisternal setae 2+1.

Wing. Base slightly brown; basicosta black, without costal spine, both surfaces of radial node with setae, m-m crossvein S-shaped, calypteres dark brown, lower calypter with small lobule, inside it with few setae in the middle; with anterior paracalyptral tuft, but without posterior paracalyptral tuft; halteres brownish-yellow.

Legs. Entirely black; ventral surface of fore tarsus without tenant hairs, fore tibia with 5–6 ad, 1 ad distinct, 1 pv; mid femur av distinct, becoming short apically, with a complete pv row, strong; mid tibia with 1 v, I ad, 2 p; hind femur with a complete av row, and a row of strong pv in basal ⅗ hind tibia with 1 av, 2 ad, 3 pd, 1 short preapical pv.

Abdomen. Olive green, ovum-shaped, with few grey pruinosity, without distinct shifting patches, tergites 3–5 with distinct black median vittae, posterior marginal setae of tergite 3–6 complete; sternite 1 with hairs, sternite 5 trapezia-shaped, and its lateral lobe with 2–3 long setae.

Female: Unknown.

Holotype: Male, P.R. China: Sichuan Province: Kangding: Mt. Zheduo, 4200 m altitude, 7-VI-2006, collected by Chun-tian Zhang. Paratype: 1 male, same data as holotype.

Etymology: The species name is from the Greek words dynat meaning muscular and phall meaning aedeagus, referring to the thick and strong aedeagus of the species. (Figs. 12–13)

Remarks: This new species resembles Onesia jiuzhaigouensis Chen et Fan in Chen et al. (1992), but it differs from the latter in male body length 9.0–9.5 mm, frons equals in width or broader than the distance between outer margins of posterior ocelli, fronto-orbital plate and parafacial with cuprum-grey pruinosity, parafacial about 2.5 times as wide as first flagellomere, excess ½ the length of one eye, lower ⅓ of facial ridge with small setae, genal height about ⅗ of eye height, ial 0+2, posthumeral setae 1+1, mid tibia without pd, hind tibia with 1 av; surstylus triangle-shaped in profile, middle section of paraphallus broad and large, distal part of it with hamulus.

Distribution—Kangding, Sichuan, China.

Male: Body length 5.5–8.2 mm.

Head. eye bare; width of frons equal to or larger than the distance between outer margins of posterior ocelli, frontal vitta black, its narrowest point about ⅓ as wide as one fronto-orbital plate, 11–12 pairs of frontal setae, without orbital setae; ocellar seta subequal to inner vertical seta and frontal setae, fronto-orbital plate and parafacial with lightgrey pruinosity, parafacial about 1.8–2.0 times as wide as first flagellomere, about ⅓ eye in length, on basal half of parafacial with 4–5 rows short hairs, antennae black-brown mostly, apical part of pedicel and basal part of first flagellomere red- brown, first flagellomere about 2.2 times as long as pedicel, the basal ¼ of arista becoming thick, the basal ¾ of arista plumose, the longest hairs subequal to first flagellomere in width, facial carina lower and narrow, lower ⅓ of facial ridge with small setae, lower of parafacial brown, epistoma distinctly situated behind frontal angle in profile, gena black, with grey pruinosity, genal height about ⅓ of eye height, genal hairs black, and postgena with sparse light-yellow hairs, occiput lateral area with hairs, prementum without pruinosity, shining, about 2.5 times as long as broad, palpi brown yellow, and equal to or longer than prementum.

Thorax. Ground color black, with light grey pruinosity, scutum with 4 black vittae, acr 1+3, dc 3+3, ial 0+2, posthumeral setae 1+1, pra about 1.3 times as long as posterior notopleural seta; notopleuron and lateral and ventral margins of scutellum with black hairs, ventral surface of distal part bare, prosternum, propleuron and anepimeron all with hairs, katepimeron bare, meron with row of setae; anterior and posterior spiracles dark brown, katepisternal setae 1+1.

Wing. Wing base light brown, vein brownish, basicosta dark brown, costal spine short and small, both surfaces of radial node with setulae, m-m cross vein lightly S-shaped, calypteres light brown, lower calypter with small lobule, inside it with 3–4 setulae in the middle; with anterior paracalyptral tuft, but without posterior paracalyptral tuft; halteres light brown.

Legs. Entirely black; ventral surface of fore with few tenant hairs, fore tibia with 2–3 medial ad, slightly longer than body hairs, 1–2 medial pv; mid femur av rows short and thin, hairs-like, with a complete pv row, mid tibia with 1 submedial ad, strong, 2 medial v, 1 submedial p; hind femur with a complete but sparse av row, and a row of strong pv in basal half, ventral surface of basal part with setae, fringe-like, hind tibia with 1 av, 2–3 ad, 2–3 pd; tarsi slightly shorter than tibiae, claw and pulvilli developed, subequal to the length of 5^th tarsomere.

Abdomen. Black, ovum-shaped, with dense light grey pruinosity, each tergite with narrow median stripe, 2 sides with shifting patches, sternite 1 with hairs, distal part and lateral of abdomen with slightly long setae.

Female: Body length 7.8–8.2 mm. Frons about 0.36 times as wide as head, frontal vitta about 1.7 times as wide as 1 fronto-orbital plate, frontal triangle reach to ⅓ of upper half of frons, without distinct interfrontal seta, but with 2–3 pairs of small setae, 7–8 pairs of intilted frontal setae, reach to 2 sides of anterior ocellus, 2 pairs of proclinate orbital setae, 1 pair of upper orbital setae, inner vertical seta about 2 times as long as ocellae seta, ocellae seta subequal to frontal setae in length, lower half of fronto-orbital plate and upper half of parafacial with many small hairs, parafacial about 2.5 times as wide as first flagellomere, genal height about ½ of eye height; ventral surface of front legs without tenant hairs, basal part of hind femur with 2–3 fringes, claw and pulvilli slightly short, about ⅔ of fifth tarsomere in length; others characteristic the same as male's.

Holotype: Male, P.R. China: Ningxia Autonomous Region: Jingyuan: Lvyuan Forestry centre, 1700–1800 m altitude, 30-VI-2008, collected by Jiayu Liu. Paratype: 2 females, same data as holotype; 1 male, Jingyuan: Hongxia Forestry centre, 2100 m altitude, 14-VII-2008, collected by Zhi-yuan Yao; 1 male, Jingyuan: Heshangpu Forestry centre, 2100–2300 m altitude, 26-VI-2008, collected by Jiayu Liu; 1 female, Jingyuan: Qiuqianjia Forestry centre, 1800 m altitude, 3-VII-2008, collected by Jia-yu Liu; 2 males, Longde: Sutai Forestry centre, 2140–2200 m altitude, 25-VI-2008, Jia-yu Liu, 1 male, collected by Zhi-yuan Yao.

Etymology: The species name is from the Greek words franza meaning fringe and sternita meaning sternite, referring to inner margin of lateral lobe of sternite 5 with thin fringe.

Remarks: The male genitalia of this new species resembles Onesia huaxiae Feng et Xue 2000, but it differs from the latter in inner margin of lateral lobe of sternite 5 with thin fringe, in profile, surstyli bend distinctly, distal part of cerci slightly flat, in dorsal view, surstyli becoming thin.

Distribution—Jingyuan and Longde, Ningxia Autonomous Region, China.