(Figs. 4–6)
Type material. Holotype 3, Russia: Taimyr Peninsula, Ragozinka river bank, 16.VII. 1990, V. Lantsov [ZIN]. Paratype: Russia: 13, Middle Yamal, Nurma-Yakha River, Malaise trap, 12–17.VII. 1991 [ZIN].
Diagnosis. This species keys to D. brevifacies Stackelberg and D. acutangulus Negrobov (see key above). Legs with partly black femora; postpedicel with obtuse apex; clypeus not reaching lower eye margin; mid femur with 2 and hind femur with 1 anterior preapical setae; M 1 + 2 with strong but gentle curvation; costa with short thickening at R 1; lower calypter with yellow-white cilia.
Description. Male: Body length: 4.3–4.6 mm, wing length: 4.3–4.6 mm, wing width: 1.6 mm, antenna length: 1.3 mm, hypopygium length: 1.9 mm.
Head: Face with dark-brown ground color, weakly silvery-white, nearly reaching lower eye margin, in middle about 1.5 times as wide as postpedicel height. Proboscis dark-brown; palpus dirty yellow, with black setulae, whitish pollinose. Frons shining, metallic green-black. Antenna (Fig. 4) black; scape elongated, 2 times longer than high, with row of dense black dorso-lateral setae. Pedicel slightly longer than high, with a ring of small apical setae; postpedicel bud-like, with obtuse-angular apex, hardly longer than high; stylus bisegmented, short, about as long as scape, pedicel and postpedicel combined, shortly haired, simple, located at 2 / 3 of dorsal surface of postpedicel. Lower postocular setae white. Thorax: metallic green-black; pleura weakly grey pollinose; proepisternum with 1 strong black seta and small white hairs. Legs: mainly dirty yellow; all coxae black; trochanters brown; fore femur black-brown except distal 1 / 3; mid femur brownish at base ventrally; hind femur darkened on basal 1 / 3; hind tibia brown-black on distal 1 / 5; hind tarsus black; fore and mid tarsi black from tip of basitarsus. Coxae with white setulae; fore and mid coxae with black apical setae; hind coxa with 1 strong black seta at middle. Femora without long ventral setae. Mid femur with 2 and hind femur with 1 strong anterior preapical setae; mid femur with small posterior preapical seta. Fore tibia with 2 anterodorsal, 2 posterodorsal and 1–2 posterior setae, with 1 fine long dark apicoventral seta. Mid tibia with 4 antero- and 2 posterodorsal setae, with 1 anteroventral seta. Hind tibia inconspicuously thickened at 1 / 3 and at apex, with 4–5 anterodorsal, 2–3 dorsal setae, with 1 ventral at 3 / 4 and preceding row of elongated ventral setulae in middle half, with small posterior apical tooth. All tarsi simple. Pulvilli and claws small. Hind basitarsus with 2–3 strong dorsal, 1–2 short anterior setae, with several short ventral setulae. Tarsomere length ratio: fore tarsus (from first to fifth): 25 / 10 / 7 / 6 / 7, mid tarsus: 38 / 15 / 14 / 10 / 9, hind tarsus: 32 / 30 / 19 / 12 / 10. Wing: hyaline, widely rounded at apex. Costa with short thickening at R 1, half as long as R 1. R 4 + 5 and M 1 + 2 parallel at apex. M 1 + 2 with strong but gentle curvation just before middle of distal part. Distal part of CuA 1 slightly longer than m-cu. Hind margin of wing evenly convex. Lower calypter yellow, with yellow-white cilia. Halter yellow. Abdomen: metallic green-black, shining, with black setae and hairs. Hypopygium black. Apicoventral epandrial lobe brown, broad, rounded at apex, with 1 strong seta and some fine setulae. Surstyli brown. Cercus rounded-ovate, serrate at apex, with falcate setae, yellow-grey, darker along distal margin.
Female: Unknown.
Distribution. Dolichopus lantsovi is known from the two arctic regions of Siberia, i.e. from easternmost point of the Yamal Peninsula (at latitude 68 º 30 ’) and from westernmost point of the Taimyr Peninsula (at latitude 73 º 30 ’).
Etymology. The species is named after the Russian dipterist Dr. V. Lantsov, who collected the holotype.