Laosa (as genus) Edwards, 1926: 48;
Libnotes (Laosa) Savchenko and Krivolutskaya, 1976: 118; Savchenko, 1983: 110; 1989: 326.
Type species. Laosa gloriosa Edwards, 1926 (monotypic).
Adult. Medium sized crane flies, body length 8–15 mm, wings long and comparatively narrow. Vein Sc very long, tip of Sc 1 reaches far beyond branching point of radial sector (Rs). Rs short and straight. Cells r 3 and r 5 with additional cross vein each. Basal deflection of CuA 1 its own length beyond branching point of M (Fig. 2). Male genitalia (Fig. 3) with simple ninth tergite, posterior margin of which widely rounded; gonocoxite with large ventro-mesal lobe; outer gonostylus narrow and slightly arched before apex; inner gonostylus subglobular with well developed rostral prolongation and additional lobe bearing few long apical setae.
Larva. Body white. Head capsule oval, depressed dorsoventrally and slightly reduced. Caudal end of head capsule (frons) rounded. Internolateralia fused with frontoclypeus. Clypeus consists of two parts: preclypeus and postclypeus. Labrum membranous, with groups of hair-like structures on lateral and ventral sides. Posterior end of labrum conical. Mandible large, heavily sclerotised, with two well developed apical teeth; ventral margin with two smaller teeth, dorsal margin with small single tooth. Maxilla well developed, sclerotised at the base and setose at the apex, cardo large. Hypostomal plate heavily sclerotised except apical part and curved along anterior margin. Hypostoma with nine teeth, the median tooth not prominent, lateral teeth short and obtuse. Hypopharynx and prementum dentate. Abdominal segments with dorsal and ventral creeping welts bearing groups of curved spines and setae and bounded by 4–6 transverse rows of fine setae. Spiracular lobes reduced, stigmal field narrowed on inner side. Spiracular field with only one, ventral pair of irregular sclerites. Spiracle oblong and oblique. Anal field consists of two pairs of white, fleshy and long (projecting beyond middle of segment) anal papillae.
The larvae develop in the thickness of the bast fibers of trunks usually laying on the ground or hanging above the ground and covered with the strong, not exfoliating, partly fresh bast. Larvae were recorded in trunks of various deciduous and coniferous trees (Krivosheina and Krivosheina, 2011).
Pupa. Yellowish brown. Cephalic crest and mesonotal spines absent. Abdominal segments III–VII with dorsal and ventral creeping welts. Surface of abdominal segments smooth, without spines. Prothoracic horns large, elongate, directed upward, bent at nearly right angle in apical part (Krivosheina and Krivosheina, 2011).
Subgenus includes 20 species. Most of them recorded from Oriental (9 species) and Australian (8 species) Regions with only three species known from Eastern Palearctic. No fossil species are known (Evenhuis, 2014). It is recorded here from the Korean Peninsula for the first time.