Normally dark, but also a lighter form. In darker form the thorax is grey, with dark grey scutal stripes, scutellum brown and postnotum dark brown; abdomen largely black or dark brown with narrow caudal pale bands, the dark areas on tergites II-IV have a median caudal projection. In the pale forms the scutal stripes are brown and the ground color yellow; with the abdomen the tergites are largely yellow, with a diamond shaped central dark area on segments II-IV.
Wing length about 7.0 mm, posterior margin markedly concave at the end point of Cu(2)(also in female). Cross vein colored.
AR about 5.4. Frontal tubercles oval in shape, 45 x 29 µm. Palp proportions (segments 2-4)(micron) 120 : 310: 260 : 410.Legs generally yellow, with dark knee joints, more conspicuous on fore legs; tarsi I-IV dark on distal 4/5, tarsus V completely dark. LR 1.2-1.3, beard conspicuous, BR 6.5.
Leg lengths (micron) and proportions:
Posterior edge of tergite IX is flat, anal point is slender, apically expanded. Superior volsella closest to E(g) type of Strenzke (1959). Gonstylus narrows relatively sharply over posterior quarter.
Pupa: Notes only that the caudolateral spur is unusual in that it has numerous short spines (see Fig. above) rather than the longer apical spines of most species.
Fourth instar larva: A medium to large plumosus type (length 20 - 28 mm), ventral tubules from 0.5-3.0 mm; anal tubules about 685-735 µm and 2.5-2.76 times longer than wide. Gula darkened Gula darkened on posterior 2/3 with scalloped anterior margin.
Mentum of available specimens very worn but appears the fourth laterals may be partly reduced (type II) and c2 teeth of central trifid tooth are relatively separated from a broad c1 tooth (type IIA).
Ventromental plates about 4.2-4.4 times longer than width to base of striae, separated by about 0.37-0.42 of the mentum width; about 77-107 striae; VMR about 0.33.
Pecten epipharyngis with about 11-15 broad teeth (type B).
Distance between the antennal bases greater than that between the S4 setae which are separated by about 76% of the frontoclypeal width at that point.Antennal segment A1 about half of VHL and about 2.9-3.8 longer than wide (lower value may be due to squashing of the segment during slide mounting), RO about a third to almost halfway up from base of segment; AR about 2.71-2.81, segment proportions (micron) 211 : 41 : 13 : 15 : 8.
Premandible not visible in available specimens.
Mandible with third inner tooth well separated and darkened (type IIIC), about 27-30 furrows on outer surface at the base; 12-16 setae in Pecten mandibularis.
Cytology: Four polytene chromosomes with the thummi-cytocomplex combination: AB, CD, EF, G.
Only nucleolus subterminal on arm G.
Polymorphism in arms A, B and E. A B-chromosome is sometimes present.
The banding sequences of arms E and F were revised by Golygina and Kiknadze (2018).
suwA1: 1 - 2c, 10 - 12a, 13ba, 4a-c, 2g-d, 9 - 4d, 2h - 3, 12cb, 13c - 19
suwA2: from suwA1 by complex inversion.
suwB1: as B1 of borokensis
suwB2: as B2 of plumosus and borokensis
suwC1: 1-2c, 6c-7, 16-17a 6hg, 11d-12, 4-6b, 11c-8, 15-13, 3-2d, 17b-22
suwD1: 1-3, 10b-e, 4-7, 18a-d, 8-10a, 13a-11, 13b-17, 18e-24 as D2 of plumosus and borokensis
suwE1: 1 - 3a, 4c - 10b, 3e-b, 4b - 3f, 10c - 13 as E1 of plumosus and borokensis
suwE2: 1 - 3a, 4c - 10b, 3e-b, 4ba, 10e-c, 3f, 10f - 13
suwE3: 1 - 3a, 4c - 6d, 7c - 6e, 7d - 10b, 3e-b, 4b - 3f, 10c - 13 (from E1)
suwF1: 1a - 10d, 18c-a ,11a - 17d, 18d - 23 as F2 of borokensis
suwG1: as G2 of borokensis
Found: Type locality - Lake Suwa, Honshu, JAPAN.
Japan - Tsukuba.