♂ Body-length 6-9 mm; wing-length 5.4-7.7 mm. Body excluding appendages black in ground colour, sometimes more or less brownish especially in smaller specimens. Interfrontalia with whitish grey pollen, which is often more or less tinged with yellow; parafacials in pollinosity silvery grey and sometimes slightly tinged with yellow; cheeks silvery grey or whitish grey in pollinosity, which is usually more or less tinged with yellow or brownish yellow; antennae black; palpi blackish; haustellum with mentum blackish and polished, at most faintly pollinose in part. Thorax rather densely covered with bluish grey pollen, which is usually more or less tinged with yellow or brown; mesonotum variously darkened according to the point of view, when viewed from behind with moderate median vitta and broad lateral patches. Abdomen shining in some lights and largely darkened when viewed from front although densely covered with bluish grey pollen, which is sometimes more or less tinged with yellow or brown; prebasal sclerite very faintly pollinose and shining; basal sclerite rather distinctly pollinose except on polished cephalic margin; median vitta and fore marginal bands narrow or moderate and usually sharp, the former being often interrupted at hind margin of each tergite. Femora blackish, at most slightly yellowish at apex especially on f1 ; in the specimens collected from Hokkaido tibiae yellowish although slightly or strongly darkened on tl and at base of t2 and t3; in the specimens collected from Honshu tibiae strongly darkened and blackish or dark brownish, only occasionally yellow as in the specimens from Hokkaid6; tarsi blackish. Wings dinstinctly tinged with brownish yellow, at base strongly yellow; calyptrae strongly yellow; halteres brownish at base and yellow at knob. Head about 1.3 times as high as long; frons more or less wider than anterior ocellus, usually 1.3-1.5 times as wide as the latter; interfrontalia usually half to two-thirds of anterior ocellus in width, with a pair of strong if; parafrontals with 5-8 ori, and rarely with 1 ors; A3 about 2-2.4 times as long as wide; arista distinctly pubescent, the longest hairs longer than basal diameter of arista, usually about twice as long as the latter; profrons usually about 1.4-1.5 times as wide as A3, but in smaller specimens about as wide as the latter; cheeks about 1.5-1.9 (in smaller specimens about 1.3) times as high as A3-width, with genal setae in 1 or sometimes 2 rows; epistoma more or less behind frons at lunule; palpi slightly longer (in larger specimens) or somewhat shorter (in smaller specimens) than A2 and A3 combined; haustellum slender (although not so in smaller specimens), with mentum more or less longer than palpi. Mesonotum with about 6--10 pairs of short pre aer, of which 1-2 pairs are composed of setae rather longer than the others and sometimes strong; distance between the rows of pre aer being half to two-thirds of that between de and aer, a few or some accessory setulae present between the rows; pra much longer than anterior ntpl, about as long as 1st post de; notopleura with no accessory setulae; mesopleura with 1 or a few anterior mpl rather distinct or not, and with about 10-15 (in larger specimens) or only some (in smaller specimens) accessory setulae around pstg (1 strong and 1-2 weaker); stpt 1: 3, the lowest posterior being well developed or rather weak; scutellum bare on dorsal centre. Abdomen half-depressed, about 2.3--2.7 times as long as wide, and slowly narrowing caudad; 5th tergite with a complete row of strong discal setae. Fore tibia with 1 or sometimes 2 ad and 1 or rarely 2 pv; f2 with no distinct av and on basal half with 3--5 strong pv, the longest one about 1.4-2 times as long as height of the femur; t2 with 1 ad, 2 pd and 2-3 (usually 2) pv; fa with a row of long and strong av, the longest one about 1.8-2.4 times as long as height of the femur, and with a row of pv more or less weaker than the av; ta with 2--4 (usually 3) av, 4-5 (usually 4) ad, 3 pd (sometimes in addition with 1 short pd) and 1 or some pv, apical pd being weak. Wings with costal thorns rather distinct, or minute and only a little stronger than costal setulae; costa haired on ventral surface rather anteriorly; m-m oblique and usually sinuate. ♀ Body-length 6-9.7 mm; wing-length 6-8.6 mm. Interfrontalia orange yellow or reddish brown in ground colour, sometimes darkened near ocellar triangle, and with whitish pollen, which is usually tinged with yellow; parafrontals on upper half darkened in ground colour, and yellowish in pollinosity; parafrontals on lower half, parafacials and cheeks in ground colour orange yellow or reddish brown, at most partly darkened, and in pollinosity slightly or rather distinctly tinged with yellow; occiput blackish in ground colour, and bluish grey in pollinosity, which is more or less tinged with yellow and brown. Thorax densely covered with pale yellowish grey pollen; mesonotum when viewed from front with paramedian vittae between de and aer, and when viewed from behind with narrow or moderate median and broad lateral vittae. Abdomen very thinly covered with bluish grey pollen and shining. In the specimens from Hokkaido legs largely yellow; f1 slightly or largely blackish; f2 and fa at most blackish apically; tibiae darkened at most basally; tarsi blackish. In the specimens from Honshu legs blackish although sometimes yellow as in the specimens from Hokkaido. Wings more yellowish than in male. Head only a little (about 1.1 times) higher than the length; frons about 0.35- 0.42 times as wide as head; interfrontalia about 2.5 times as wide as parafrontalia; parafrontals with 2-3 (rarely 1) strong ors; cheeks with genal setae very short and fine except for 1-2 strong or distinct ones near peristomal setae. Stpl 1 :2. Abdomen with accessory setulae decumbent; discal setae usually indistinguishable from accessory setulae; marginal setae strong. Fore tibia with 1-3 (usually 2) ad and 1-2 (rarely none) pv, and with or without 1 (rarely 2) pd; f2 with a few pv on basal third; t2 with 1 av, 2 ad, 2 pd and 2-4 (usually 2) pv; f3 on basal half with 3-5 pv and near apex with a few pv; t3 with pv sometimes hardly distinguishable from accessory setulae. Wings with costal thorns strong, or minute especially in smaller specimens.