Key to subgenus and Chinese species of the genus Stenobracon Szépligeti

1. Second metasomal tergite without medio-basal area, or area indistinct; fore wing vein 3-SR 1.8–2.7 × longer than vein r, rarely up to 1.5 ×; antero-lateral grooves of third tergite distinctly crenulate and rather wide; sixth tergite yellowish brown (not found in China)................................................................. subgenus Euvipio Szépligeti, 1904

- Second metasomal tergite with (minute) medio-basal area, often weakly indicated and transverse; fore wing vein 3-SR 1.2–1.8 × longer than vein r, rarely up to 2.2 ×; antero-lateral grooves of third tergite comparatively narrow or obsolescent, often weakly crenulate or smooth; sixth tergite frequently black (subgenus Stenobracon Szépligeti, 1901)......................... 2

2. Metasomal tergites of female entirely yellowish brown; third and fourth tergites largely rugose; hind wing vein 1r-m 1.0–1.6 × longer than vein SC+R1; head of male dorsally brownish yellow or with a transverse narrow band across stemmaticum between compound eyes.............................................................. S. (S.) deesae (Cameron, 1902)

- At least fifth and sixth metasomal tergites of female black; third and fourth metasomal tergites smooth or partly rugose; vein 1r-m of hind wing variable, shorter to longer than vein SC+R1; head of male dorsally completely black or yellowish brown. 3

3. Second metasomal tergite of female 0.8–1.1 × wider than long (of male 0.9–1.2 ×); third metasomal tergite smooth, without or with only a trace of groove defining posterior margin of antero-lateral area............... S. (S.) oculatus Szépligeti, 1901

- Second metasomal tergite of female 1.1–1.5 × wider than long (of male 1.2–1.8 ×); third metasomal tergite usually rugose medio-basally or posteriorly, with well-developed groove defining posterior margin of antero-lateral area............... 4

4. Second submarginal cell of fore wing rather long and vein 3-SR of female 2.2 × longer than vein r (of male 2.7 ×); vein 1r-m of hind wing of female 0.8 × longer than vein SC+R1; second metasomal tergite rugose posteriorly and sublaterally; vertex of female with a black spot on either side of lateral ocellus reaching eye orbits..................... S. (S.) longatus sp. nov.

- Second submarginal cell of fore wing short, vein 3-SR of female 1.5–1.9 × longer than vein r (of male 1.7–2.0 ×); vein 1r-m of hind wing 1.0–1.4 × longer than vein SC+R1; second metasomal tergite smooth posteriorly and sublaterally; vertex of female completely black or with a black transverse band across stemmaticum between compound eyes................................................................................................ S. (S.) nicevillei (Bingham, 1901)