Key to genus and tribe of Iassinae (males) from China

1. Anterior margin of head well delimited, transition from crown to face distinctly angulate, ocelli on margin [ Krisnini]...... 4

- Anterior margin of head usually not well delimited, but if so, then ocelli on face below crown margin.................. 2

2. Pronotum strongly convex and declivous anteriorly; male subgenital plate short and concealed by pregenital sternite [Hyalojassini].............................................................................................. 5

- Pronotum slightly convex; male subgenital plate slender and extended beyond pregenital sternite [Iassini]............... 3

3. Style apophysis short and broad; apex of subgenital plate curved to middle............................ Iassus Fabricius

- Style apophysis slender, elongate; apex of subgenital plate straight............................. Batracomorphus Lewis

4. Forewings with extra crossveins in distal half (Figs. 3, 6); eighth sternite wide, with many longfine setae (Figs. 59–62); subgenital plates without setae laterally........................................................... Krisna Kirkaldy

- Forewings without extra crossveins in distal half; eighth sternite wide, without setae; subgenitalplate with many short spinelike setae laterally......................................................................... Gessius Distant

5 Subgenital plates with mesal margins convergent distally, apices strongly bent or with toothlike ventral projection................................................................................. Trocniassus Dai, Dietrich & Zhang

- Subgenital plates with mesal margins strongly divergent distally, apices unmodified................................ 6

6. Connective well delimited, joint with aedeagus flexible (Figs. 36)................... Decliviassus Dai, Dietrich & Zhang

- Connective membranous or immovably fused to aedeagus..................................................... 7

7. Sclerotized connective absent; apodeme of male style longer than apophysis (Fig. 14)...... Siniassus Dai, Dietrich & Zhang

- Sclerotized connective present; apodeme of male style shorter than pophysis....................................... 8

8. Forewing appendix well developed, more than half width of inner apical cell; subgenital plates close together at base or absent...................................................................................... Trocnadella Pruthi

- Forewing appendix weakly developed, less than half width of inner apical cell; subgenital plates well separated from each other at base.......................................................................................... 9

9. Ventral pygofer process well developed; aedeagus with bidentate distal processes..................... Coriojassus Evans

- Ventral pygofer process absent; aedeagus with distal processes, if present, without teeth................ Hyalojassus Evans