Key to species of the Stenus viridanus group from China

(Examining aedeagus is the most reliable way to identify species of S. viridanus complex.)

1 Pronotum with short but distinct setae, elytra without vorticose sculpture, eyltra wider with HW/EW=0.88–0.92, male sternite

IX and valvifers with apicolateral portion serrate, sclerotized spermatheca undetectable......... S. cyanogaster complex...2 - Pronotum with extremely short and usually unnoticeable setae, elytra each with vorticose sculpture in posterial half, eyltra narrower with HW/EW=0.88–1.00, sternite IX and valvifers with long apicolateral projections, spermatheca sclerotized........................................................................................ S. viridanus complex...3 2 Body with faint blue metallic tint, head with midline smooth, elytra relatively wider (HW/EW=0.98–1.05), elytral punctation more confluent, aedeagus as in Fig. 15 A (in Rougemont, 1983)....................................... S.cyanogaster

- Body with strong blue metallic tint, head with midline reticulated, elytra relatively narrower (HW/EW=1.05–1.10), elytral punctation less confluent, aedeagus as in Figs. 16, 17 ............................................. S. panyuhongae

3 Head distinctly narrower than elytra (HW/EW=0.88–0.95).....................................................4

- Head almost as wide as elytra............................................................................5

4 Elytra relatively larger (EL: 1.46–1.54 mm, EW: 1.40–1.44 mm), aedeagus as in Fig. 94 in Puthz, 2008, spermatheca as in Fig. 95 (in Puthz, 2008)........................................................................... S.viridivestis

- Elytra relatively smaller (EL: 1.29–1.47 mm, EW: 1.22–1.37 mm), aedeagus as in Fig. 2 A (in Zheng, 1992), spermatheca as in Fig. 2 D (in Zheng, 1992)........................................................................ S.viridanus

5 Punctation of pronotum and elytra more confluent, aedeagus as in Figs. 9, 10, female unknown.................. S. liuyei

- Punctation of pronotum and elytra less confluent.............................................................6

6 Aedeagus (Fig. 97 in Puthz, 2008) with parameres distinctly longer than median lobe, median lobe with apical sclerotized area shorter, spermatheca as in Fig. 95 (in Puthz, 2008).................................................. S.viridicans

- Aedeagus (Fig. 6 in Puthz, 1975) with parameres as long as median lobe, median lobe with apical sclerotized area longer, spermatheca as in Figs. 100, 101 (in Puthz, 2008).................................................... S. viridimicans