Key to species of the genus Straneostichus Sciaky, 1994

1. Vertex with fine and dense punctures; pronotal basal fovea composed of two fused grooves (outer groove present); pronotum usually with only one mid-lateral seta (occasionally two, the basolateral seta not included); outer surface of metatarsomere I distinctly ridged on three-fourth or more of its length; in lateral view, apical lamella of aedeagus evenly curved to venter ( fischeri -group)...................................................................................... 2

- Vertex impunctate; pronotal basal fovea composed of single long groove (outer groove absent); pronotum usually with two or more mid-lateral setae (occasionally one); outer surface of metatarsomere I faintly ridged less than half of its length; in lateral view, apical lamella of aedeagus more or less sinuate (vignai- group)............................................ 8

2. Pronotal basal fovea sporadically punctate, mid-basal area between basal foveae completely impunctate (Figs 21A–B); elytral shoulders strongly narrowed; apical lamella of aedeagus much longer than maximum width, L/W = 1.55-1.75 (Figs 3–4, 6–7) ................................................................................................... 3

- Pronotal basal fovea densely punctate, mid-basal area between basal foveae more or less punctate (Figs 21C–G); elytral shoulders moderately narrowed; apical lamella of aedeagus longer or nearly as long as maximum width, L/W = 1.00-1.60 (usually less than 1.40) (Figs 9, 11–12, 14–15, 17, 19–20)..................................................... 4

3. Elytral striae near base with fine punctures (Fig. 21A); elytra strongly elongated, EL/EW = 1.50-1.56; basal portion of aedeagus slightly thickened, in dorsal view apical lamella strongly bent rightward (Figs 3A, 3A); N. Sichuan, S. Gansu ... S. ovipennis

- Elytral striae completely impunctate (Fig. 21B); elytra less elongated, EL/EW = 1.43-1.46; basal portion of aedeagus strongly thickened, in dorsal view apical lamella only slightly bent rightward (Figs 6A, 7A); C. Sichuan .......... S. politus sp. nov.

4. Pronotal anterior margin subequal to posterior margin (PPW/APW = 0.98–1.05, mean 1.02); endophallic piece hardly visible (depigmented) on ventral surface of apical orifice (Figs 9, 11–12)............................................... 5

- Pronotal anterior margin slightly wider than posterior margin (PPW/APW = 0.85–0.95, mean 0.92); endophallic piece visible (well pigmented) on ventral surface of apical orifice (Figs 14–15, 17, 19–20)...................................... 6

5. Pronotum finely punctate on mid-anterior area; posterior angles forming a clear denticle (Figs 21C); median lobe of aedeagus very narrow on middle portion, apical lamella a little widened in dorsal view (Fig. 9A); Shaanxi .............. S. haeckeli

- Pronotum impunctate on mid-anterior area; posterior angles evident but usually not forming denticle (Fig. 21D); median lobe of aedeagus thicker on middle portion, apical lamella strongly widened in dorsal view (Figs 11A, 12A); Gansu, Qinghai ............................................................................................... S. fischeri

6. Pronotal posterior angles rarely forming denticle (Fig. 21E); elytral striae almost impunctate; middle portion of median lobe of aedeagus very thick (MW/ML = 0.23–0.27); endophallic piece on apical orifice strongly sclerotized and thickened, visible in lateral view (Figs 14C, 15C); Shaanxi, Henan ......................................................... S. puetzi

- Pronotal posterior angles usually forming clear denticle (Fig. 21F‒G); elytral striae with fine but distinct punctures; middle portion of median lobe of aedeagus thinner (MW / ML = 0.15–0.22); endophallic piece on apical orifice moderately sclerotized, not thickened, invisible in lateral view; Gansu, Qinghai, Ningxia ............................................... 7

7. Maximum width of pronotum just before middle (APL/PL = 0.42‒0.44); elytral striae shallower; middle portion of median lobe of aedeagus thinner (MW/ML = 0.15‒0.17) (Fig. 17C); in dorsal view, apical lamella strongly bent rightward, apex nearly truncate (Fig. 17A‒B); Ningxia ................................................... ..…… S. liupanensis sp. nov.

- Maximum width of pronotum near anterior third (APL/PL = 0.34–0.38); elytral striae deeper; middle portion of median lobe of aedeagus thicker (MW/ML = 0.19–0.22) (Figs 19C, 20C); in dorsal view, apical lamella not bent rightward, apex rounded (Figs 19–20); Gansu, Qinghai ............................................................. S. ganqingensis sp. nov.

8. Pronotum nearly trapezoidal (Figs 22‒23, 25‒26), posterior angles more or less evident, forming rectangular or obtuse angles; elytral basal pores present; frontal grooves moderately deep................................................... 9

- Pronotum nearly rounded (Figs 24, 27), posterior angles obtuse-rounded; elytral basal pores absent; frontal grooves very faint .................................................................................................. 10

9. Dorsal surface metallic purple or coppery (Figs 22‒23); pronotal lateral margins strongly sinuate before posterior angles, which are nearly rectangular or a little pointed; median lobe of aedeagus slenderer with longer apical lamella, in dorsal view, apical lamella a little longer than maximum width; Central and North Sichuan, Gansu, Shaanxi, Ningxia .............. S. vignai

- Dorsal surface metallic green or dark blue (Figs 25‒26); pronotal lateral margins faintly sinuate or nearly straight before posterior angles, which are obtuse or slightly pointed; median lobe of aedeagus stouter with shorter apical lamella, in dorsal view, apical lamella evidently longer than maximum width; North Yunnan, South Sichuan ............. S. kirschenhoferi

10. Elytral odd intervals much wider and with shallower microsculpture than even ones (Fig. 27A‒C); lateral margins evenly curved in their full length; in lateral view, apical lamella of aedeagus longer and more strongly curved ventrally.................................................................................................... S. rotundatus

- Elytral odd intervals a little wider than and with similar microsculpture as even ones (Fig. 24); lateral margins nearly straight before posterior angles; in lateral view, apical lamella of aedeagus shorter and slightly curved ventrally.......... S. farkaci