Amphichroum, Kraatz, 1857

Shavrin, Alexey V. & Smetana, Aleš, 2018, New species of the genus Amphichroum Kraatz, 1857 (Coleoptera: Staphylinidae: Omaliinae: Anthophagini) from China, Zootaxa 4508 (3), pp. 377-402 : 401-402

Key to species of Amphichroum of China

1 Basal portion of internal sac with paired, very large sclerotized structures......................................... 2

- Basal portion of internal sac with significantly smaller sclerotized structures or without them......................... 4

2 Pronotum with distinct longitudinal reddish-brown spot. Median lobe ( Fig. 14) markedly, evenly narrowed toward acute apex; internal sac with two very long apical thorns ( Fig. 15). Body length:2.00–2.35. Habitus as in Fig. 4. Yunnan................................................................................................... A. maculosum sp.n.

- Pronotum without spot. Shape of median lobe and internal sac different........................................... 3

3 Elytra longer than wide. Forebody yellow to yellow-brown, abdomen reddish-brown. Parameres slightly exceeding apex of median lobe; sclerotized structures in basal part of internal sac very large and wide ( Fig. 12). Body length:2.10–3.65. Habitus as in Fig. 3. Sichuan.................................................................. A. longilobatum sp.n.

- Elytra distinctly wider than long. Body yellow-brown to reddish-brown. Parameres distinctly exceeding apex of median lobe; sclerotized structures in basal part of internal sac smaller and narrower ( Fig. 20). Body length:3.00–3.15. Habitus as in Fig. 16. Sichuan............................................................................. A. propinquum sp.n.

4 Apical portion of internal sac with wide thorns.............................................................. 5

- Apical portion of internal sac without wide thorns............................................................ 6

5 Aedeagus moderately wide, with short parameres ( Fig. 5); internal sac with two pairs of wide thorns in apical and complicated sclerotized structures in basal portion ( Fig. 5). Body length:2.85–3.10. Habitus as in Fig. 1. Yunnan.. A. angustilobatum sp.n.

- Aedeagus narrow, with longer narrow parameres ( Fig. 24); internal sac with several wide thorns in apical and sclerotized ringlike structure in basal portion ( Fig. 25). Body length:2.20–3.75. Habitus as in Fig. 18. Yunnan............ A. schuelkei sp.n.

6 Median lobe with rounded apex.......................................................................... 7

- Median lobe with subacute or narrowly arcuate apex.......................................................... 8

7 Parameres considerably exceeding apex of median lobe, basal portion of internal sac without oval structure ( Fig. 22–23). Head, pronotum and abdomen reddish-brown, elytra yellow-brown to brown. Body length: 2.81–3.75 mm. Habitus as in Fig. 17. Sichuan........................................................................... A. rotundatum sp.n.

- Parameres moderately exceeding apex of median lobe, basal portion of internal sac with oval structure ( Fig. 39–40). Forebody yellow-brown, abdomen reddish-brown. Body length:3.20–3.85. Habitus as in Fig. 34. Tibet............ A. tibetanum sp.n.

8 Anterior angles of pronotum distinctly protruded anteriad. Median lobe with subacute apex; internal sac with ring-like structure in basal part ( Figs. 8–9). Body length:3.55–4.95. Habitus as in Fig. 2. Yunnan...................... A. assingi sp.n.

- Anterior angles of pronotum not protruded anteriad. Median lobe with narrowly arcuate apex; internal sac without ring-like structure in basal part.................................................................................. 9

9 Median lobe narrow; parameres short, reaching apex of median lobe (see Watanabe 1999: Fig. 2). Body length: 2.80–3.20 mm. Habitus (see Watanabe 1999: Fig. 1). Guangxi.................................... A. miaoershanum Watanabe, 1999

- Median lobe wider; parameres longer, distinctly exceeding apex of median lobe................................... 10

10 Apical portion of median lobe wide; parameres relatively wide ( Fig. 37). Body length:3.50–4.80. Habitus as in Fig. 33. Sichuan............................................................................... A. subelongatum sp.n.

- Apical portion of median lobe narrow; parameres narrow..................................................... 11

11 Elytra slightly wider than long. Aedeagus narrow; basal portion of internal sac with wide field of large thorns ( Fig. 35). Body length: 2.90–4.00 mm. Habitus as in Fig. 32. Shaanxi.......................................... A. subaequale sp.n.

- Elytra slightly longer than wide. Aedeagus wider basally; basal portion of internal sac with very wide, strongly sclerotized thorns ( Fig. 27).Body length:2.90–3.95. Habitus as in Fig. 19. Sichuan............................ A. squamosum sp.n.