3.3.1. Key to nigrum group

1 Anterior angles of pronotum strongly protruded anteriad. Elytra markedly wider than long. Aedeagus as in Fig. 77. Habitus as in Fig. 67. Body length: 3.90–4.20 mm. China: Yunnan ........................................ A. conjunctum sp.n.

- Anterior angles of pronotum slightly protruded anteriad. Elytra as wide as long or slightly longer than wide............. 2

2 Punctation of pronotum very dense. Aedeagus very wide basally, markedly, evenly narrowed toward apex of median lobe (Fig. 80). Habitus as in Fig. 68. Body length: 3.50–4.27 mm. China: Yunnan ........................ A. densepunctatum sp.n.

- Punctation of pronotum sparse. Aedeagus of different shape, not very wide basally (Figs. 70, 72), sometimes quite narrow (Fig. 82)................................................................................................ 3

3 Pronotum slightly flattened in cross section, with indistinct medio-basal impression. Aedeagus as in Fig. 72. Habitus as in Fig. 66. Body length: 4.15–4.37 mm. China: Gansu ............................................. A. anishchenkoi sp.n.

- Pronotum very convex, with deep medio-basal impression.................................................... 4

4 Elytra as wide as long. Apical part of median lobe of aedeagus narrow, apical portions of parameres very wide (Fig. 82). Habitus as in Fig. 69. Body length: 4.00– 4.71 mm. Nepal, Bhutan ........................................ A. ivani sp.n.

- Elytra slightly longer than wide. Apical part of median lobe of aedeagus wide, apical portions of parameres relatively narrow (Fig. 70). Habitus as in Fig. 65. Body length: 3.44–4.75 mm. India........................ A. nigrum (Cameron, 1924)