Key to the known species of Aancistroger (except A. inarmatus)

1 The shape of female seventh abdominal tergite similar to other abdominal tergites, nearly rectangular, longer than broad, basal area with short transverse copulatory depressions, apical area without membranous area; ovipositor straight, apex obtusely rounded; hooks of male ninth abdominal tergite thin, curved inwards, tenth abdominal tergite with 1 pair of heavily sclerotized hooks, its basal area slightly swollen and apices directing backward and slightly outward................... A. primitivus

- The shape of female seventh abdominal tergite obviously different from other sternites, wider than long, between the apical area and basal area of subgenital plate with membranous area...................................................... 2

2 Basal area of female seventh abdominal sternite with 1 folded process, apical area with narrow membranous area, which indistinctly separated from subgenital plate; posterior margin of female subgenital plate obtusely rounded, slightly concave in the middle; male ninth abdominal tergite long, curved ventrad, posterior margin of subgenital plate medially projected.................................................................................................. A. elbenioides

- Basal area of female seventh abdominal sternite with central depression, distinctly separated from subgenital plate by wide membranous......................................................................................... 3

3 Posterior margin of female subgenital plate with deeply acute-angled concavity, lateral margins of basal area convex.................................................................................................... A. similis

- Posterior margin of female subgenital plate with shallowly obtuse-angled concavity, lateral margins of basal area slightly convex................................................................................................ 4

4 Basal area of female seventh abdominal sternite with membranous area, posterior margin of subgenital plate truncate; male ninth abdominal tergite with 1 pair of short spines on lateral margin, posterior margin of subgenital plate angular concave............................................................................................... A. sinicus

- Basal area of female seventh abdominal sternite without membranous area; posterior margin of seventh abdominal sternite concave....................................................................................... A. vietus