Genus Chelonus Panzer, 1806

Key to the subgenera of Chelonus reported from India (modified from Zhou et al. 2022)

1. Metasomal carapace with a dorso-apical spine-like protuberance (Figs 1A, 2C); vein SR1 of fore wing sometimes incomplete (Fig. 2F); carapace with narrow straight lamella ventrally (Figs 1A, 2D, E)...................... Areselonus Braet, 1999

- Metasomal carapace without a dorso-apical spine-like protuberance [with (Figs 15C, E) or without ventro-apical tooth-like protuberances] (Figs 4C, D); vein SR1 of fore wing complete (Fig. 13A); metasomal carapace with (Figs 9A, 15D) or without (Fig. 11E) undulating lamella ventrally.................................................................... 2

2. Metasomal carapace with a pair of horns apically (Figs 7C, 9C, 12A, 15C, E)............... Megachelonus Baker, 1926

- Metasomal carapace rounded apically without horns (Figs 4D, 20C, D, 22B)...................................... 3

3. Frons deeply excavated posteriorly and smooth (Figs 3C, D); metasomal carapace very broadly truncate apically (Fig 4D) and ventral opening slightly longer than half length of carapace, opening surrounded by a lamelliform carina (Figs 4C, 4E, 5D).............................................................................. Carinichelonus Tobias, 2000

- Frons shallowly excavated posteriorly, and more or less sculptured (Figs 8C, 10C, 14C); metasomal carapace more or less narrowed apically and ventral opening usually distinctly longer than half length of carapace, and opening usually without a lamelliform carina (Figs 12B, 17D, 22A, C)................................................................ 4

4. Third tergite of metasomal carapace almost straightly narrowed posteriorly in dorsal view (Fig. 17C); apex of metasomal carapace of both sexes truncate and narrow in dorsal view (Fig. 17C) and oblique in lateral view (Fig. 17B); carapace of male deeply incurved (about one fourth of total length of carapace) in lateral view (Figs 17B, D).. Mirachelonus Zhou et al., 2022

- Third tergite of metasomal carapace hardly or not narrowed posteriorly in dorsal view (Figs 4D, 13B, 22B); apex of metasomal carapace round posteriorly or nearly so in dorsal and lateral view (Figs 4D, 13B, 22B); carapace of male gradually rounded in dorsal view (Fig. 13B)................................................................................. 5

5. Female with 16 antennomeres (Fig. 6A); carapace of male with apical opening (Fig. 12D).. Microchelonus Szépligeti, 1908

- Female with more than 16 antennomeres; carapace of male variable, usually without distinct opening.................. 6

6. Antennomeres of female 30–32 (Figs 19A, 21A); metasomal carapace of male with deep apical opening............................................................................................... Parachelonus Tobias, 1995

- Antennomeres of both sexes 17–26; metasomal carapace of male closed apically................. Chelonus Panzer, 1806