Family Hydrochidae:

This family contains only four species in the genus Hydrochus Leach from India (Tables 1, 2), comprising 1.54% of the globally described diversity (276 species) (Newton 2024). Hydrochus opacus Motschulsky is reported only from the type locality. Motschulsky (1860b) contributed two species of Indian Hydrochids and Nietner (1856) and Sharp (1873), the other two species. Of the four Indian species, three are reported from the Northeast, and one each from the Gangetic Plains and Deccan Peninsula (Table 3).