Ratnadvipia karui is restricted to the lowland rainforests of the wet southwestern corner of Sri Lanka, the so-called wet zone (Raheem and Naggs, 2006). Ratnadvipia karui occurs at elevations ranging from 55 - 938m (Raheem et al., 2009).
Distribution of Ratnadvipia karui (dark orange shading) and R. irradians (pale orange shading) in Sri Lanka in relation to natural forest cover (solid grey shading). The wet zone is delimited by the 2500 mm isohyet and the 1800 mm isohyet separates the intermediate and dry zones. Source for forest cover and rainfall data: Legg and Jewell (1992, 1995).
The other members of the genus, Ratnadvipia irradians have a range encompassing all of the known range of Ratnadvipia karui, and in the field the two species can often be observed together.
Ratnadvipia irradians is distributed across almost all of the wet zone, and also extends into the wetter or more elevated parts of the intermediate and dry zones (Raheem and Naggs, 2006).
Ratnadvipia irradians has a wide elevational range (50 -1961m, Raheem et al., 2009), and unlike Ratnadvipia karui occurs in both natural forest and cultivated habitats (e.g. village home gardens).