This very small woodlouse, reaching 2 mm, is capable of rolling into a sphere when disturbed. The head and body are covered in characteristic broad rounded tubercles (confusion only likely with Buddelundiella cataractae). However, the telson of R.costulatus has a characteristic ‘hour-glass’shape (also seen in Venezillo parvus) and it has truncated 'square' uropods typical of the familiy.
A description of this species, with figures, is given in Gregory (2014).
Distribution and Habitat
It has been collected from Kew Gardens on several occasions and recently at Eden Project (Rainforest Biome), Cornwall, where it has proved quite numerous. Additional sites are reported by Gregory & Lugg (2020).
It has been recorded in the wild in Seychelles, Mauritius, Malaysia and the Hawaiian Islands.
Gregory, S. (2014) Woodlice (Isopoda: Oniscidea) from Eden Project, Cornwall, with descriptions of species new to Britain, and poorly known British species. Bulletin of the British Myriapod & Isopod Group 27: 3-26.