Reductoniscus costulatus Kesselyák, 1930

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Status:

GB IUCN status: Not applicable (non-native)

ID Difficulty

3

Identification

Reductoniscus costulatus is a very small woodlouse, reaching 2 mm body length, and is capable of rolling into a sphere when disturbed.  The head and body are covered in characteristic broad rounded tubercles (confusion is 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 family.

A brief description of this species, with figures, is given in Gregory (2014).

Andy Murray
Andy Murray
Keith Lugg
Keith Lugg
Keith Lugg
James Harding-Morris

Distribution

Reductoniscus costulatus has been collected from Kew Gardens on several occasions and more recently at Eden Project (Rainforest Biome), Cornwall, where it has proved quite numerous in 2009 and 2010, and still present in 2020 and 2024 (Gregory, 2025). A few additional sites are reported by Gregory & Lugg (2020).

Habitat

Specimens have been found beneath dead wood, among leaf-litter, peaty soil or detritus and under leaf sheaths of 'palms' and bananas. 

Elsewhere it has been recorded in 'the wild' in Seychelles, Mauritius, Malaysia and Hawaiian Islands.

References

Gregory, S.J. (2025) 15 years on: An update to Woodlice and Waterlice in Britain and Ireland, part 2 ~ Non-native species, not yet naturalised. Bulletin of the British Myriapod and Isopod Group, 37: 7-25. 

Gregory, S.J. & Lugg, K. (2020) Some recent observations of woodlice (Isopoda: Oniscidea), millipedes (Diplopoda) and centipedes (Chilopoda) from artificially heated glasshouses. Bulletin of the British Myriapod and Isopod Group, 32: 35-43. 

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.

Links

World List of Marine, Freshwater and Terrestrial Isopod Crustaceans: https://www.marinespecies.org/isopoda/aphia.php?p=taxdetails&id=262830 

BRC code

80

idBmigTaxa

Cru_1656