Trichoniscoides sarsi Patience, 1908

Common name

Sars' Red-eye


Trichoniscoides sarsi sensu stricto
Trichoniscoides sarsi seg.


GB IUCN status: Least Concern
GB rarity status: Nationally Scarce

ID Difficulty



Trichoniscoides is a difficult genus and only male specimens of T. sarsi can be distinguished from T. helveticus or T. saeroeensis.  Males of T. sarsi are readily separated from other British species of Trichoniscoides by the presence of a hooked projection at the base of the merus of the 7th pereiopod.

All three are small (to 4 mm) creamy-white woodlice flushed with varying amounts of orange.  The dorsal surface is covered with weak tubercles and the eye is composed of a single dark red ommatidum.  All eye and body pigments are rapidly lost in alcohol, thus making preserved specimens difficult to separate from Metatrichoniscoides celticus or M. leydigii.

J.P. Richards
J.P. Richards
J.P. Richards
J.P. Richards
J.P. Richards
J.P. Richards
Nicola Garnham
Nicola Garnham

Distribution and Habitat

The scattered records form a distinct band across eastern and central England, and into eastern Ireland.  The few available records suggest it has a mutally exclusive distribution with T. helveticus (BMIG Newsletter 4, pg.1); interestingly a situation also seen in the Netherlands (Berg, 2008). Characteristically, it is associated with synanthropic sites, such as old gardens or churchyards (e.g. Richards, 2016), but some coastal sites in Kent and south-west England appear to be semi-natural (e.g. Gregory, 2012; Ashwood & Gregory, 2021). In 2010 specimens were collected from a coastal site in eastern Scotland (BMIG Newsletter 22, pg.2).
Specimens are usually found beneath paving slabs or stone partially embedded into the soil, but it also may be found among soil or rubble. It is elusive, rarely found in large numbers and probably under-recorded.  It often occurs with other trichoniscids, such as Trichoniscus pygmaeus, Haplophthalmus mengii and Trichoniscoides albidus.
This summary is based on the detailed account in Gregory (2009).



Gregory, S.J. (2012) The occurrence of two elusive woodlice, Metatrichoniscoides leydigii (Weber, 1880) and Trichoniscoides sarsi Patience 1908, in semi-natural habitat in Kent. BMIG Bulletin 26.37-40.

Gregory, S. (2009) Woodlice and Waterlice (Isopoda: Oniscidea & Asellota) in Britain and Ireland.  Field Studies Council/Centre for Ecology & Hydrology.



BRC Code