Trichoniscoides helveticus (Carl, 1908)

Common name

Swiss Red-eye


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

ID Difficulty



Trichoniscoides is a difficult genus and only male specimens of T. helveticus can be distinguished from T. sarsi or T. saeroeensis.  Identification is made by microscopic examination of male 2nd endopod.

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.

Theodoor Heijerman

Distribution and Habitat

First discovered in Britain in 1990 (BISG Newsletter 28, pg.2). It is known from scattered localities across central southern England, but it is likely to be considerably under-recorded; Records north of this cluster need verification. The few available records suggest it has a mutally exclusive distribution with T. sarsi (BMIG Newsletter 4, pg.1); interestingly a situation also seen in the Netherlands (Berg, 2008).

It has a strong preference for semi-natural habitats with undisturbed friable calcareous soils, including short-turf grassland, rank grassland, mixed scrub and deciduous woodland.

Specimens are typically found with difficulty by searching the underside of large stones partially embedded into soil, or from amongst chalky soil or limestone rubble.  It is often associated with other soil-dwelling trichoniscids, primarily Trichoniscus pygmaeus.
This summary is based on the detailed account in Gregory (2009).



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



BRC Code