This is a dark purplish-red species, capable of rapid movement, somewhat reminiscent of a large Trichoniscus pusillus. However, it differs in the eye being composed of a single prominent ommatidium and both eye and body pigments fade in alcohol to a pale straw colour (T. pusillus has three ommatidia and body pigments are retained).
Distribution and Habitat
This species is virtually confined to Ireland, where it is locally common across much of the south-east.
It was unknown in Britain until 1994 when a site was discovered in south Wales. In 2010 a population was discovered in Mid-Lothian, Scotland (Sivell & Gregory, 2012) and a detailed account of its occurrence there is given by (Maguire, 2020).
It is characteristically associated with river and stream valleys, often inhabiting rough vegetation beside watercourses, where it occurs among leaf litter, under stones and dead wood.
This summary is based on the detailed account in Gregory (2009).
Maguire, W. (2020) The distribution of Oritoniscus flavus (Budde-Lund 1906) in VC83 Midlothian (Isopoda: Oniscidea: Trichoniscidae) Bulletin of the British Myriapod & Isopod Group 32: 59-64.
Sivell, D. & Gregory, S.J. (2012) Oritoniscus flavus - a woodlouse new to Scotland. Bulletin of the British Myriapod & Isopod Group 28: 44-49.
Gregory, S. (2009) Woodlice and Waterlice (Isopoda: Oniscidea & Asellota) in Britain and Ireland. Field Studies Council/Centre for Ecology & Hydrology.