Metatrichoniscoides is a difficult genus and only male specimens of M. celticus can be distinguished from M. leydigii or preserved specimens of Trichoniscoides. Identification is made by microscopic examination of male 2nd endopod.
Distribution and Habitat
Confirmed males are only known from south Wales and a single site in north Wales (Hughes, 2019). This woodlouse appears to be endemic to the British Isles. It is primarily associated with sparsely vegetated erosion banks occurring just above the supralittoral zone, but has also been recorded 7km inland in a limestone quarry at an altitude of 170m asl.
Characteristically, small numbers of specimens are found with extreme difficulty under large stones firmly embedded into damp humus-rich soil. It is typically associated with other trichoniscids, usually Haplophthalmus mengii, Trichoniscoides saeroeensis and Trichoniscus pygmaeus.
This summary is based on the detailed account in Gregory (2009).