Philoscia affinis Verhoeff, 1908

Distribution

In Britain and Ireland this native woodlouse has been over-looked  (with specimens simply dismissed as 'P. muscorum') and could prove to be frequent and widespread, at least in western areas, if specimens are given a second glance. 

The presence of Philoscia affinis in the UK was first confirmed in south-east England in summer 2017 (Segers, Boeraeve & De Smedt, 2018). Subsequently, specimens previously mis-identified as P. muscorum that were collected in 2004 in South Wales and in 2006 from Oban, western Scotland, were re-identified as Philoscia affinis. Recent field work has discovered many additional sites, mainly in western Britain, including North Wales (Hughes, 2019), Lancashire, western Scotland  (Gregory, 2020) and Northern Ireland (Anderson, 2019). In 2023 it was recorded from the well-worked Isles of Scilly where previous surveys had only noted P. muscorum. An updated distribution map is given in Gregory (2024) pg 24.

Habitat

Philoscia affinis has a preference for rural sites, such as open woodland and rank coastal grassland (in contrast P. muscorum generally favours open grassland sites). It does not favour synathropic sites such as churchyards and gardens (in which P. muscorum thrives). However, there are a few recent records (BMIG Newsletter 47, 2023, pg 8 & 11; Gregory (2024)) from garden centres and a city centre raised ornamental  street planter suggesting that it may spread further afield via the horticultural trade.

It can be found under stones and dead wood, or among accumulations of leaf-litter. 

This summary is based on Gregory, 2020, updated in Gregory (2024).