Trichoniscus provisorius Racovitza, 1908

Common name

Common Pygmy Woodouse


Trichoniscus pusillus form provisorius Racovitza, 1908
Trichoniscus pusillus ssp. provisorius Racovitza, 1908


GB IUCN status: Least Concern


This species is morphologically identical to T. pusillus sensu stricto, but is relatively smaller (gravid females rarely exceed 3.5 mm in length). It is a normal sexually reproducing species, with populations comprising approximately 50/50 male and females.

Males are readily recognised by microscopic examination of the first exopod ~ see image.

J.P. Richards
Steve Gregory
Steve Trewhella

Distribution and Habitat

This is probably a very common throughout Britain and Ireland but unfortunately most records are not differentiated between the two species (simply given as T. pusillus agg.). Verified records (based on male specimens) indicate a wide distribution throughout Britain and Ireland, but it seems more common in areas where calcareous strata occur.

It favours sunnier and/or drier situations than Trichoniscus pusillus s.str., including semi-natural limestone grassland, free-draining woodland and domestic gardens, where it can be found under stones, dead wood, etc.



Gregory, S. (2009) Distinguishing species within the Trichoniscus pusillus species aggregate, BMIG Newsletter 18: pg 2.

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



BRC Code