Armadillidium vulgare (Latreille, 1804)
GB IUCN status: Least Concern
Our seven Armadillidium species and Eluma caelata (Family Armadillidiidae) are readily recognised in the field by their truncated 'square' uropods that end flush with the body and their ability to roll into a protective sphere (similar truncated uropods are also seen in the non-native Armadillidae species).
Armadillidium vulgare is the common large pill-woodlouse (to 18 mm body length). Although often uniform slate grey, it can be highly variable in colour and mottled forms are often seen. However, it lacks the diagnostic contrasting dark patch on the 7th epimera, and the well developed ornate mottling, characteristic of the uncommon A. pulchellum or A. pictum. See Gregory & Richards (2008) for details of the identification of these three species.
In south Wales and southern England it can be confused with A. depressum (which can be locally common in gardens, etc).
This species is locally abundant in south-eastern England, but becomes much scarcer further north and restricted to lowland sites with calcareous soils and high levels of insolation. Scottish sites are mostly coastal, where it occurs as far north as Aberdeenshire (Davidson, 2010). In Ireland there is a wide scatter of records with a distinct south-east bias.
[The record shown from the northern Scottish coast on the NBN map is erroneous.]
It occurs in a wide variety of habitats both inland and coastal; woodland, grassland, gardens, etc. It is most easily found under stones and dead wood, but also amongst grass litter, within tussocks, etc.
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.
Gregory, S. & Richards, P. (2008) Comparison of three often mis-identified species of pill-woodlouse Armadillidium (Isopoda: Oniscidea). Bulletin of the British Myriapod & Isopod Group, 23: 9-12.