Irish specimens are 5-6 mm in length with a rather narrow, parallel-sided body. Coloration is mottled yellow-brown to grey-brown, appearing slightly rough to the naked eye. It is perhaps most likely to be confused with a mottled juvenile Porcellio scaber (Anderson, 2007), though the stepped body outline is more akin to the closely related Porcellionides cingendus or even Philoscia muscorum.
Distribution and Habitat
This species is only known from a one-kilometre length of sea-cliff in Co. Dublin, Ireland, where it was observed between 1909 and 1934, and was assumed extinct until its re-discovery in 2002.
In 2006-07, Roy Anderson (2007) found specimens sheltering under lichen covered rocks on steep sparsely vegetated slopes near the cliff tops. This habitat is threatened by scrub encroachment and the long-term survival of this species is in doubt.
This summary is based on the detailed account in Gregory (2009).
Anderson, R. (2007) Observations on the status and ecology of Acaeroplastes melanurus (Budde-Lund) (Crustacea: Oniscoidea) at Howth Head, Dublin. Irish Naturalists’ Journal, 28: 497-505.