Proasellus meridianus (Racovitza, 1919)
GB IUCN status: Least Concern
Proasellus meridianus can usually by distinguished from Asellus aquaticus by the continuous pale band along the posterior margin of the head. However, care is needed since in some specimens the dark gut can be seen through the pale head giving an impression of a pigmented patch. Consequently the the two species are frequently confused. The shape of the male first pereopod is diagnostic.
P. meridianus occurs throughout Britain (but under-recorded in Wales and Scotland). In many areas it is much less frequently recorded than A. aquaticus. There are very few, mostly old, Irish records, again perhaps reflecting under-recording.
Although found in similar places to A. aquaticus, among water plants, under stones and submerged bits of dead wood, etc, it is rarely found in garden ponds and is much less tolerant of pollution.
This summary is based on the detailed account in Gregory (2009).