Mesentotoma dollfusi is an apparently scarce species which is only found close to the sea (the locality from Grange about 30 km west of Dublin is from Tom Bolger's (1986) Irish Checklist; the record is sourced from an unpublished MSc thesis and is unlikely to be correct). The map suggests that Mesentotoma dollfusi might be restricted to Ireland and Southwest England although there are too few records to draw any firm conclusions.
The pigmentation on the body is distinctive (Figs. 1 and 2). The specimens in the photographs were collected from just above the high tide mark in strand line debris on Crackington Haven beach on the north coast of Cornwall in September 2001.
In April 2004, Steve found a specimen of this species being eaten by a jumping spider Salticus scenicus under a stone on the beach at Lowland Point near Coverack on the Lizard Peninsula in Cornwall, and considered that it is probably present in every coastal hectad in Cornwall and Devon.
Mesentotoma dollfusi used to be placed in the genus Entomobrya, which it clearly resembles. However Mesentotoma dollfusi lacks the basal spine on the mucro possessed by all species of Entomobrya.