Isotomurus (=Isotoma = Desoria) antennalis is a scarce species whose distribution is unclear, though with a preference for wet sites, apart from one record from Kew Gardens that seems unlikely. Most records are from acid bogs in the pennines, but in 2012 Andy Murray found this species widely around Dundon in Somerset.
Isotomurus antennalis is striped, blue-purple with pale tergite boundaries (Fig. 1), quite unlike the uniform bluish-black .animal shown on p. 161 of Hopkin (2007). Fjellberg shows in nice colour photos how this species is visually almost identical to Isotomurus balteatus. The best separation is the presence/abscence of trichobothria on the body (absent in antennalis) and the layout of macrochaetae on abd 4 (see Arne Fjellberg's diagrams here). Also the mucro lacks a lateral seta.
Isotomurus antennalis is morphologically similar to other species of Isotomurus but does not have trichobothria on the body, and its taxonomic position has gone from Isotoma (eg Fjellberg 1982) via Desoria (Arbea & Jordana 1988) to Isotomurus (Popatov 2001). Popatov considered that antennalis 'obviously belongs to the genus Isotomurus in having a characteristic mucro, numerous and short setae on the body, many setae on the labium and on the posterior side of the dens'. DNA work should resolve its taxonomic position.