There is at least one species of uniformly-coloured Isotomurus that occurs in Britain and Ireland. However, there is some confusion as to its/their identity. Following work by Matty Berg in The Netherlands and Arne Fjellberg in Norway, the most likely candidates for these uniformly-coloured specimens with abdominal trichobothria are Isotomurus fucicolus and Isotomurus prasinus. There are a few scattered records in the literature for both Isotomurus palustris var fucicola and var. prasina but there are no specimens in the NHML slide collection.
Isotomurus fucicolus is uniform brownish in colour and is found in cultivated fields (farmland with manure). Reproductive males of Isotomurus fucicolus lack the dorsal lateral serrated spine setae on abd4 and abd5 that are found in Isotomurus prasinus. This is the likely identity of a brown Isotomurus that turned up in waterlogged gravel in the Pelenna river, nr Swansea, in 2010.
Isotomurus prasinus is uniform greenish in colour with some bluish on the tip of the abdomen and is very common in moist lawns (e.g. golf courses). Matty Berg has found Isotomurus prasinus to be common in the centre of a wet nutrient-poor meadow near Wageningen (Isotomurus palustris was confined to the wet ditches at the edges of the field).
There is an excellent web site on European Isotomurus by Antonio Carapelli and colleagues at the University of Siena [http://www.unisi.it/ricerca/dip/collemboli/isotopage/intro.htm]from which the picture of Isotomurus fucicolus shown in Fig. 1 is taken.