Isotomurus plumosus was described as a new species by Bagnall (1940) from sites in the Hebrides and northern England. It is has a distinct colour pattern consisting of a yellowish ground, a prominent central dark stripe and a lateral stripe on each side of the body (Fig. 1). A full description is included in Stach's (1947) monograph under the name Isotomurus palustroides form subciliatus. The mucro has a lamella and a mucronal seta (Fig. 2; absent in Isotomurus palustris). In addition, the short setae on the abdomen are 'ciliated' at the base.
Isotomurus plumosus has a scarce, but widespread distribution and should be looked for in wet habitats everywhere. A few early records of Isotomurus 'aquatilis' Muller and Isotomurus 'trifasciatus' Bourlet probably refer to this species but no types have survived to enable this to be confirmed.
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]