The Isotomurus palustris group contain some of the commonest and most widespread springtails in the UK, and can be expected almost anywhere that is permanently wet. All Isotomurus possess trichobothria on the dorsal side of the abdomen (Fig. 4). The mucro is also distinctive and has four teeth, the apical one being quite small (Fig. 5).
Their taxonomy has changed sufficiently that old records can only be put into a broad species group, and the 2007 AIDGAP key lumps at least two species under the name "Isotomurus palustris". Undoubtedly the map for Isotomurus palustris contains many literature records that refer to Isotomurus unifasciatus, Isotomurus maculatus, and other Isotomurus before they were recognised as separate species and not simply colour varieties of Isotomurus palustris.
In Isotomurus palustris sensu strictu, the central stripe is prominent and unbroken except at the dorsal margins of tergites (Fig. 1). In Isotomurus maculatus, the distribution of pigment is much more patchy, while Isotomurus unifasciatus has a totally unbroken line. The 'flanks' of Isotomurus palustris have mottled patterns, which are more prominent in Isotomurus maculatus,and totally absent in Isotomurus unifasciatus.
Isotomurus palustris is a species of wet habitats - ditches, pond edges etc (palustris means "of the marsh"), but researchers should always try to confirm the presence of trichobothria to rule out Isotoma riparia. This can be a problem after vacuum collection, which often snaps off these delicate organs.
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]