Isotomiella minor (Fig. 1) is a very common and widespread species of up to 1.3 mm in length that is invariably found in samples of soil and leaf litter. It is white in colour, does NOT possess a PAO and is eyeless. The furca is longer than the head (Fig. 1) and the mucro has three teeth (Fig. 2). The dorsal side of abd5/6 has several long 'ciliated' setae and the fourth antennal segment (ant4) bears a group of rounded sensory setae (Fig. 3). The setae on the ventral (anterior) side of the manubrium are characteristic with a 5+5 arrangement (Fig. 4).
Fig. 1 (above): Isotomiella minor of 1.3 mm in length collected from soil at Rothamsted in 1926 (collector not known).
Fig. 2 (above): Mucro (mu) with three teeth (*) of Isotomiella minor collected from Roslin in May 1937 by Bagnall. d, dens.
Fig. 3 (above): group of rounded sensory setae (*) on ant4 of the same specimen of Isotomiella minor shown in Fig. 2.
Fig. 4 (above): Isotomiella minor collected from the summit of Tryfaen, Wales by M. Davies (date not known). There are 5+5 ventral (anterior) manubrial setae (*) on the manubrium (ma). Those on the right side have fallen out leaving their vacant sockets. d, dens.
