*poseidonis Bagnall, 1939
Friesea mirabilis is a bluish-grey very common and widespread soil-dwelling species with three anal spines (Fig. 1). The largest specimen Steven checked was 1.3 mm in length although the species may reach 1.9 mm according to other authors. Friesea mirabilis does not possess clavate setae and the dens bears a small mucro (Fig. 2; the main feature which separates it from Friesea truncata).
Some authors use chaetotaxy to separate Friesea mirabilis from Friesea truncata. Friesea mirabilis has been described as having seta a4 PRESENT on the dorsal side of the second thoracic segment (th2) whereas in Friesea truncata, seta a4 is ABSENT from th2. In Friesea mirabilis, seta A4 is supposed to be PRESENT on the tibiotarsi whereas in Friesea truncata seta A4 is ABSENT. However, these characters are not 100% reliable in UK/Eire material I have seen; asymmetry is frequent. The possibility still exists that Friesea truncata is simply a variety of Friesea mirabilis.
Species of Friesea have 8+8 ocelli (Fig. 3) but no post antennal organ (PAO) or empodium on the foot (Fig. 4). The mandibles are reduced (as in all Neanuridae) and do not bear a grinding plate (Fig. 5).
Several of the records by Bagnall were made under the name Friesea poseidonis which is a junior synonym of Friesea mirabilis.