Proisotoma tenella is a rare greyish species that reaches 1.0 mm in length. The only published record is that of Carpenter (1908) who found it feeding on tobacco plants in Ireland (its presence on bulbs is also mentioned). However, there is a slide in the NHML with specimens of Proisotoma collected from 'mushrooms' in Penrhyn, Bangor, North Wales. Most of the Collembola on the slide are Proisotoma minuta. However mixed among them is at least one specimen of Proisotoma tenella with 8+8 ocelli, 3+3 ventral manubrial setae, numerous setae on the ventral side of the dens and mucro with two teeth (Fig. 1). These key out in Potapov's (2001) Synopsis as Proisotoma tenella. Its habitat suggests that these were introduced from warmer climes, yet another member of the 'tramp species' of 'Proisotoma'!

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Fig. 1 (above): Furca of Proisotoma tenella collected from 'mushrooms' at Penrhyn, Bangor in North Wales in February 1936 by W.M. Davies. The specimen is not in brilliant condition but the 3+3 ventral manubrial setae (*) are clearly visible. The mucro has two teeth and the ventral side of the dens bears many setae.