Ballistura filifera appears to be native to Central and South America and has clearly been introduced. The only confirmed records are from mushroom and cucumber beds. It was also found by Greenslade and Fletcher (1986) in earthworm-rearing beds at Rothamsted but is now presumably extinct there. Ballistura filifera is greyish blue, up to 0.9 mm in length and has a distinctive set of characters shown in Figs. 1 to 5 below including 6+6 ocelli, a very long mucro, and a clear empodial filament. The three specimens in the NHML slide collection that Steve Hopkin found corresponding to this description were mis-identified as Proisotoma minuta, Ballistura borealis and Pachyotoma ultonica (!) Ballistura filifera may be present in many more localities where levels of organic matter are high and there is protection from frost.
There are 2 other Ballisturas that have turned up in the UK and are keyed out in the AIDGAP key (Hopkin, 2007): Ballistura ultonica and Ballistura fitchi.
Ballistura fitchi was originally described from Costa Rica, but has been found to be abundant in glasshouses in several countries. The only record for Ballistura fitchi in UK/Eire was made by Greenslade and Fletcher (1986) from earthworm-rearing beds at Rothamsted where it is now probably extinct, and no preserved specimens survive. Ballistura fitchi differs from Ballistura filifera by having 8+8 ocelli, tibiotarsus of foot with two long tenant setae with one of them clavate (all pointed in Ballistura filifera) and no filament at the end of the empodium of the foot (present in Ballistura filifera). In addition, Ballistura fitchi has only one ventral (anterior) seta on the dens (three in Ballistura filifera).
Ballistura ultonica was described by Carpenter (1911) as new to science from specimens collected in garden soil from Ballyclare, County Antrim. Unfortunately, no type specimens appear to have survived, but the description fits a species of Ballistura (8+8 ocelli, very long mucro, absence of apical ventral manubrial setae, one ventral seta on dens, empodium with a filament, tenaculum with 4+4 teeth). It seems to possess characters of both Ballistura filifera and Ballistura fitchi, but does not exactly match either. It is possible that 'ultonica' was an introduced species of Ballistura that could subsequently have been described as new to science from another country (or not at all). There are a few scattered literature records, mainly from Ireland but the identity of these is impossible to confirm unless specimens can be found.