Folsomides parvulus is a rare species with a very distinctive body shape (Fig. 1). It is white in life, has 2+2 ocelli (Fig. 2), and a mucro with two teeth fused to the dens which has 3 dorsal setae (Fig. 3). There is one slide in the NHML collection bearing the Hartland Moor specimen), and individuals collected by Peter Shaw from a chalk quarry on Box Hill in Surrey were confirmed as this species by Steve Hopkin. The other literature records are from a chalk quarry in Yorkshire (Parr, 1978) and (oddly) manure in the rose garden at Kew Gardens (Lawrence, 1967).
There is a second Folsomides on the UK/Irish list, Folsomides angularis, for which 2 reports exist. Peter Lawrence recorded one from the Burren, Ireland, without comment or detail. Bagnall (1939) supplied a convincing description of a Folsomides with 5 eyes from Whitley Bay, Northumberland. None of these specimen survives, leaving Folsomides angularis as a UK species in need of confirmation. Its distinguishing features are 5 eyes, absence of ventral manubrial setae, 2-toothed mucro and clear angulation of the hind body.
Folsomides sp. are well-known for their ability to withstand extreme dryness and can survive for long periods in a cryptobiotic state. Belgnaoui & Barra (1989) found that Folsomides angularis could not regulate its water loss better than other Collembola, but once dessicated could survive relatively high temperatures as well as cooling to -180C. This probably explains the tendency of this genus to turn up in the hot, thin soil of chalk quarries. At least Folsomides parvulus is probably widespread but thinly spread in the UK in the hotter and drier of our soils and sand dunes.