Until recently, Folsomia diplophthalma was characterised as being white with 1+1 ocelli and 1+1 apical setae on the ventral (anterior) side of the manubrium. However, this species was re-described by Potapov & Dunger (2000) who examined Axelson's holotype. They discovered that the manubrium of Folsomia diplophthalma usually has 4+4 apical ventral (anterior) setae arranged longitudinally (the complete range is from 2+3 to 6+6, but never 1+1).
     Potapov & Babenko (2000) described the new species Folsomia palaearctica with 1+1 ocelli and 1+1 apical setae on the ventral (anterior) side of the manubrium. In theory, records for Folsomia 'diplophthalma' in Britain and Ireland could be Folsomia palaearctica. However, the posterior pair of ocelli in cleared specimens are often very difficult to see. At least some of the specimens of Folsomia 'diplophthalma' in the NHML collection have 2+2 ocelli (a pair of tiny posterior ocelli can be discerned at 1000X magnification under phase contrast lighting) and these key out as Folsomia quadrioculata or Folsomia manolachei. Thus, the presence in Britain and Ireland of Folsomia diplophthalma sensu Potapov & Dunger needs to be confirmed (and is unlikely).
     However, Folsomia diplophthalma sensu Potapov & Dunger is almost identical with Folsomia similis Bagnall, 1939 (Folsomia diplophthalma has 4+4 laterodistal setae on the ventral tube and lateral teeth on the claws whereas Folsomia similis has only 3+3 laterodistal setae on the ventral tube and no lateral teeth on the claws). It is probably best to retain them as separate species for the present, but it is possible that Folsomia similis may eventually be sunk as a junior synonym under a broader definition of Folsomia diplophthalma.

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