The only literature record for Hypogastrura assimilis is that of Greenslade & Fletcher (1986) who reported this species from earthworm culture boxes at Rothamsted. However, there are two specimens labelled 'Hypogastrura manubrialis' in the NHML collection from 'under cut grass' and 'hop manure' in Kew Gardens collected in the early 1960s which correspond to the description of Hypogastrura assimilis in Babenko et al. (1994) and Fjellberg (1998). The most definitive character is very difficult to see unless the mouthparts of the specimen are extruded beyond the buccal cone of the mouth. In Hypogastrura manubrialis the maxillary lamella 1 has an expanded 'double-ciliated' apex whereas in Hypogastrura assimilis, lamella 1 has only a single fringe of setae (Fig. 1). Also, there is a small papilla-like projection at the base of each lobe of the PAO in Hypogastrura assimilis (Fig. 2). There is only one clavate seta on the tibiotarsus of each foot (tt clavate setae formula 1:1:1).
Paradoxically, the few specimens labelled Hypogastrura assimilis in the NHML collection are all Hypogastrura manubrialis.