Christiansen & Bellinger (1998) suggested that all records of Sinella caeca from the UK probably refer to the closely-related species Sinella tenebricosa Folsom, 1902. The map shows the localities of the 3 Sinella 'caeca' which Steve Hopkin checked and confirmed, plus old records of "Sinella caeca". The definite sites were 'London Zoo', 'Kew hothouse' and 'Wisley, water tank'.
Sinella tenebricosa has a pointed tenant seta on the outer distal tibiotarsus (Figs. 1 and 2) - this spine is distinctly expanded at the tip in Sinella caeca. In Sinella tenebricosa, the mucronal spine reaches to the tip of the mucro, and the non-crenulated region of the dorsal side of the distal part of the dens is only slightly longer than the mucro (Fig. 3). In Sinella caeca, the mucronal spine is much shorter and the non-crenulated region of the dens much longer than in Sinella tenebricosa. Thus Sinella caeca should probably be removed from the checklist.
Sinella tenebricosa is a synanthropic species originally from the Orient which is likely to turn up in many more localities.