The distribution of this species is significantly different from that published by Richards (1980), due to the separation in Britain of two species, T. nitidus and T. unicolor from the one taxon previously recognised as T. unicolor.
There is considerable confusion regarding the correct use of this name. As interpreted here this is the scarcer species of the two, apparently restricted to IOW and Dorset.
This species has a distribution apparently restricted to the south coast of the Isle of Wight and some places on the Dorset coast. It also occurs in the Channel Islands on Guernsey and Jersey. Overseas the species is widespread in the Palaearctic.