It appears that 25 species have become extinct in Britain, although we cannot be certain as to the accuracy or extent of historical records. In addition, species previously considered extinct can sometimes be rediscovered following periods without records.
A re-introduction project is underway for one species of Bombus (details below).
Records cannot always paint a full and accurate picture. The gathering of records requires sufficiently trained persons across locations, to collect such data. This has not always been possible, and amateur records cannot always be verified.
Nevertheless, as I write in 2021, the records currently suggest the picture described below, but this may change. This website also has a page listing UK BAP (Priority List) species.
The date of the last recorded siting is listed in brackets:
Bombus subterraneus - the short-haired bumble bee, was last recorded in 1988, and declared regionally extinct in the year 2000.
This species was once widespread in Britain. It is believed that farming practices, habitat loss and agro-chemical were responsible for the loss.
In 2007, Natural England proposed that this species be reintroduced to the UK, with the intention that sustainable populations could once again become established in Britain.
A full disease risk analysis was carried out for using queens sourced from Sweden in 2011, following unsuccessful attempts to source queens and rear colonies from New Zealand.