Osmia fuciformis LATREILLE 1811; Osmia chrysomelina PANZER 18112; Osmia atricapilla CURTIS 1828; Osmia pyrenaica LEPELETIER 1841
Of the 24 species of endangered bees listed in the British Red Data Book (Shirt, 1987), four have only been recorded in recent years from a single site. One of these is Osmia xanthomelana, the largest and perhaps the most attractive of the ten species of British Osmia.
The map illustrates the former widespread distribution of this species in Britain, from the south coast northwards to Tyneside. It has been recorded from about 28 widely scattered localities (Else, 1994b). Throughout this century there has been a contraction of this range southwards, so that currently the species is on the verge of extinction. The mapped data for the Isle of Wight represent the known nesting location and a single specimen from the south side of Sandown Bay. The population there in most years is estimated to consist of a few tens of individuals, though daily totals of individuals seen are considerably less (Else, 1994b). Some apparently ideal sites in north Wales for the species were investigated in 1994 and 1995 by C Clee, but unfortunately without success. The cause of this considerable decline is unknown but may possibly be a combination of loss of suitable habitat and climatic changes. The bee is also rare elsewhere in Europe.