Colletes balteata NYLANDER 1852; Colletes thomsoni ALFKEN 1899; Colletes sierrensis FREY-GESSNER 1903
The accompanying map is considered to be a clear representation of this species' entire distribution in Britain. It is apparently absent from Ireland. C. marginatus is a very local bee, although it is sometimes numerous where found. There is little evidence of any major decline, though in Dorset it was formerly found at Studland but was last recorded from there in 1938 (S P M Roberts, pers. comm.). A 1905 record from Swanage is shown on the map, though this specimen too is likely to have been collected nearby at Studland.