Naturalists have been avidly recording plants and animals in Britain for centuries. The records are usually presented as 'dot' distribution maps (e.g. Perring & Walters 1962; Sharrock 1976; Harding & Sutton 1985; Arnold 1993), which are widely used for biogeography or assessing conservation status. However, after ten years of research and attempts to interpret the mapping data, I have come to the conclusion that such dot maps have severe limitations owing to the unsystematic way in which the data are recorded (Rich 1997a, 1997b, 1998; Rich & Smith 1996; Rich & Woodruff 1990, 1992, 1996).