Casing natural geographical boundaries, 130 spp. can be considered as European, though when broader political borders are followed this number rises to 136. In addition 20 exotic spp, have been recorded as a result of accidental importation. The highest diversity, defined by the number of spp. per standard area of 250x250 km2, is found in the Alps, while the lowest diversity occurs in the northern parts of mainland Europe and on some islands. Surprisingly, the Mediterranean region is not as rich in spp. as the central part of Europe. When compared with other continents, it is clear that Europe has the lowest number of spp. However, when compared specifically with areas at the same latitude, the Odon. diversity in Europe is relatively average: somewhat higher than expected in the northern regions, somewhat lower than expected in southern regions.