OLIGOLECTIC BEE SPECIES IN NORTHERN EUROPE (HYMENOPTERA, APOIDEA)

Evolution of flower specialization in bees, the concepts of poly-, oli go- and monolecty are reviewed. About 60 species recorded in the area of Finland and Sweden are regarded as oligolectic. The proportions of oligoleges among all pollen-collecting bee species are about 30 percen t in a large area of central and Northern Europe. The proportion is ab out 15 percent in the northern boreal area of Finland and Sweden, wher e the percentage of polylectic bumblebees is much greater than in more southern areas. Of the solitary bee species recorded in Finland and S weden, 25 are regarded as narrow oligoleges, of which 6 species collec t pollen from Campanula and 5 from Salix. Eusocial Bombus consobrinus is regarded as a facultative narrow oligolege of Aconitum septentriona le and, apparently, this bee species is the only oligolege in northern Europe, whose distribution completely covers that of the pollen plant . The distribution limits of some narrow oligoleges (e.g. Eucera longi cornis and Andrena hattorfiana) approximately follow certain frequenci es of their principal pollen plants (Lathyrus pratensis and Knautia, r espectively). Of the oligolectic bee species in Finland, 32 occur on t he lists of threatened species of England, southwestern Germany or Pol and. Records of E. longicornis and A. hattorfiana from various periods are given as examples of the decline of oligolectic bees in Finland d uring recent decades.