LAUSR

The Hymenoptera (Aculeata) fauna was studied in birch stands (Betula pendula Roth) of colder areas of Northern Bohemia using the method of Moericke's yellow traps. Altogether 159 species were trapped; the most important were Andrena lappona, Vespula vulgaris, Halictus sp., Trypoxylon minus and Vespula rufa. Only 12.7% of the species are widely spread in this ecosystem type. In 1990-1994 and in 1995-1999 we compared the abundance of the fauna and discovered that many species of the families Apidae and Sphecidae receded from the birch stands due to changing site conditions (light, weed infestation).