none. Over seven years of observations in two localities in central Bohemia (Czech Republic, Praze-Ruzyni & Zlonicich), ten species of hymenopterous parasitoids were reared from cocoons of the cereal leaf beetle (O. galleciana Heyd., syn. O. lichenis Voet). They included five species of the family Ichneumonidae, viz., Bathytrix maculatus, Gelis instabilis, Lemophagus curtus, Itoplectis alternans, I. maculator and Scambus annulatus; four species of the family Pteromalidae, viz., Pteromalus chrysos, P. semotus, P. vibulenus and Trichomalopsis microptera; and one species of the family Eulophidae viz., Necremnus leucarthros. In a locality intensively used for growing cereal crops, the parasitoid spectrum was poorer, lacking three of the species. Necremnus leucarthros, a gregarious plurivoltine species, was dominant. The parasitization by this species varied between 3 and 39.2% in successive years of study. Gelis instabilis and Pteromalus vibulenus were subdominant parasitoids. Gelis instabilis is a hyperparasitic ichneumonid which, in the course of the seven years, emerged from 0.8 to 8.1% of cocoons. At the same time, Pteromalus vibulenus parasitized 0 to 6.6% of cocoons. The remaining plurivoltine parasitoids emerged only singly, as the cereal leaf beetle was only a minor intermediary host for them. Necremnus leucarthros, showing the highest percentage parasitization of cocoons, was the only parasitoid capable of significantly affecting the population dynamics of the cereal leaf beetle. The degree of infestation of the leaf beetle cocoons was influenced by the plant community growing in the vicinity of winter wheat crops. In a varied landscape comprising ecological corridors the parasitization was twice as high as in a landscape intensively used for growing cereal crops, almost devoid of areas grown wild-growing plants.