“…cricetus is capable of mass multiplication (outbreak). This is probably promoted by favourable climatic conditions, such as rainless, warm weather (GRULICH, 1973, MANNINGER and KACSO, 1961, PETZSCH, 1950, TOTH, 1974, or by manmade conditions: removal of the detrimental effects of floods, a low ground water level and changes in agricultural technology (GRULICH, 1973, KOVACS and SZABO, 1971, PETZSCH and PETZSCH, 1968, TOTH, 1974. Levels of 30-50 (HUBERT.…”