Common-land-system is characterized by the use of common land for animal breeding and grazing. Current paper is fine-tuned to the occurrences of grasshopper infestation and swine fever within the communal land system in the 1940s in the region of Irati PR Brazil. Investigation focuses on the practice and meanings of common land users appropriated by the above-mentioned occurrences since the latter tested the common land system and the survival and permanence of its users in the region. [ABSTRACT FROM AUTHOR]