Some physiological responses to temperature changes of Petenia kraussii subjected to several acclimation temperatures (21, 23, 27, 30 and 33°C) are described. The thermal strength was measured by the methods of Critical Thermal Maximum (Minimum) (MTC), Median Letal Temperature (TLM) and Upper Incipient Lethal Temperature (UTLI). The results obtained in each method used showed that acclimation temperature influences directly on thermal tolerance.