The influence of different temperatures (from 26 to 39.5°C) and relative humidities (40 and 70%) on the development ofVarma jacobsoni(Oudemans) was studied by placing newly capped and parasitized worker bee broods into thermostatically controlled chambers. In one set of experiments the temperature was kept constant, and in the second set, the parasitized worker broods were placed at a temperature of 40,41, or 42°C for a time varying from 0 to 24 h and then returned to 32.5°C. The optimal temperature for development of the mites was between 32.5 and 33.4°C, which corresponds to the brood temperature ofApis melliferaL. Above 36.5°C, reproduction of varroa females was significantly reduced, and above 38°C, mites began to die without reproduction. Jumps of temperature were unfavorable to the development of the mites. The regulation of brood temperature by bees and occasional temperature peaks may be key factors in resistance of honey bees to varroa mites.