In the present study, we evaluated and compared the in vitro biological parameters of the evolutionary stages of R. microplus (female, eggs, and larva) from two extreme regions of Brazil: Santa Rita (SR) northeast region and Bagé (BG) southern region. For this, all stages were maintained at 23, 27, and 32°C with a relative humidity (RH) of 65, 80, and 100%. The mean incubation period was 43.7 to 53.7 days (SR population) and 59.0 to 56.1 days (BG population) at 23°C and 18.0 to 19.3 days (SR population) and 16.8 to 21.2 days (BG population) at 32°C. Eggs incubated at 23°C (65, 80, and 100% RH) of SR and BG populations showed a similar egg hatching percentage (P > 0.05). The egg hatching percentage of the SR population (30.5 to 98.0%) was always higher than that of the BG population (8.7 to 85.5%; P < 0.05) when incubated at 32°C and 65, 80, or 100% RH. Deleterious effects on the larval survival period from SR and BG were observed under all experimental conditions (temperature and RH), especially at 23 and 32°C. However, they were more intense on larvae at 32°C (all RH). Under 80 and 100% RH, the mean period of larval survival did not exceed 65 days, being shortest for the BG population (mean: 42.7 days [80% RH] and 55.1 days [100% RH]) compared with the SR population.