In a laboratory experiment, the influence of air humidity on ticks of known calendar age was investigated. In desiccators at different humidities (44%, 55%, 70%, 84%, and 98%), we studied changes in the life span and development of eggs, hungry and fed larvae, nymphs, and adult ticks Ixodes persulcatus and I. ricinus. It was found that changes in air humidity at temperatures comfortable for ticks determine the lifetime of hungry ticks waiting for the host, the possibility of molting at the next stages, and the preservation of egg clutches. 84–98% humidity is ideal for the survival of hungry and fed larvae, nymphs, adult ticks, and egg clutches. A decrease in humidity to 70% for a month leads to a significant population reduction. Humidity of 40–55% is fatal for I. persulcatus after 10–15 days. At 40–55% air humidity, an insignificant part of the populations of I. ricinus survives for up to 1 month with a complete death of clutches.