Abstract
1. Under the conditions of the experiments described, Locusta migratoria migratorioides shows a preference for dry air in all parts of the humidity range, although dry air is by no means optimal for development, maturation, and breeding. 2. The strength of the reaction is correlated with the magnitude of the humidity difference available, but appears to be little dependent on the region of the humidity range. 3. The mechanism of the reaction is hygrokinetic and possibly hygrophobotactic as well, but probably not hygrotropotactic.