ABSTRACT.A circular humidity gradient apparatus with a porous cellulose substrate was used to compare the humidity responses of pseudoworkers (immature wood‐feeding forms) of five species of dry‐wood termites. Four of these species are widely distributed pests of buildings:Cryptotermes brevis(Walker),C. cynocephalusLight,C. dudleyiBanks andC. havilandi(Sjöstedt). The fifth species,C. naudeiCoaton, has not been recorded from buildings.C. havilandi, C. cynocephalusandC. naudeiwere found to tend to group and feed at humidites above 90% r.h., whileC. dudleyipseudoworkers avoided humidities above 90% r.h. and below 70% r.h. These results accord with the results of studies on the effects of relative humidity on feeding and reproduction of these species. The behaviour of the most widespread species,C. brevis, seems to be closely associated with its ability to undergo acclimatization and to feed efficiently at either medium (c.60%) or high (c.90%) relative humidity.C. breviskept at 89% r.h. showed an increased tendency to group at humidities above 90%, with a lower temperature preference, changes in faecal pellet formation and, for one population at least, an increased tolerance of exposure to saturated air. The humidity preferences at constant temperature were compared with the temperature preferences of the same individuals examined in uniform humidity. The value of behavioural responses as indicators of physiological differences between species and populations is consid