Abstract
Results of an experiment reported previously (Rivard, 1958a) showed the influence of various humidities on mortality and rate of development of the immature stages of Tyrophagus castellanii (Hirst)reared on mould cultures at a constant temperature. Results of an experiment on the influence of humidity on the longevity and fecundity of the adult mites are reported in the present paper. Information gathered from both studies is used to calculate the innate capacity of the species for increase at different humidities.