Recent investigations on the control of cheese mites in New Zealand have necessitated detailed biological studies of the species concerned. Experiments have been carried out on the physical ecology of the species, Tyrophagus longior, Gerv., Tyrolichus casei, Oudm. [Tyroglyphus siro, auct.] and Tyroglyphus farinae, Degeer. A technique has been developed whereby, under controlled temperature and humidity conditions, individual developmental records may be readily obtained for all stages of the life-cycle. This technique is one that may be modified for similar studies on small insects, such as Thysanoptera, Collembola, etc.