Abstract
Comparative studies were made to see the effects of humidity and temperature on the breedings of three species of the grain mites, Tyrophagus dimidiatus (T.d.), Aleuroglyphus ovatus (A.o.) and Glycyphagus destructor (G. d.). In T. d., the optimum condition for the highest densities in their breeding in dried yeast was 75% in relative humidity (R. H.) and 25℃ in temperature, and the ranges of humidity and temperature to allow its breeding were relatively restricted. The optimum condition for A.o. was seen at 85% R. H. and 30℃, and the ranges were much larger, since the species was found to breed under the low humidity, or up to 35℃ under the high humidity, under which condition the former species could not survive. In G.d., the optimum was 85% R. H. and 25℃, and the velocity of the breeding was generally slower than in the former two species. Further experiments were made to compair the effects of humidity and temperature on the ratio in densities of the above three species cultured in the same food samples. The material inseminated was the mixed culture of the grain mites with A.o. as the predominant species. In all the samples kept in low humidity, or in those at 25℃ and 30℃ under various humidities, A.o. maintained the highest in the density, and all the other species were found to disappear at 30℃. At high humidity and at 20℃, either G.d. or T.d. became the dominant for certain period.
