Studies on acaroid mites I : Ecological studies on the acaroid (tyroglyphid) mites, Tyrophagus dimidiatus (Hermann, 1804)

Abstract

Mass rearing of Tyrophagus dimidiatus under the laboratory condition has been succeeded by the author and during his studies on the relations of breeding or longevity to environmental factors, especially temperature and humidity, some new notes were observed. These notes are summarized as follows : 1. Relations between breeding and temperature or humidity were studied using chocolate, cheese, and rice as food of mites. The most suitable relative humidity range is 75 to 84% under 25℃. The range is thus limited, even taking differences of results obtained by state or water contents of foods into consideration. 2. The results obtained by the experiment using microscopic-heater and thermo-couple shows that the resistance of the mites against high temperature is relatively weak, i. e. temperature range over 35℃ is fatal and temperature of 47° and of 50℃ kills them immediately. 3. Influences of low temperature were observed on breeding rate and longevity. Neither breeding nor activity are observed under 1° to 5℃, 76% R. H., and survival rate after 5 weeks is 25% and 67.6% of those are deutonymphs. Thus resistance of deutonymph against low temperature is remarkablly strong and this stage may be suitable one overwintering of this mite. 4. Experiment using glass capillary with several saturated salts in both ends to keep several humidity needed was carried out. The results show that most of mites chooses 75 to 80% R. H. 5. From the result obtained by the observations on breeding and development stages using cheese as food under 75 R. H., the phenomena in which colony under new environment increased in number of young stages after 3 weeks, formed matured colony after 25 days. reached under equivalent state after one month, and then gradually became infirm were observed. 6. Weight of one gram matured colony contains 104, 947 individuals.