Abstract
We let straws piled up and rot in the field, and investigated occurrence of acarid mites on them and fresh ones of rice. As a result, the number of acarid mites (Tyrophagus putrescentiae (Schrank)) reached its peak two months later, and decreased three months later on both straws. The number on the rotten straws was less than fresh straws. Then, we bred Tyrophagus similis Volgin by the rotten straws for 28 days at 24°C, 14L10D, starting with 20 mites. While the number of acarid mites on fresh straws amounted to about 1000 to 3700, it was 150 to 200 on rotten straws piled for three months. It may be possible to control their number by using rotten straws instead of fresh straws.
