Spatial distribution of Tyrophagus similis (Acari

We investigated the horizontal and vertical distribution of Tyrophagus similis in agricultural soils in two greenhouses between May 1997 and May 1998. Tyrophagus similis inhabited not only the cultivated soil, but also the uncultivated soil in the periphery of the cultivated area inside the greenhouse and the soil immediately outside the greenhouses. The mite density in the cultivated and peripheral soils increased in the cooler months and decreased in the warmer months. We collected only small numbers of T. similis from the adjacent outside soil during the survey period. In the cultivated soil, most T. similis inhabited soil at depths of 0-5 cm throughout the year, and their numbers decreased with depth. These results suggest that the main control point of T. similis is the 0-5-cm soil layer in cultivated and peripheral soils of the greenhouse.