Dispersal of diapausing T etranychus urticae and T . kanzawai

The spider mites T etranychus urticae K och and T etranychus kanzawai K ishida ( A cari: T etranychidae) overwinter mostly as mated adult diapausing females. Their overwintering survival depends in part on their dispersal towards suitable habitats. We investigated the dispersal behaviour of diapausing females of T . urticae and T . kanzawai with respect to factors known to affect the dispersal of non‐diapausing mites: light, population density, gravity, and humidity. In general, diapausing females of T . urticae showed a stronger tendency to disperse than did those of T . kanzawai under all test conditions. High population density promoted the dispersal of diapausing T . urticae , but not of T . kanzawai . Dispersal of diapausing females of both species was not significantly affected by gravity, humidity, or whether feeding damage was caused by conspecifics or heterospecifics. On plants, more T . urticae than T . kanzawai moved downward. We propose that dispersal after the onset of diapause may be an important life‐history strategy in T . urticae , but not in T . kanzawai .