The developmental success and the oviposition of the Kanzawa spider mite, Tetranychus kanzawai KISHIDA, on 44 species of plants were studied for four populations collected from tea, pear, hydrangea and kudzu vine. Of the plants tested, 14 were common hosts of the four populations. The tea plant was utilized only by the tea population, and the hydrangea plants only by the pear and hydrangea populations. These three populations could utilize the kerria plant, while the kudzu population could not. In intrapopulation crosses, all populations produced both female and male progeny. Inter population crosses among the three (tea, pear and hydrangea) populations were successful. However, female mites of the kudzu population were reproductively incompatible with males from all of the other populations. Thus, it was concluded that T. kanzawai consists of the tea-associated, the hydrangea-associated (pear and hydrangea), and the kerria-avoiding (kudzu) populations. In addition, the kudzu population was determined to differ in reproductive traits from the other populations.