The basic ecological characteristics of Tetranychus okinawanus Ehara, a new spider mite speciesf rom Okinawa Islands, were examined and compared with those of other tetranychid mites. The mites develop more quickly and lay more eggs at young ages than other typical colonizing speciesuch as T. urticae and T. kanzawai. Thus, T. okinawanus has the highest intrinsic rate of natural increase among tetranychid mites reported so far. The mites lack diapause capacity and do not survive well at low temperatures. However, the polyphagous nature and the extremely highreproductive capacity of T. okinawanus may potentially enable it to be a serious pest in controlled environments such as greenhouses.

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Mochizuki, M . and A. Takafuji, 1996. Effect of photoperiod and temperature on the diapause termination of the Kanzawa spider mite, Tetranychus kanzawai Kishida(Acari: Tetranychidae). J. Acarol. Soc. Jpn., 5(2): 83-88.
Reproductive diapause of the adult females of the Kyoto population of Tetranychus kanzawai induced under laboratory conditions ended much faster under long-day(16L8D)than under short-day(9L15D). Temperature also played a part; the diapause ended quicker at 20°C than at 15°C. The majority of females did not require any chilling for diapause termination. These results suggested that the diapause intensity of T. kanzawai in central Japan was weak and short-days maintained diapause. Overwintering adult females collected from a tea field in Shizuoka gradually lost sensitivity to short-days after December. More than half of the females collected in late December started oviposition within about 10 days when exposed to both short-days and tolong-days. This result indicated that the diapause of T. kanzawai had ended by mid-winter.

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Gotoh, T., A. Takafuji and K. Gomi, 1996. Tetranychid mites of Okinawa Island(Acari: Tetranychidae). J. Acarol. Soc. Jpn., 5(2): 89-94.
This study was undertaken to elucidate: 1)the spider mite fauna of Okinawa Island and the occurrence of Tetranychus okinawanus, a newly described species from the Ryukyu Islands, 2)whether populations of T. kanzawai from the Island are one of two previously described strains, the kerria strain or the kerria-avoiding strain, and3)whether populations of T. pueraricola from Okinawa and Honshu are conspecific. Six species of tetranychid mites(T. urticae(green form), T. okinawanus, T. piercei, T. pueraricola, T. kanzawai and Oligonychus biharensis)were collected from 13 different plants. T. okinawanus was not found on agricultural crops in the present survey, but was abundant on weeds. Crossing experiments revealed that all seven populations of T. kanzawai collected from seven plant species were the kerria strain. There was a strong reproductive incompatibility between the Nago and Hitachi-Ohta(Ibaraki Pref.)populations of T. pueraricola, but the mechanism responsible for the incompatibility was unknown.

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