| Summary: | The promising predator Amblyseius longispinosus was revealed among phytoseiid mites from South Sakhalin and Kunashir. Different tetramychid species might be as prey for it under laboratory conditions. A. longispinosus exerted an appreciable natural con- trol of the Tetranychus' species and Amphytetranychus viennensis in field conditions. Laboratory investigations exposed thar a number of ecological parameters in A. longispinosus w a s better than those of Phytoseiulus persimilis, well-known agent in biological control. Development of A. longispinosus was completed for 3.9 days on the average at 30° C that o n e day less than developmentof Ph. persimilis under similarcon- ditions. A. longispinosus remained to be active under high levels of temperature (to 36° and its development was normal under a these conditons, whereas the temperature 35° C is critical for develooment of Ph. versimus. The gravid females A. longispinosus consumed on the average about 45 prey eggs per day (to 655 eggs per whole of female lite) and laid ni oviposition period (8-17 days) 45-57 eggs. The maximal level of reproduction w'as4 -eggsDerdav. M o r i (1969) reported A. longispinosus is a poor predacious species compared with Ph. persimilis because more adultfemales 1. urticaewere consumedb ythe latter species under similar experimental conditions. It is impossible to agree with the conclu- sion that A. longispinosus is poor predator on the whole because this predacious mite consumes more actively the• Immature stages of prey first of all, thus disturbing the age balance of tetranychid population, andthis circumstance prevents from the rapid increase in prey density and eliminates the threat of pest outbreak. From the data presented in this paper it seems conclusive that A. longispinosus is the promising predator in biological control of tetranychid mites on the greenhouse plants.
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