The effect of prey species and stage on the life span, efficiency and fecundity of A. gossipi, was studied in an incubator at 25°C. The male usually emergee! earlier than the female but, when fed on eggs of T. urticae and E. orientalis, both sexes emergee! simultaneously. Female longevity and efficiency greatly exceeded that of the male. Mite eggs, especially those of T. urticae, induced shorter periods of predator development than did immatures; presentee! the highest total average of egg production, but the highest daily mean was observee! with immatures of C. aonidum. Adults consumee! more than 90 OJo of the prey attacked during the predator !ife span. The female of A. gossipi was most efficient during the period of egg deposition. Both of Lepidosaphes beckii and J. purchasi presentee! the !east number of preys, induced the shortest periods of the predator longevity and the least fecundity.