Known for a long time to applied biologists for importance of parasitoids in regulating the population densities of scale insects. The author has spent ore than five years researching biological control, visiting and studying the efficiency of certian parasitoids for controlling San Jose scale and lataniae scale. The author during his study has been visited Austria throughout study grant for two years "as an original habitat for the new invasive pest to Egyptian farmlands, SJS, without its specific natural enemies" to compare the role of native parasitoids with the local parasitoids. The author discuss therotical approaches and specific experiments in pest control. The monograph it has assemled will interest investigators in basic and applied studies of the diaspidid parasitoids as key regulating factors in biocontrol. After a general introduction to the importance of diaspidids species and their parasitoids, the book contains the different components of the population ecology, host-host stage preference, reproductive strategy, searching for a host, pupal cold storage, mass production and release experiments of parasitoids.