The subject area embraced by the term "biological control" in its classical sense is very broad indeed. The term itself was apparently first used in 1919 by the late Harry S. Smith, and was then used specifically in reference to the suppression of insect populations by the actions of their indigenous or introduced natural enemies. The California school of biological control specialists who followed in Smith's footsteps have traditionally differentiated "natural" biological control (by indigenous natural enemies) and "applied" biological control (by man-introduced natural enemies). Subsequently, the philosophy broadened beyond the original narrow concern with population suppression of insects (and especially pest insects), to embrace directed activities