As a means of insect pest management, classical biological control shares the advantages of other biological control methods in that (1) no harmful chemical residues are introduced in the environment; (2) the insect pest cannot develop resist ance to the beneficial species because the natural enemy adapts as the pest changes; (3) once a biological control agent becomes established, the control of the pest is usually permanent; and (4) a small initial investment in biological control usually results in" a large return in the safe, permanent management of an insect pest.