Coleoptera comprise the greatest number of described species (ca. 300,000) of any order, and occur in all habitats except the depths of salty seas. Crowson (1981) reviewed the morphology and biology of Coleoptera including a chapter on predaceous beetles. Balduf (1935) extensively covered the literature on the biologies of entomophagous Coleoptera up to 1933. Keys to larvae of families and many subfamilies of the order have been written by Klausnitzer (1978) and Lawrence (1991a), but little is known about the ecological importance of the many species that live in soil and in water. Even the prey spectra of many predaceous families are poorly known. However, some of the most spectacular successes in classical biological control have involved the introduction and establishment of predaceous Coleoptera, and the roles that various endemic entomophagous Coleoptera play in the natural biological control of their prey are slowly being revealed.