Information on the diversity and roles of two groups of arthropod predators (Neuroptera and Araneae) in Australian cropping systems is reviewed, as a foundation for discussing the properties of such predators that may render them useful bioindicators, and for discussing their ecological roles in agroecosystems. Predators are a prime target for conservation and augmentation, reflecting their perceived or actual positive roles in pest management, but most appear to have little value as true bioindicators in agricultural environments. In Australia, Neuroptera are represented by very few species in most agroecosystems, and all of these species are polyphagous generalists. Biological knowledge of Araneae, and of the factors that influence their species richness, is too scanty to enable sound understanding of changes in assemblage composition that might otherwise be regarded as ‘indication’. The current value of these groups as bioindicators is minimal.