The author reviews the complex of interrelationships embracing plant-arthropod and higher-level, arthropod-arthropod interactions, as related to natural control phenomena. Included are not only biotic control agents which determine paths and extent of energy flow, but also the evolutionary implications of how this has come to be. Examples of the way in which predaceous (or parasitic) arthropods of primary, secondary, and tertiary order may influence the competitive status of plants, and thus the composition of respective species in vegetation, are considered. We also consider: development by plants of their own resistance to phytophagous arthropods; counterselection among specialized phytophagous species in order to stay in the game; and circumvention of the biological control action of natural enemies of specialized phytophagous species, thus relieving the continuing selective pressure on the plant to offset the plant's countermeasures.The author concluded that plant resistance to phytophagous arthropods, and the interplay of these relationships, the interplay among the plant hosts and their phytophagous predators (including parasites), and among the latter and their own carnivorous predators (including parasites), and at higher levels as well, have had striking influences in the evolution of species, and in their functional, dynamic roles in explaining the population dynamics and energetics of complex communities.