biological control

The amount of food for each species of course gives the extreme limit to which each can increase, but very frequently it is not the obtaining of food, but the serving as prey to other animals, which determines the average number of a species.
Darwin on the Origin of Species (1859)

Biological control when considered from the ecological viewpoint as a phase of natural control can be defined as the action of parasites, predators or pathogens in maintaining another organism's population density at a lower average than would occur in their absence
P. DeBach (1964, p. 6)