Only a small percentage of these species are pests, but people are often the most familiar with these because they damage crops or injure humans or their livestock. However, there are many more insects that are considered beneficial because they feed on the pest insects. If there was nothing to prevent plant-feeding insects from surviving and reproducing, they would increase in numbers, and eat up every host plant until there was no longer anything left to eat. Obviously that doesn't happen, since there are lots of plants around us. The populations of all insects, including pests, are regulated by a variety of natural environmental factors, including weather and other organisms.
Natural enemies are organisms that kill individuals of another species.
Beneficial insects are either predators or parasites. Common predators include lady beetles and green lacewings that feed on aphids, and spined soldier bugs and ground beetles that feed on soft-bodied insects, such as caterpillars. As a winged adult it searches for more hosts for its offspring. Common parasites include tachinid flies and various stingless wasps, often developing in caterpillars. These insects are usually more choosy about their host than predators are about their prey, often selecting only one species of insect to parasitize.