The natural enemies of insects

All insects and mites have natural enemies. Some pests have more— or more efficient—natural enemies than others. Biological control relies on effective natural enemies that can be managed by humans.

Types of natural enemies

Vertebrate natural enemies of insects include certain birds, such as flycatchers, woodpeckers, purple martins, starlings, and chickens; certain mammals, such as bats, moles, voles, skunks, and hogs; and toads, frogs, and lizards.With a few minor exceptions, these cannot be managed to reduce the populations of pests significantly, and they will not be considered further in this publication.

Insects and mites that feed on other insects or mites make up the most important group of natural enemies. This is an extremely large and diverse group. Unfortunately, because beneficial insects are often tiny and nondescript, they are frequently overlooked by even the most dedicated practitioners of biological control. Only the large, common, or brightly colored species, such as praying mantids and lady beetles, are commonly recognized.

Insects that eat other insects are either predatory or parasitic. Predatory insects, or predators,are usually much larger than their prey.They eat and kill many prey as they grow and reproduce. Many predators will feed on almost anything they can catch, but some specialize in consuming certain prey types. Most predators are fairly mobile and can search rapidly for prey.The adults of relatively nonmobile species, such as hover fly larvae, lay their eggs in the immediate vicinity of prey insects, such as aphids. Some types of predators undergo simple metamorphosis—the various families of predatory bugs are examples—whereas others undergo complete metamorphosis—examples include the lady beetles and lacewings (see table 1).Many important predators are predatory as both immatures and adults.

Table 3. Major groups (orders) of insects, listed in order of increasing evolutionary complexity.1
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