Strictly speaking, insectivores are any predators that catch and eat insects. Often, however, insectivorous predators also eat other small invertebrates, such as spiders, millipedes, centipedes, and earthworms.
Some insectivores specialize in catching and feeding upon flying insects, sometimes called aeroplankton. Some prominent examples of this insectivorous feeding strategy include dragonflies, smaller species of bats, flycatchers, swallows, and swifts. Insectivores that feed on flying insects must be quick and maneuverable fliers, and they must have acute means of detecting their prey. Most species are visual predators, meaning they detect flying insects by sight. Bats, however, feed in darkness at night or dusk, and they locate their prey using echolocation, a type of biological sonar.
Other insectivores are gleaners, and they carefully search surfaces for insects to eat. Most gleaners visually examine the surfaces of plant leaves and the branches and trunks of trees. Many birds that exploit the forest canopy hunt insects in this way, for example, warblers and vireos; as does the praying mantis.
A few species of insectivores specialize by finding their prey inside of wood. These insectivores may excavate substantial cavities as they search for food, as is the case of many species of woodpeckers, and sometimes bears searching for beetle grubs or carpenter ants.
Large numbers of insects live in soil and in the organic matter that sits atop the soil. Many species of burrowing and digging small mammals feed on insects and other invertebrates in this substrate, including shrews, moles, and hedgehogs (in fact, the order of these small mammals is called Insectivora). Some birds also hunt insects
located in surface litter, for example, thrushes and grouse. There are also many species of burrowing, predacious insects and mites that hunt insects within this zone.
Freshwater lakes, ponds, and wetlands can harbor enormous numbers of insects, and these are eaten by a wide range of insectivores. Trout, for example, feed voraciously on aquatic insects whenever they are available in abundance. A few species of birds, known as dippers, actually submerge themselves and walk underwater in mountain streams, deliberately searching on and under stones and debris for their prey of bottom-dwelling insects.
Virtually all insectivores are animals. However, a few plants have also evolved specialized morphologies and behaviors for trapping, killing, and digesting insects and other small invertebrates, and then absorbing some of their nutrients. Usually, these plants grow in nutrient-deficient habitats, such as bogs and dilute lakes. Examples of so-called insectivorous plants include the Venus' flytrap, sundews, and pitcher plants.