Landscape - Some Beneficial Beetles

Everyone is aware that lady beetles are beneficial as they are a great aphid predator. However, there are other beneficial beetles in the landscape. The following is an article on the subject.

Ground beetles (family Carabidae) are important predators that can be found in most gardens and home grounds. They may be the most numerous predatory insect around the home. They vary in size from less than ¼" to over 1½" long. Adult ground beetles run quickly when disturbed, but they rarely fly.

The adults of most ground beetles are dark brown or black, shiny, and somewhat flattened, with slender legs for running. A few are iridescent blue or green. They are commonly found under leaves or debris, in cracks in the soil, or running along the ground (but not often in bright sunlight). Some species also climb into trees, shrubs, and crop plants looking for prey. They may wander indoors at ground-level entry areas.

Adult ground beetles are fierce predators that chew up their prey with large, sharp mouthparts. Common prey include caterpillars, grubs and adults of other beetles, fly maggots and pupae, earthworms, and other small soil dwellers. They can consume their body weight in food daily.

Firefly larvae feed primarily on snails and slugs. Like the more familiar adults, they are mainly nocturnal in habit. They prefer moist habitats, such as under boards, decaying vegetation and beneath bark. Closely related glowworms (larvae and the adult female are luminescent) occur in more wooded areas and feed primarily on millipedes and soft-bodied insects under decaying tree bark.

Soldier beetles resemble fireflies – their larvae are predacious (as are fireflies), but compared to fireflies, adults and larvae are more active during the day. Acommonly are seen on flowers, and larvae prefer the "old field" habitat. Click beetles are another familiar adult beetle. The larvae of some click beetle speciefeed on insects in dark, secluded environments.

The family Staphylinidae, or rove beetles, with about 2,900 species, is the largest family of North American beetles. Most species are small and seldom seen. Although common, the group as a whole is not well studied. Some species are predaceous as in adults and larval stages; the larvae of other species are parasitoids and others are scavengers.

Adult rove beetles are generally less than ¾ inch long. They are recognized by their slender, usually black or brown bodies and shortened front wings (elytra) that may look like pads on the abdomen. When disturbed rove beetle adults have the distinctive behavior of curling the tip of the abdomen upwards. Adults are usually strong fliers despite the shortened forewings (hindwings are normal sized). The mobile larvae of nonparasitic rove beetles may be distinctly segmented.

Most rove beetles are found in association with soil or decaying organic matter. They may be seen under debris or rocks, in compost piles or crawling on plants. They are frequently found in soils when in home gardens. Adults will visit flowers to feed on pollen.

Predaceous rove beetles, depending on the species, feed on eggs and larvae of mites, insect eggs or small soil insects. Some feed on the eggs and maggots of flies. A few species found in vegetation feed on many types of small insects and mites.

Information from Dewey Caron, Extension Entomologist, UD.