Ground Beetles: our allies against garden pests
Make ground beetles welcome in your garden
Ground beetles are allies in our battle against pests. Around the world there are some 25,000 species of these beetles, and most of them, both larvae and adults, are predators of a wide variety of insects.
Many also attack slugs, snails and earthworms.
Appearance of ground beetles
Ground beetles (Order: Coleoptera; Family: Carabidae) often have grooved wing cases and a metallic green, blue or brown colour, but many also are dull brown or black. They are most active during the night, but can also be seen during the day, running at high speed through vegetation or up and down trees. Although some species can fly, they seldom do. In most species the wings have totally disappeared and the wing cases have grown together to form one strong shield.
This is a big-headed ground beetle, Scarites subterraneus
Biology of the ground beetle
Ground beetles deposit single eggs on or in the ground; some dig a small hollow in the ground with the tip of the abdomen into which they lay an egg. A few species use their mandibles to construct mud cells on leaves or low plants.
The females of at least one species (Pterostichus anthracites) guard their eggs until they hatch (see this abstract of the Entomological Review 88 number 8 (2008), 904-909). The larvae are strongly built and have chitinous plates covering their backs. They are fierce predators which hide during day time in self-dug 'corridors' in the ground, from which they emerge at night to hunt. Pupation occurs also in the soil.
Adults eat a wide range of insects, as well as snails, slugs and earthworms, which they grab and chew with their strong mouth parts. Irresistible is also over-ripe fruit. The adults overwinter in cracks and crannies and reappear in early spring. They usually die well before the next autumn.
Some books of interest
Video showing how ground beetles attack and eat their prey
Natural enemies
Just as all insects, ground beetles have their own natural enemies, and are attacked by birds, toads, ants and spiders.
How to lure ground beetles into your garden
- To protect ground beetles against being attacked, provide them with enough cover: do not remove dead leaves from the soil in late summer and autumn. This not only keeps them out of sight of birds and toads, but also maintains a moist environment which they prefer.
- Alternatively, provide hiding places in the form of rocks, thick organic mulches or overturned flower pots (with uneven rims or placed on uneven ground) designed, for example, as garden borders. One could put a few pieces of over-ripe fruit near or in these hiding places to lure ground beetles to the garden.
Links to interesting sites on ground beetles
- Ground Beetles - Habits and Traits of Ground Beetles, Family Carabidae
Ground beetles hide under rocks and boards by day, and hunt insects and other invertebrates by night. Most are predatory in both the larval and adult stages, making ground beetles true powerhouses among the beneficial insects of the garden. - Entomological Review
The sex and age structure of the population, developmental biology, and parental care were studied in Pterostichus anthracinus from the floodland plain of the Desna River.
