Ground Beetles
Created | Updated Jul 2, 2005
Ground beetles (family Carabidae, order Coleoptera) are generally pictured as large insects, about 10-20mm long, scurrying about across the ground and hiding under logs and stones. Generally though adults range between 4-30mm. They are one of the most abundent and diverse beetle families with over 20,000 species. Ground beetles or carabids were once described as two families, the ground beetles and the tiger beetles, but since have been described as belonging to the same order. Ground beetles are mostly nocturnal and dull coloured, and tiger beetles are diurnal and more colourful. Depite there not being much to distinguish ground beetles from any other beetles, most people have no trouble identifying them despite not knowing what the differences are.
Is it a ground beetle?
All ground beetles have the following features.
- Threadlike antennae with short fine hairs near the tip
- The hind tarsi (leg) is neither broad nor fringed
- Each tarsi has five segments
- The hind coxa (the upper leg segment or hip) extends backwards so only the sides of the first abdominal segment can be seen
What Ground Beetles Eat
Almost all ground beetles adults are carniverours and eat all sorts of prey including slugs, snails, caterpillas, weevils, leaf beetles and all sorts of other plant pests. They are therefore very useful in gardens to keep down pest numbers. A few ground beetles though eat plants either as part or all of their diet, and some are considered pests such as the strawberry seed beetle. The larvae are also mostly carniverous though some scavange on dead insects and others on plants, especially plant seeds.
Some ground beetles are highly specialised in their diet, feeding on specific prey such as seeds or aphids. These tend to have large mouthparts specific to their chosen prey. Others have smaller, morre general mouthparts and feed on a huge range of prey. Ground beetles are active beetles and so good at catching and eating other invertibrates.
Getting About
There are two ways of getting about for ground beetles; on foot or flight. Tiger beetles quite often fly in search of their food. Not all ground beetles though can fly, as many have become too adapted to life of scurrying about on the ground. Others can absorb their hind wings if food reserves are low, and so have to rely on their legs in order to disperse. Ground beetles are capable of travelling huge distances, and can move quite fast if they want to. One very common ground beetle, Nebria brevcollis, has been found to travel an average of 20m every night.
Changes in Land Use and Beetle Extinctions
Ground beetles have been shown to particularly responsive to changes in land use, especially to the large amounts of intensive agricultural land in most developed countries. Many ground beetles have become adapted to particular habitats or food sources, so as their range decreases they find themselves unable to compete with the more general species. As a result, many ground beetles are becoming extinct, especially in western European countries and Japan.
