Not all insects are pests. There are some that are beneficial by eating other small garden creatures, some of which may be pests.
A typical ground beetle is the large ‘black-clock’ beetles, 10-20 mm long, often seen scampering across the ground or hiding under stones and logs in the garden,. Nearly all are extremely beneficial and help control garden pests . . . . . .
The Carabidae, or ground beetles, are one of the largest and best known families of beetles (Coleoptera), with over 20,000 different species worldwide – about 340 of these occur in Britain. Most species are nocturnal and sombrely coloured black or brown, but a few display iridescent and metallic blue, bronze, green or reddish reflections, and the family also includes the brightly coloured, and mainly diurnal, tiger beetles.
A typical black ground beetle (Pterostichus melanarius) found commonly in gardens and farmland where it preys on aphids, caterpillars, wireworms, slugs and other pests
Carabid beetles and their larvae are mostly carnivorous, although some probably also scavenge on the dead remains of insects and other invertebrates, whilst others feed extensively on vegetable matter, especially plant seeds. A few of the carnivores are specialized caterpillar or snail hunters, or prey on a fairly narrow range of small insects such as aphids, springtails and mites; but most species are not very fastidious and a mixed diet of many different invertebrates, and ground beetles are extremely beneficial and important predators which help in the natural control of many garden and crop pests, such as grasshoppers, crickets, termites, aphids, plant bugs, leaf beetles, weevils, wireworms, chafer grubs, butterfly and moth caterpillars, sawfly caterpillars, crane flies (leatherjackets), fruit flies, gall midges, many other fly pests, as well as slugs and snails. Ground beetles lay eggs in the soil or in accumulations of organic matter.
The larvae are elongate, relatively soft-bodied grubs that have three pairs of legs near the head end.
The head, thorax and usually some of the abdominal segments are brown or black but the underside is creamy white.
The larvae remain in the soil or leaf litter, where they feed on small invertebrate animal and their eggs.
Please do not kill these when you find them in your garden, garage shed etc. They may look bad but are your friends and are a free form of pest control (or The Good Guys)