Two soil-dwelling beetle families are primarily gardener’s friends: ground beetles (carabids) and rove beetles (staphylinids). Adults and larvae of most species eat insects, slugs and other invertebrate animals.
Rove beetles have elongate bodies with short wing-cases that leave most of the abdomen uncovered. They are 2-30mm long and generally black or brown in colour.
Devil’s coach horse (Staphylinus olens) is one of the larger rove beetles and is often found under logs or pots.
A smaller species, Atheta coriaria, is bred and supplied as a biological control for fungus gnat larvae in glasshouses.
Ground beetles are 2-25mm long and mostly black but some are brown or green. Most feed at ground level, but some will climb plants to feed on aphids and small caterpillars. One common garden species, the violet ground beetle (Carabus violaceus), has metallic-purple edges to the wing-cases and thorax. Being one of the bigger carabids, it will feed on larger garden pests, such as slugs, leatherjackets and cutworms.
Shiny black Poecilus cupreus is one of many black predatory ground beetles that live in gardens. Its long legs and powerful jaws mark it out as an active predator.