More beetle species have been described than any other order of animals. Some beetles are well-known such as ladybirds and the stag beetle others may be less familiar, such as the devil’s coach horse.
Beetles can be distinguished from other insects by their hardened forewings (elytra), which provide protection for the hind wings and abdomen. In many beetles the hind-wings are used to fly. In addition, beetles have biting mouthparts, which differentiate them from other insects that might appear superficially similar, such as the shield bugs (Hemiptera), which have sucking mouthparts. Some beetles, including rove beetles, have shortened elytra that cover only part of the abdomen.
Beetles go through complete metamorphosis; the larval stage of beetles is different in appearance and, often, habits, to the adult. In some cases the larva is the only stage that feeds and in some wood-boring insects can last several years, whilst the adult stage may live for only a few weeks or days (e.g. the stag beetle).
British beetles range from under 1mm in length (the featherwing beetles) to 6cm in length (the stag beetle)
Everywhere except the sea and polar ice caps.
Over 350 000 species described worldwide. More than 4000 species occur in the UK.
Where to find them in the garden
Everywhere! Some beetles can be found feeding on nectar and pollen, including the small (< 3 mm) metallic pollen beetles (Meligethes spp.) and soldier beetles. Ponds harbour beetles belonging to the family Dytiscidae, including the 3cm long great diving beetle (Dytiscus marginalis). The water surface is often disturbed by the erratic movements of whirligig beetles. Leaf beetles and the weevils are herbivores and some can damage garden plants. You can discover may ground-dwelling beetles under rocks, in leaf litter and the compost heap, including predatory ground beetles (Carabid family) and rove beetles. In some gardens the dim light of the glow worm (Lampyris noctiluca) can be glimpsed on summer nights. Many species of beetle are associated with dead and dying wood and fungi. The peeling bark of dead trees and chopped logs is often marked with the characteristic tunnels of the bark beetles. The stag beetle feeds as larvae on the rotting roots and stumps of felled or dead trees.
Role in the garden
Beetles are invaluable! While some beetles can kill or damage plants, others keep pest numbers in check. Many ladybirds are voracious predators of greenfly and other aphids. Ground beetles and rove beetles help reduce vine weevil and slug numbers. Other beetles feed on and help recycle decaying organic matter. For example fleshy white grubs of the rose chafer (Cetonia aurata) may be found at the bottom of compost heaps, while dung beetle larvae dispose of excrement.