The chafer species most often found damaging lawns are the garden chafer, Phyllopertha horticola, and the welsh chafer, Hoplia philanthus; the latter is often found in sandy soils and is not confined to Wales. Adults of P. horticola are about 9mm (3/8in) long and have a metallic green head and thorax with light brown wing cases. Hoplia philanthus is a similar size with a black head and thorax and reddish brown wing cases.
Adult chafer beetles feed on the foliage of many plants but are generally not a problem. They will, however, sometimes damage the flowers of roses and other plants. In heavily infested gardens, the adult beetles fly up from turf in large numbers at dusk from late May to June. Eggs are laid in the turf and these hatch a few weeks later. The grubs feed on roots but do not cause significant damage until early autumn, by which time the larvae are becoming fully grown. They overwinter as larvae and pupate in the soil in the spring.
Two other species, which are generally less damaging, are the summer chafer (Amphimallon solstitialis) and the brown chafer (Serica brunnea). The latter is generally found in or near wooded areas on sandy soils and is about 9mm long and reddish brown in colour. The summer chafer is light brown, about 16mm long, and distinctly hairy.
One species of chafer grub is often found in compost heaps, the larvae of the rose chafer (Cetonia aurata). This is a species that feeds on decomposing organic matter and as such is a useful garden insect. The adult beetles are about 2 cm (1 inch) long and metallic green.
Chafer grubs can appear similar to the larva of the stag beetle (Lucanus cervus). However, larvae of the stag beetle are always associated with dead wood, usually tree roots and can reach 11 cm long (nearly 4 inches). Stag beetles are uncommon and cause no damage in gardens and should be welcomed.