[1][2] They range in size from 12 to 35 mm (0.47 to 1.38 in)[1][2] and are blackish or reddish-brown in colour, without prominent markings, and often rather hairy ventrally.

However, white grubs (reaching 40–45 mm long when full grown) live in the soil and feed on plant roots, especially those of grasses and cereals, and are occasional pests in pastures, nurseries, gardens, and golf courses.

[3] The grubs sometimes attack vegetables and other garden plants, e.g. lettuce, raspberries, strawberries, potatoes, and young ornamental trees.

Injury to the roots and rootstock causes small saplings and tender tap-rooted plants like lettuce to wilt suddenly or to show stunted growth and a tendency to shed leaves prematurely.

The egg hatches and the fly larva enters the body cavity of the beetle, feeding on and eventually killing the host before pupating.

[4] Wasps in numerous families, including Pelecinidae, Scoliidae, and Tiphiidae, are parasitoids of Phyllophaga grubs.