Both chafer grubs (the larvae of chafer beetles) and leatherjackets (the larvae of crane flies, or daddy-long-legs) live in the soil. They eat the roots of grasses and, as a result, cause problems in lawns.
Leatherjackets
Leatherjackets have tubular, greyish-brown or darker bodies, up to 3cm (1¼in) long, with no legs or an obvious head. They may be confused with cutworms [LINK to Caterpillars], the caterpillars of several moth species.
Adult crane flies mainly emerge and lay their eggs in the turf or soil surface from August to October. When the eggs hatch in a few weeks, the young leatherjackets start eating plant roots. During mild winters, they continue to feed and can cause lawn problems by late winter. During cold winters, they overwinter as small larvae and don’t cause significant damage until the following summer. When fully grown, the leatherjackets pupate in the soil, eventually emerging as new adults crane flies.
Leatherjackets and leatherjacket damage are usually worse in a wet autumn.
Chafer grubs
Chafer grubs are large, creamy-white, C-shaped grubs with large brown heads and six legs. They can be confused with vine weevil larvae, but these are much smaller and legless.
The most damaging chafer species are the garden chafer, Phyllopertha horticola, and the welsh chafer, Hoplia philanthus – which isn’t just confined to Wales. Adult garden chafer beetles are around 9-10mm (3/8in) long, with a metallic green head and body with light brown wing cases. Adult welsh chafer beetles are the same size with a black head and body and reddish-brown wing cases.
In late spring/early summer, usually at dusk, the adult beetles fly up from the lawn in large numbers to mate. Females lay eggs in the turf and these hatch into the larvae (grubs), which start to feed on the grass roots. At first, they do little significant damage, until autumn, as they become fully grown. They overwinter in the soil as larvae and pupate in the soil in spring.