Wingspan male 15–20 mm, female 17–22 mm. Readily recognised by its long, porrect labial palpi.
The male is variable but is generally yellowish to greyish/brown with brown markings. The most noticeable being a diagonal band from the costa to the dorsum.
The female is generally a uniform reddish/brown.

Eggs are flat, oval, initially apple green, later becoming citreous and finally orange-yellow.

Length of mature larva is 18-30 mm, greenish-grey or dirty-green, lighter beneath, with head and pro-thorax dark brown.

The pupa is dark brown with a long cremaster containing two lateral and two terminal bristles.

Eggs are laid in batches containing 40–100 eggs covered by a gland secretion hardening in the air.
Larvae hatch after 10 days and enter diapause almost immediately, hiding in bark crevices. They resume their activity only when the first leaves appear next spring, migrating to the top of the branches and feeding on buds initially and on leaves later. They exhibit typical territorial behaviour, marking and defending their territories with knocking sounds.
Pupation takes place in a shelter between spun leaves or a rolled leaf.

The larva is highly polyphagous on a high number of trees, shrubs and herbaceous plants and causes occasional but serious damage to grapevines, strawberries and other fruits.