Wingspan of 35-45 mm in males and 45-55 mm in females. Forewings are typically white (dark forms also exist) with dark spots and transverse wavy lines. Hindwings are grey-brown with small dark or light patches at edges. Patches of pink or red often present on the abdomen of females, with black bands.
First instar larvae are ca. 4 mm in length, hairy and initially tan coloured, becoming black. Final instars reach 30-40 mm in length with a tannish, greenish or dark-greyish
body with extensive brown or black mottling. A brown to black mid dorsal stripe is present. Head is orange-brown with brown and black spots.
Spherical, ca. 1mm in diameter and often flattened on lower surface. Initially orange-brown, becoming brown with age. Laid in small clumps covered with hair from the
female’s abdomen in bark crevices or under lichen.
Predominantly coniferous trees, in particular Norway spruce (Picea abies) and Scots pine (Pinus sylvestris), but will also attack deciduous trees.
Newly hatched larvae usually move to the crown to feed on younger soft needles and may also feed on buds and male cones. Larval feeding results in piles of frass and damaged needles at the bottom of trees. In deciduous trees larvae feed on young leaves, consuming the entire leaf except the veins.
