Forewing length of 16-20 mm. Forewings olive-grey with pale greenish and white markings. One of these markings is a silvery white kidney shaped spot and the medial line is grey. Hindwings are pale grey with a slight yellowish sheen and a dark grey marginal band. The head is dark grey brown and the anterior thorax bears a weak dark tuft.
Newly hatched larvae are ca. 3 mm long, pale green with a pale yellowish stripe along each side. Final instars reach 40 mm long and are variable in colour with green, brown or velvety black forms. A yellowish orange stripe is present along each side and the head is pale brown. The black form has 3 broken white lines along its back.
Sculptured and ribbed, initially white and becoming darker with age. Laid in clusters of 50-500 eggs on the lower surface of leaves. Eggs hatch within a week.
A range of agricultural crops including cabbage, oilseed rape, Lucerne, tobacco and pea.
Young larvae feed on the underside of leaves, chewing irregularly sized holes. Mature larvae feed more voraciously and will feed on seed pods or developing flowers and bolls.
3-4 (climate dependent)