Adults are 10–15 mm long with variable coloring. Typical adults have white or yellowish wings with small gray to brown mottling, sometimes appearing as stripes on wing veins. Their wingspan is 16–22 mm. Overwintering adults emerge during early spring to lay eggs on stems and leaf axils of common gorse, Scotch broom, and Portuguese broom. Eggs are yellowish, cylindrical, and 1 mm long. Larvae hatch in late spring. Using plant material and webbing, larvae form tubes on shoot tips of their host plant. Larvae vary in color from yellowish-gray to brown and can be up to 15 mm long. They develop through five instars, feeding on young leaves, shoot tips, and flower buds. The brown pupae are 10–15 mm long. Pupation occurs within the feeding tubes. New adults emerge in late summer and overwinter in their host plant foliage. There is one generation per year.