The two sexes are easy to distinguish: the females have white wings with black spots and thin antennae, while the males are darker and smaller and have feathery antennae. The wings are marked with wavy grey lines in both sexes. Their wingspan is 3 to 4 cm for males and 5.6 to 6.7 cm for females. The females are so heavy that they cannot fly.
In their last stage, the caterpillars are hairy and have small raised coloured spots on their backs. The spots nearest the head are blue, and those farther down the body, red. The head is black and yellow. The caterpillars may be up to 6.5 cm long.