Eggs are small (1 mm in diameter) and bright yellow when new, but turn black with age. Larvae generally develop through six instars. First-instar larvae are light brown or orange, while third instars and later are banded orange and black; the dark bands become more pronounced with age. Larvae are capable of sequestering alkaloids from their host for use as toxic defenses against birds and other animals. The conspicuous colors of cinnabar moth larvae serve as warnings to those potential predators. Mature larvae are up to 25 mm long. Pupae are a dark maroonish-brown. Adults have black forewings with two red dots and red-lined borders, and hindwings are bright red. Wingspans may be up to 4 cm, and coloring often fades as moths age.