Eggs are ovoid and candid white. Larva is greenish yellow changing to pure yellow by the third day. From the third instar the body color changes from yellow to cream, green, blue, or white. The larvae are either spotted or unspotted. A white powdery substance covers fully mature larvae. The cocoon is distinguished from other species by its elongated, soft wooly, white, and peduncleless characteristics. Furthermore, the cocoons do not produce a continuous thread. Male moths reach a length of 2.3 cm and females reach 3 cm. Average wingspan is 13-15 cm respectively for male and female S. cynthia moths. This species may produce up to 5-6 generations per year when domesticated whereas the wild relatives have 1-3 generations per year. S. cynthia larvae feed primarily on the castor plant (Ricinus communis L.), which can also be utilized to make castor oil, and kesseru (Heteropanax fragrans Seem.)