The male promethea is usually black although males sometime show a reddish hue. I once heard a woman tell my father that he had the sexiest backyard in New Jersey. She was responding to his explanation of the swarms of male promethea flying around a backyard cage holding a scenting female. This species mates readily, even in small cages. The pair usually remains coupled until the following evening.
Incubation is eight to twelve days.
The caterpillars are striped around the girth and are gregarious for the first two instars. The coloration changes dramatically for the last three instars with the body losing its stripes and developing bright red or orange thoracic tubercles and a yellow caudal tubercle. Photo courtesy Univ. The pupa is a dark brown and almost completely fills the tightly woven inner cocoon. Wild promethea cocoons are often found hanging from hostplants after leaf drop as the larvae always spin a strong peduncle that allows the long, slender cocoon to hang from the tree like a Christmas ornament.