Callosamia promethea, commonly known as the Promethea Silkmoth, is a remarkable member of the Saturniidae family, native to North America. This species is especially admired for its striking appearance and the pronounced differences between males and females, a phenomenon known as sexual dimorphism. Adult moths have a wingspan of approximately 7.5–10 cm, making them quite large and eye-catching. Males are predominantly dark brown to black, with wavy white markings on their wings, creating a bold and dramatic look. In contrast, females are reddish-brown with similar patterns but a lighter overall tone, lending them a more muted elegance.
The caterpillars of the Promethea Silkmoth are just as fascinating. They are large, bright green, and adorned with yellow tubercles along their bodies. Near the head, they have a pair of distinctive red-tipped "horns," which can serve as a deterrent to predators. These caterpillars feed on a variety of host plants, including wild cherry, sassafras, sweetgum, and tulip tree, and play an important role in forest ecosystems. Tulip Tree is increasingly grown as an ornamental in the UK, and it is worthwhile using for rearing larvae if you can find some growing locally, as this is their most commonly used host plant in the USA and provides excellent results. The silken cocoons they produce prior to the pupal stage are well-camouflaged and secured to twigs, helping the moths survive harsh winters before emerging in spring.
Promethea Silkmoths inhabit deciduous forests, woodlands, and areas with an abundance of their host plants. They are found across the eastern United States and southeastern Canada. Adults are nocturnal and do not feed, relying on energy stored during their larval stage to sustain them through their brief adult lives. The males are diurnal, and strong and fast fliers, flying during the late morning until mid afternoon to locate females, who emit pheromones to attract mates. Females are more sedentary, remaining near their emergence sites until they have mated, after which they fly at night to deposit their eggs, though still generally remaining in one area.
Difficulty - Cocoons are easy (1/10); caterpillars can be challenging (5/10)
Host plants - Cherry; Birch; Willow; Tulip Tree; Ash; Sweet Gum; Magnolia; & multiple others
Conditions - Room temperature
Lifecycle - Two broods annually with the second overwintering as cocoons
