Callosamia promethea, the Cherry silkmoth or Promethea silkmoth, is an iconic species of silkmoth found in the eastern half of the United States, up to Canada. The species is highly dimorphic; males are black, while females are rusty orange. Most populations of this species only produce a single generation a year, although in the most southern part of its range, the species is capable of producing a partial second generation. Interestingly, this species, unlike a lot of other silkmoths, is diurnal/crepuscular – males fly in broad daylight, and are active from 16.00 to 19.00 in most locations (from afternoon to dusk).

This species is highly polyphagous, and caterpillars seem to be able to feed from a large selection of trees and shrubs. In particular, their favorites in the wild appear to be sweetgum (Liquidambar sp.), spicebush (Lindera benzoin), sassafras (Sassafras albidum), tulip tree (Liriodendron tulipifera), sweetbay (Magnolia virginiana), white ash (Fraxinus americana), lilac (Syringa vulgaris), wild black cherry (Prunus serotina), red maple (Acer rubrum) and beaked hazelnut (Cornus cornuta).

In the U.S.A, the species is sometimes raised people in captivity, since the species can be common in forested areas or suburbs that have some intact vegetation – and both the caterpillars and moths are very charismatic. While the species is not very difficult to breed, it is recommended to have some basic experience with moths – since the caterpillars can be a little sensitive to diseases and infections, especially when raised in large numbers indoors.

• Difficulty rating: Moderate (the good news is that the moths are very easy to pair, and thankfully caterpillars accept many types of food – but the bad news is, larvae are very sensitive to infections)
• Rearing difficulty: 7/10 (From egg to pupa)
• Pairing difficulty: 5/10 (Archieving copulations)
• Host plants: Sweetgum (Liquidambar sp.), spicebush (Lindera benzoin), sassafras (Sassafras albidum), tulip tree (Liriodendron tulipifera), sweetbay (Magnolia virginiana), white ash (Fraxinus americana), lilac (Syringa vulgaris), wild black cherry (Prunus serotina), red maple (Acer rubrum) and beaked hazelnut (Cornus cornuta), Betula papyrifera (paper birch), Salix sp. (Willow), Juglans sp. (Walnut), Ligustrum sp. (Privet), Populus sp. (Poplar tree), Tilia sp. (Lime tree), Laurus nobilis (Laurel), Cinnamomum camphora (Camphor), Pyrus communis (Pear), Rosa sp. (wild rose), Hickory (Carya), Malus (apple) and most likely many more! It is a great idea to experiment with various Rosaceae, Salicaceae, Juglandaceae, Oleaceae, Tiliaceae and Lauraceae.
• Natural range:  Eastern half of the United States; Canada
• Polyphagous: yes
• Generations: Mostly univoltine (single brooded); but southern populations may have a partial second generations.
• Family: Saturniidae (silkmoths)
• Pupation: Cocoon (silk encasing)
• Prefered climate: Temperate climate; warm and dry summer, cold winter
• Special notes: The males need sunlight to pair. This is a diurnal (day flying) species of silkmoth.
• Estimated wingspan: 65mm-100mm (medium sized silkmoth)
• Binomial name: Callosamia promethea (Drury, 1773)

The eggs of Callosamia promethea can be incubated in petri dishes. From this moment and beyond, in 10 to 15 days time many tiny, striped caterpillars will crawl out. These can be transferred to a plastic box with leaves. And now the fun begins!

The first instars of this species are social; and they will feed in groups. At this point, it is recommended to keep many of them together in the same container – social species tend to grow better in captivity if given many friends! Their group behaviour encourages other caterpillars to start eating.

Once they shed their skins, they change. Instead of being black and yellow, they become pale and white, with double black bands, and yellow tubercules. At this point, the larvae are still social, and like to feed in groups. The first and second instar can be raised in a plastic box and tend to be the easiest instars to grow. After this, it gets a little more challenging.

Instar number three is when they get really beautiful. Pale white with black tubercules; except for their huge yellow thorarical tubercules, and one large anal tubercule. Very adorable! Generally speaking, L1 and L2 are rather easy – it’s L3, L4 and L5 where breeders can experience troubles. From instar 3 to instar 5, it’s important to keep the caterpillars warm, dry and ventilated. This can be done by rearing them outdoors in during a warm summer (but don’t expose larvae to full sunlight), or indoors in a pop-up cage, preferably in front of an open window with airflow. The caterpillars do not appreciate being being wet or too humid for extended periods of time. Try to avoid spraying this species with water; if you give the caterpillars fresh leaf, they will recieve all the moisture they need from their food.

Important to remember that in L3, the caterpillars are still social. They often still hang out in groups, and feed together from the same leaves. Although they prefer to form smaller groups, often consisting of 3 to 10 individuals. There is no need to seperate them yet.

Instar number 4 reminds me of a big version of instar number 3; but there is one easy way to recognise them. In instar number 4, their tubercules turn orange over time instead of yellow!

The most impressive change however, happens in the final instar. Their tubercules become a deep, bright, vibrant red colour. And their black ‘warts’ are surrounded with almost bright blue, neon fluorescent rings, on top of their adorable yellow terminal tubercule.

Important to remember is that the final instar is solitary! Callosamia promethea is a little bit of a paradox, because they young larvae prefer to be in groups; but the opposite is true of the fully grown caterpillars. The fully grown caterpillars do not like being overcrowded. They should be given space, warmth, and a lower population density than the smaller instars. Try to keep their enclosure clean; prevent pathogens such as mold from growing in there. Try giving them fresh leaves, and replace the leaves before they have a chance to dry out. If you managed to raise them to this point, I will say: well done! This species can be a headache for some breeders. The most difficult part is soon over.

Oh, and did you know that they have a butt smiley? That’s right; this is some extremely important entomological information right here. But seriously though, on their behinds, they have a marking that resembles a smiley. Kim Kardashian should honestly quit her job, because THIS is about to be the worlds most famous butt soon.

Please pay attention! Callosamia promethea spin their cocoons, sometimes perfectly hidden within the leaves. It’s very easy to not notice one, and to accidently throw it away. Don’t let this happen to you! They will often fold a few leaves, using silk strings, and spin a cocoon inside the cavity. Typically, their cocoons are attached with a silk string or ‘pad’ that reminds us of other species, like Samia cynthia, or even some Antheraea and Rothschildia species perhaps – that firmly attaches the cocoons not only to the leaves, but also the stem of the plant. It is said that these cocoons are easy to spot outdoors in winter in the U.S.A, for the silk that suspends the cocoon prevents the leaves from falling to the ground; and within these suspicious autumn leaves, cocoons can be found.

Unfortunately, Callosamia promethea is univoltine (or single brooded) in most of its range. Even in populations that can have a second brood, it appears that the second brood is only partial. This means that in captivity, we usually have to store the cocoons for 8 to 10 months before we will get to see our moths!

It is not recommended to hibernate the cocoons by putting them cold straight away (such as in a refridgerator) – because there is a small chance that they could still hatch the same year, especially in very warm years. Instead, I would recommend keeping the cocoons at room temperature up until autumn, exposing them to the same temperatures they would experience in the wild, and then gradually lower the temperature. In the wild, they can surive cold temperatures up to -20C in winter (not recommended in captivity).

They are best overwintered outdoors, preferably in a well isolated box (isolate it with towels, vermiculite, cotton wool, or dry moss). They are cold hardly and seem to survive frost pretty well, but despite that, it’s best to protect them from freezing temperatures if you want a good hatching ratio; around 0C-10C should be perfect.

Please keep in mind that the cold temperatures they experience during hibernation are a biological requirement! Some people may want to “protect” the cocoons from cold winters, but if you keep them too warm, the diapause will never be broken, and the cocoons will indefinitely remain dormant. It is a long cold spell followed by an increase in temperature that breaks their dormancy and triggers them to develop! No cold, no moths.

Well done! If you have followed these instructions; you should soon have your own moths. But there is one thing left to do: pairing them.

Pairing this species can be easy, but keep in mind that this species needs warmth and sunlight to pair. Just like butterflies! The males are diurnal, and they fly from late afternoon to sunset. In order to pair this species, it is recommended to put a couple of males together with a female, in a well-ventilated cage made from netting or gauze, in a sunny place in the afternoon. If it’s warm and sunny enough the males will become active, and start pairing.

Unfortunately pairing this species can be a little weather dependant, and in dark and cold weather they may not pair well. The good news is that this species is easily handpaired, which makes bad weather less worrisome for breeders.

The eggs of this species are easily collected in a petri dish and incubated at room temperature. Misting them is optional, but helps. Good luck! Was this caresheet useful to you? Then consider sponsoring us. This website is crowdfunded, and it aims to be the biggest website on the internet when it comes to the life cycles of Saturniidae and other moths – and in 10 to 20 years time it certainly will be. It is thanks to your sponsorship that I can keep developing hundreds of caresheets for free on the internet!

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Citations: Coppens, B. (2021); Written by Bart Coppens; based on a real life breeding experience [for citations in literature and publications] 

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