Antheraea polyphemus — “Polyphemus moth”

Antheraea polyphemus, the polyphemus moth, is a very large moth found in Canada, North America and Mexico. It has a very large distribution and can be found almost everywhere in the United States; but is also found over the northern border of the USA into Canada and even over the southern border into Mexico. It is a very large and attractive species with brown forewings and two very detailed and realistic looking, owl-like eyespots on the hindwings. It appears to have conquered most of North America, where it is one of the most common ‘silkmoth’ (Saturniidae) species. It’s succes, it appears, comes from it’s ability to survive in a wide range of habitats and climates. From Canada, where the summers are short and winters can be very old (-20C or colder), to warm and wet subtropical Florida – to the hot, dry and arid Texas and Mexico. One of the ways it can deal with these different environments, is being able to eat many types of food plant. The caterpillars are quite polyphagous, and have an appetite for most common types of deciduous trees and woodland shrubs, including but not limited to birch (Betula), oaks (Quercus), maple (Acer), willows (Salix), cherries (Prunus), hawthorn (Crataegus), walnut (Juglans), sweetgum (Liquidambar), alder (Alnus), poplar (Populus), elm (Ulmus), Sassafras sp., tulip tree (Liriodendron), beech (Fagus), Gleditisia sp, , sumac (Rhus), Robinia sp., and more.

Antheraea polyphemus male

Polyphemus moths overwinter as cocoons. Pupae are able to postpone their development, and can enter a diapausal state that enables them to remain dormant for a long time. In this state, cocoons can survive very cold temperatures. When the moths decide to overwinter, varies a lot per geographical location. In their northernmost range, where the winters are bitter cold and summer is short, this species will play it safe and produce only one generation a year (Canada and the states bordering Canada e.g Minnesota) and cocoons immediately prepare for winter. However, the more we move southwards in their range, they gradually produce more generations per year. In most of the United States, they seem to produce two to three broods. In the most southern and hottest states such as Florida, Texas, Lousiana, they may produce three to four broods per year. While it may seem that different populations have different habits, this behaviour is actually not entirely genetic. The caterpillars of this species can accurately predict when winter is coming. They do this based on several factors such as ambient temperatures (is it getting hotter or colder?) and daylength (are the days becoming longer or shorter?) and possibly more environmental cues. This is why in captivity, cocoons can sometimes hatch in the middle of winter, or produce more broods than usual. In captivity, the caterpillars experience artificial temperatures, artificial light, and more, and may misjudge the time of the year, causing them to hatch at innapropriate times. This only happens if the cocoons are kept too warm though; cold will always suppress the cocoons and force them to overwinter.

Antheraea polyphemus L5

Because of their polyphagy and versatility, these moths can be common in urban areas including parks, suburbs, argicultural areas, gardens and orchards. Otherwise, they are commonly associated with virtually all types of forest,wetlands, swamps, and any place where deciduous trees are common. Caterpillars are a bright, almost flourescent (mint or lime) green with brown head capsules, orange spiracula and in some cases have white ‘stripes’ along their sides, and are decorated with ‘warts’ (tubercules) that are slightly hairy (setae); these tubercules can be brightly colored and are often orange, yellow, pink or red and are sometimes accompanied by shiny metallic patches. Caterpillars prefer to spend their entire lives on their host plants and are often hidden in the trees, and only come down when they need to spin a cocoon (or fall down by accident).

Polyphemus moths are easy to raise in captivity;  hobbyists that appreciate moths commonly breed them, and many American (amateur) entomologists / nature lovers / insect collectors have fond childhood memories of them. Interestingly, Antheraea polyphemus manages to be quite variable despite having the same basic colours and pattern. They come in many shades of brown, from sandy yellow to dark chestnust / olive brown. Their ocelli, pink stripes and black scaling also varies a lot. Because of this variability, some breeders have been able to select some of these traits and create very unusual looking moths – I have seem some completely black, but also nearly white individuals created by hobbyists.

  • Difficulty rating: Simple (Very simple to breed; keep caterpillars ventilated and clean) 
  • Rearing difficulty: 4.5/10 (From egg to pupa)
  • Pairing difficulty: 4/10 (Archieving copulations)
  • Host plants:  birch (Betula), oaks (Quercus), maple (Acer), willows (Salix), cherries (Prunus), hawthorn (Crataegus), walnut (Juglans), sweetgum (Liquidambar), alder (Alnus), poplar  (Populus), elm (Ulmus), Sassafras sp., tulip tree (Liriodendron), beech (Fagus), Gleditisia sp, , sumac (Rhus), persimmon (Diospyros), Robinia sp., and more.
  • Natural range:  Canada (south), North America (almost everywhere – except Arizona!), Mexico (north)
  • Polyphagous: yes 
  • Generations: Multivoltine  (1 to 4 generations)
  • Family: Saturniidae (silkmoths)
  • Pupation: Cocoon (silk encasing)
  • Prefered climate:  Temperate to subtropical
  • Special notes: Often bred by hobbyist for fun, since it is big and easy to breed. 
  • Estimated wingspan: 120mm-170mm
  • Binomial name: Antheraea polyphemus (Cramer, 1776)

The eggs of Antheraea polyphemus are oval, a little flat, creamy white/brown with a brown ring that runs along the side. They can easily be hatched on room temperatue, and caterpillars hatch from them in about 10-14 days time. The caterpillars will eat a part of their eggshell, start wandering a lot, and find a good place to settle down and eat.

Antheraea polyphemus babies

The baby caterpillars are easily raised in plastic boxes. Important is that they are not kept too humid (leaves evaporate water), but to combat this, they can be given a substrate of water absorbant paper towels, or given small  ventilation holes. Not adding too much leaves also helps keep the humidity down. A few great host plant options are oak (Quercus), birch (Betula), willow (Salix) and sweetgum (Liquidambar) for good result and nicely sized specimens, but any of the host plants mentioned before can work. Experimentation with food plants can give different and perhaps interesting results.

Caterpillars L3 and L2 mixed

In a matter of weeks, caterpillars become large and green. In this stage, after about their 3rd instar, it’s better to change the setup from plastic boxes to something more ventilated and less crowded. Caterpillar rearing sleeves work very well if you live in a temperate climate, but so do caterpillar rearing cages with cut food plant in a water bottle, or a plastic container with the lid removed and replaced with netting/mesh to enable good airflow.

Antheraea polyphemus caterpillars quaranted on Betula in rearing sleeves

Antheraea polyphemus L3/L4

In instar 4 and 5, the caterpillars become quite fat and chubby, and will start eating a lot of leaves. They are tolerant of being reared in high densities, as long as their containers remain clean and hygienic and they are allowed some airflow. Generally, diseases and infections tend to develop inside poorly ventilated containers with ‘stale’ air, that are overcrowded and too humid. Bacteria and fungi thrive in such an environments, and will cause diseases. They have a great appetite, and prefer fresh food at all times.

Antheraea polyphemus L4 and L5

Antheraea polyphemus L5

Some of my Antheraea polyphemus – easy to raise in captivity in higher numbers

The caterpillars are fully grown in 1 to 2 months time, depending on the temperature. Raising them outside in spring, which has very cold nights and days, takes them longer (2 to 2.5 month) than indoors on room temperature or in summer (1.5 month) before they spin their first cocoons. Generally, the warmer you keep them the faster they will grow, but don’t overdo it – it is still a species that comes from temperate and palearctic habitats, although they do tolerate (and appreciate) heat in some cases.

Before they spin cocoons, the caterpillars become a little restless and lose their interest in eating, and start wandering. In the wild, this is when the caterpillars are commonly found by people, since it is the only time they voluntarily leave their food plants (trees). They may wander for a day or two, before finding a good spot to spin a cocoon. Usually this is between the twigs and leaves of their host plant, but also between fallen leaf litter on the ground, on braches or crevices in tree bark and more. Some caterpillars turn dark green before pupating.

Fresh cocoons are papery and silky white, but over the span of a few days they harden and become thougher and become brownish.

Antheraea polyphemus fresh cocoons 

Antheraea polyphemus cocoon between birch twigs

The cocoons of Antheraea polyphemus can be stored at room temperature. Depending on the time of the year, they will hatch quite soon – often in about 4 to 6 weeks time. IF the cocoons do not decide to overwinter, that is. Overwintering cocoons hatch after they have experienced almost non-stop cold temperatures for about 5 months, and are then sponateously warmed up (as to simulate spring).

Antheraea polyphemus female

Antheraea polyphemus male and female

The adult moths live for about 7 to 15 days usually. They are unable to eat as adults, like most Saturniidae, and live their short lives just long enough to pair, lay eggs, and die. They are best kept in well-ventilated cages made from soft netting/gauze/fabric such as pop-up insect cages or pop-up laundry hampers.

Polyphemus moths I raised myself – I once raised over 70 in one generation!

Polyphemus moths I raised myself – I once raised over 70 in one generation!

Antheraea polyphemus male 

These large moths are easy to pair in captivity if a few conditions are met. The most important is ventilation; in order to locate the female, the male doesn’t just need to be able to smell her pheromone, he specificially needs to be able to tell where the smell is coming from: and this is only possible with good airflow. They are best paired in cages in front of an open window, outside, or indoors in a well ventilated room (turning on a fan in the room could help). The moths are nocturnal, and will pair in the middle of the night. In conclusion, they need a dark enclosure with airflow. In regards to temperatures, they are more tolerant, and seem to be quite active and will pair even during colder nights, and may be active at temperatures of 9 degrees Celcius or warmer.

Paired moths often stay together for about 24 hours, so it’s easy to see if they have copulated. Often, the male will be seen dangling below the female, firmly attached to her abdomen. After the pairing, he leaves her alone the second night, and females may lay 100 to 300 eggs.

Antheraea polyphemus pairing

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Written by Bart Coppens, based on a real life breeding experience. Citations; Coppens, B. (2019)

 

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