Saturnia pavonia — “Small Emperor Moth”

The Small Emperor Moth (Saturnia pavonia) is perhaps one of the most well known and iconic species of Emperor Moths (Saturniidae). The bright orange and colourful males of this species can be seen erratically flying in early to late spring, especially on warmer spring days – hoping to locate a female that, while significantly less colourful [yet larger] than the males is equally of an impressive insect to observe. Together with Aglia tau, this species is one of the only native species of Saturniidae in much of northern Europe.

Saturnia pavonia female
Saturnia pavonia male

Saturnia pavonia is primarily found in heathlands, scanty grassland, woodland margins and shrublands – it is found in (Northern) Europe, throughout central Russia (from west to east) into the Far East (Northeast China), where it appears to occur rather seasonally. The moths typically fly from early spring (early April) to late spring (early June), although their activity peaks around the first weeks of May – although flight time varies based on latitude, altitude and local weather. This species only produces a single brood a year, as the cocoons hiberate.

The males of this species are diurnal (day-flying!) and generally become active in the afternoon. They have a fast, erratic, darting and zig-zagging flight pattern; during this time, it is their objective to find a mate (a female). The females of this species don’t move during the day, and wait passively for males to arrive.

After mating, the female will disperse and lay eggs. Interestingly, the females are nocturnal as opposed to the diurnal males (when it comes to flying) and at night she will find a suitable spot to lay eggs.

Saturnia pavonia caterpillars (L1)
Saturnia pavonia caterpillar (L5)

The young caterpillars (first few instars) are dark and highly social. They often travel and feed in small groups. As the caterpillars mature, they become solitary.

Fully grown caterpillars are incredibly beautiful and variable; generally speaking they are leaf-green with a variable amount of black pigment – often manifesting itself as black stripes or bands, but in some cases, also nearly completely black larvae – and colourful tubercles that are generally yellow or orange, but in some cases, bright pink or even pale white. Certainly, there are great differences to be seen in the appearance of individual larvae!

Caterpillars often browse the low vegetation in the understory layer, woody shrubs and herbs in heathslands/shrublands. They are very polyphagous for that reason. Some of their major host plants are heather (Erica sp.& Calluna sp.), blackthorn (Prunus spinosa), bird cherry (Prunus padus), Willow (Salix), Hawthorn (Crataegus), Blueberry (Vaccinium), Bramble (Rubus) and.. many more.

  • Difficulty rating: Average (Not hard to breed, but basic experience is recommended). The moths mate very easily and the pupae are super hardy! But larvae can be sensitive to diseases and humidity levels
  • Rearing difficulty: 6/10 (From egg to pupa)
  • Pairing difficulty: 4/10 (Achieving copulations)
  • Host plants: Often a heathland / grassland / shrubland species that not only feeds on several species of heather (Erica sp.) but also feeds on several types of plants one would typically expect to encounter within such environments and surrouding woodlandd edges such as bramble (Rubus), blueberry (Vaccinium), willow (Salix), cherries (Prunus), hawthorn (Craetaegus), Meadowsweet (Spiraea), birch (Betula), oak (Quercus), elderberry (Sambucus), elm (Ulmus), Arbutus unedo (Strawberry tree), hazel (Corylus), Salad burnet (Sanguisorba minor), Myrica gale (Bog myrtle). Most commonly used in the wild are heath and heathers (Erica/Calluna) and Rosaceae. on top of that, it has been reared on nonnative food plants such as sweetgum (Liquidambar), Peony (Paeonia), and others.
  • Natural range: Most of Northern and Central Europe (United Kingdom, Netherlands, Ireland, Belgium, Luxenbourgh, Northern Spain, Denmark, Austria, Slovakia, Slovakia, Czechia, Switzerland, France, Poland, Germany, northern Italy, and Scandiania –and from northwest Europe throughout Russia, into parts of Central & Western Asia such as Northern Kazachstan & northern Mongolia, northern Turkey, small parts of Armenia, into the far east – Yakutia (Russia) and even northern China. – Note: exact the distribution of this species is a little bit uncertain(!) due to there being several different, yet often extremely similar looking species. For example, in southern latitudes Europe it is gradually replaced by Saturnia pavoniella, or Saturnia josephinae in southern Spain. Where, geographically, pavonia ends and where pavoniella exactly begins, seems to be a bit vague at times. Generally speaking, it is thought that south of the Alps and Pyrenees, one expects to find Saturnia pavoniella instead as they are thought to be some of the geographical barriers that seperate the two.
  • Polyphagous: Very! In fact, caterpillars don’t seem picky and can be reared on a mix of food plants.
  • Generations:  Univoltine (one brood a year).
  • Family: Saturniidae (silkmoths)
  • Pupation: Cocoon (silk encasing)
  • Preferred climate: Mild temperatures. Early-ish spring species in Northern Europe, Russia, and even parts of the far East (China); the moths are active rather early in the year when it can still be quite chilly. Imagoes, cocoons and eggs tolerate cold temperatures although the caterpillars prefer to be a little warmer; eggs are laid in spring but larvae develop from spring through summer and thus enjoy increased warmth. Cocoons require a cold hibernation.
  • Special notes: Not hard to raise if you manage to find a balance between too humid and too dry (larvae like to be on the humid side, but also ventilated). Patience is required; cocoons always hibernate and hatch next spring! In some cases, the species can even hibernate twice or three times. Store cocoons cold in winter.
  • Estimated wingspan: 38mm-85mm; for a species of Saturniidae it is rather small. Females are significantly bigger than the tiny males, however.
  • Binomial name: Saturnia pavonia (Linnaeus, 1758)

Since this website has a focus on rearing moths in captivity, here is a breeding guide.

The eggs of Saturnia pavonia are easily incubated in small plastic containers, such as petri-dishes or empty food tubs. They generally need very little care and/or attention. Most people hatch the eggs near room temperature (21C) although they are more cold hardy; in spring females can lay the eggs in Northern Europe as early as mid-April (when the average temps are around 9C!). That being said, cold temperates generally prolong the development of the eggs – and if kept cold the development takes longer than the 2 weeks on room temperature.

Saturnia pavonia hatching from their eggs
Saturnia pavonia caterpillars – transferred to their first enclosure

The first instars are highly social, and will travel and feel in groups. In captivity, they can be reared in plastic boxes. Personally I’ve had the best results rearing them on willow (Salix) and hawthorn (Craetaegus) – although they can eat an incredible variety of plants! You can scoop the babies up with a paintbrush (don’t use your fingers, it may crush them).

The first instars can cope with higher humidity (no, you don’t have to spray them!!) in airtight plastic boxes with little ventilation.

Saturnia pavonia first instar (L1) – they are small, black and highly social.
Saturnia pavonia L1-L2 setup – food plant in a small water bottle to keep it fresh (Salix + Crataegus mixed) and paper towel to absorb excess moisture and condensation.

It’s possible to keep the food plant fresh by placing it in small bottles of water; just make sure to ventilate the enclosure sometimes, since this increases the moisture levels a lot. Too much moisture is not good.

Saturnia pavonia L2
Saturnia pavonia L2

In the third instar, I prefer to move them to larger enclosures. Providing a ‘generous’ amount of space is always a good idea, if you want to learn to breed moths.

Once again, actively regulate moisture by ventilating the container several times a day, or consider adding ventilation vents (cut large holes and cover them with mesh).

Saturnia pavonia L3 setup – food plant in a small water bottle to keep it fresh (Salix + Crataegus mixed) and paper towel to absorb excess moisture and condensation.
Saturnia pavonia L3
Saturnia pavonia L3

In L3 the caterpillars are pretty; and often a mix of black/yellow or black and greenish.

After the third life stage, I usually decide to give them more ventilation. Rearing them in plastic boxes without ventilation holes works for the ‘small’ caterpillars, but in L3 & L4 these conditions can make them sick; high humidity and no ventilation can lead to infections, diseases and mold that harms the larvae.

You can be a little creative here; cutting large ventilation holes in plastic boxes (and covering them with mesh) usually works.

This may be a bit unusual, but in this case I reared the larvae in a plastic plant propagator/incubator. While unconventional, it seemed to work. The slits allow for ventilation. Make sure not to house too many larvae per container! They become more solitary now, and while this species seems to tolerate high densities of individuals, it also makes them more vulnerable to disease.

Plant propagator with L4 larvae
Plant propagator with L4 larvae

In the 4th life stage, they turn green – usually with a hint of black (once again, they vary a lot). Most importantly, in this life stage they become mostly solitary and abandon their communal lifestyle! Change food and leaves regularily – do not let them dry out.

Ventilate containers well; don’t let too much moisture build up over time.

Saturnia pavonia L4
Saturnia pavonia L4

In the final instar, the Saturnia pavonia caterpillars become incredibly beautiful! Famously they have a form with pink tubercles; but usually they are yellow or orange. In this life stage they are solitary but still tolerate higher densities of larvae (especially in captivity) than most other silkmoths.

Saturnia pavonia L5

Saturnia pavonia L5
Saturnia pavonia L5

A bunch of nearly fully grown larvae on my hand. Great succes!

Saturnia pavonia L5

From egg to cocoon, it takes the larvae usually about 35 to 55 days. The rate of growth depends on the quality of the food plant (diet) and temperatures (the colder, the slower the development). On room temperature, it usually takes about 40 days for the first larvae to begin spinning cocoons.

Saturnia pavonia spinning a cocoon

The cocoons of Saturnia pavonia are intially white, but when they come in contact with moisture they turn brown (perhaps it starts a chemical reaction that activates the brown pigments).

The cocoons of Saturnia pavonia are oval, paper, and quite though. Interestingly they have a double layer – and an ‘escape hatch’,. Moths always emerge through the narrow tip of the cocoon, where the silk appears to be thinner so that the moth can break through it more easily.

Saturnia pavonia cocoons

The cocoons of this species must hibernate in order for the moths to emerge. It is only after experiencing a prolonged period of cold temperatures, that the development in the pupa starts (this, of course, after being warmed up again!). The hibernation is obligate. In captivity, the cocoons must be stored cold – preferably outdoors, if you live in a place with cold winters.

If, for whatever reason (maybe you are into rearing exotic species?) you are not in their native range, the cocoons can be hibernated in the refridgerator, or any cool place – ideally between 5C to 10C – for atleast 4-5 months. Otherwise, it is recommended to place them outdoors in a plastic container during winter. The cocoons and pupae of this species are very cold hardy; although it is wise to isolate them, as to protect them from hungry rodents [which are suprisingly apt at sniffing out, and gnawing open cocoons in order to consume the pupae].

Yes, I keep them outdoors in winter! Here’s the box I kept them in; I hid it in the bushes in winter. I added some dry sphagum moss for isolation; they can handle low temperatures no problem.

In spring, bring the cocoons indoors and warm them up. If you’re lucky the moths will come out!

Lucky indeed – since in some cases, the cocoons can decide to hibernate a second (and sometimes third) year; effectively taking 2 or 3 years before you get to see the moths you raised. Ouch. They can definitely test your patience. The good news is however, in the majority of cases this does not seem to happen (but it can, sometimes). Most of the time, it takes just one winter.

In spring, many of the moths emerge

The females are much larger than the males, and very easy to tell apart; they are grey and creamy white, and have thin, stringy antennae. They have plump and heavy bodies, that makes it harder for them to fly.

Males are small in comparison, but much more brightly colored. Their forewings are a bright, rusty brown-red colour while their hindwings are bright orange – and of course the males are thick feathery antennae.

This species is short lived; typically they live between 4 to 11 days. During or unfavorable or cold weather they may be more inactive which adds to their longevity. In warm conditions, males can exhaust themselves in mere days. Interestingly, the males are diurnal (day active) and typically fly during mid day and the afternoon. In some cases, large numbers of males are visible, flying erratically through heathlands, looking for females.

Interestingly, the female is nocturnal(!) and after the daily activities of the male, females fly at night in order to find suitable places to lay eggs.

Saturnia pavonia female
Saturnia pavonia female
Saturnia pavonia male
Saturnia pavonia male
Saturnia pavonia male

Once the male has located a female, the mating will commence. Mating takes a short time (15-45 minutes). Sometimes, the males will move on to find a second female. Males attach themselves to the female using the claspers on their abdomens, and will often cling to them.

In captivity, this species is generally easy to mate. They like airy conditions. In spring and summer, it is wise to place them outdoors in a net or pop-up cage. Light stimulates the males to become more active.

Saturnia pavonia mating
Saturnia pavonia mating
Saturnia pavonia males & females: mating enclosure

I mate them in ‘pop up cages’ that I suspend in trees or bushes on preferably dry and preferably sunny days in bushes or trees. [I live in the Netherlands, their native range]

Saturnia pavonia female
Saturnia pavonia mating

After mating, females can lay 100+ eggs in some cases. In captivity, this will happen rather easily – it is a matter of keeping them alive. They will scatter then through their enclosure. In the wild, females lay rings of eggs around branches of host plants.

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Citations: Coppens, B. (2023); Written by Bart Coppens; based on a real life breeding experience [for citations in literature and publications] 

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