Perisomena caecigena — “Autumn Emperor Moth”

Perisomena caecigena, also known as the Autumn Emperor Moth, is one of the lesser known species of Saturniidae from Europe. This beautiful insect has soft pastel colours; ales are light pink and yellow; while females are rusty orange/brown.

Perisomena caecigena (male)

This species is found in South-Eastern Europe and is reported in Italy, Austria, Hungary, Slovenia, Croatia, Serbia, Albania, Ukraine, Romania, Bulgaria, Greece, Turkey, Georgia, Armenia and Azerbaijan. Beyond that, it seems to have one distinct / isolated population in Lebanon/Israel (Upper Galilee) and also one in Cyprus (Troodos Mountains). The population in Cyprus has a unique endemic subspecies! Perisomena caecigena stroehlei. They are reportedly abundant in the balkans.

Perisomena caecigena (female)

This species has adapted to flying in the cold weather in autumn! Reportedly their flight time is peak around October (September-November) when night time temperatures can become quite low; often between 0C-15C. This classifies them as a rather cold hardy species of Saturniidae! It also explains their autumn leaf camouflage.

The lifespan of this species is rather short. I documented imagoes living as little as 2-3(!) days – especially after mating, both males and females die rather quickly. When unmated they can last a little bit longer; especially virgin females (females live longer!) up to 5-7 days. Females have the tendency to immediately lay most of their eggs, the same night after she has mated with a male.

Perisomena caecigena fully grown larva (L4)

The eggs of this species of moth hibernate. They are laid in autumn, but do not hatch until spring. One of the most important food plants for this species is oak tree (Quercus sp); and thus, this species mostly tends to occur in woodlands and shrublands where there is plenty of oak tree available – such as dry montane oak forests or deciduous woodlands. Less frequently they also use other host plants such as beech (Fagus), hornbeam (Carpinus), poplar (Populus), pear (Pyrus), ash tree (Fraxinus), cherry (Prunus), willow (Salix). This species is found from lowlands up into the mountains (1400m).

Eggs of the caterpillars hatch in spring, and larvae feed on the young oak leaves. When fully grown the larvae are green, with yellow tubercules, from which long, white bristle like hairs emerge.

  • Difficulty rating: Average – Larvae like to be kept warm, a little humid but also well ventilated. Oak tree is highly recommended. Rearing is not very hard but basic experience is recommended. Pairing is slightly trickier. Eggs MUST be hibernated at cool temperatures!
  • Rearing difficulty: 5/10 (From egg to pupa)
  • Pairing difficulty: 6.5/10 (Archieving copulations)
  • Host plants:  Oak tree! They really prefer various species of oak (Quercus sp). Other than that, less frequently they also east other host plants such as beech (Fagus), hornbeam (Carpinus), poplar (Populus), pear (Pyrus), ash tree (Fraxinus), cherry (Prunus), willow (Salix).
  • Natural range:  This species is found in South-Eastern Europe and is reported in Italy, Austria, Hungary, Slovenia, Croatia, Serbia, Albania, Ukraine, Romania, Bulgaria, Greece, Turkey, Georgia, Armenia and Azerbaijan. Beyond that, it seems to have one distinct / isolated population in Lebanon/Israel (Upper Galilee) and also one in Cyprus (Troodos Mountains). The population in Cyprus has a unique endemic subspecies! Perisomena caecigena stroehlei
  • Polyphagous: Yes, accepts many plants
  • Generations: Univoltine. One brood a year; eggs always hibernate
  • Family: Saturniidae (silkmoths)
  • Pupation: Cocoon (silk encasing)
  • Prefered climate: Temperate. Larvae prefer warm temperatures; adults are very cold adapted.
  • Special notes:   Eggs do not hatch unless stored cold for several months!
  • Estimated wingspan:  55mm-85mm (a smallish to medium sized Saturniid )

The eggs of Perisomena caecigena can easily be hatched around room temperature. But one important condition needs to be met: the eggs have an obligate hibernation. In the wild, eggs of this species hibernate from October to April-March. During this time, cold temperatures suppress their their development. In captivity, it is recommended to store the eggs cold (but preferably frost free?) for 5 to 7 months. The best time to warm them up is when their most important host plant (oak tree!) has grown nice young leaves.

Perisomena caecigena eggs
Perisomena caecigena rearing container
Perisomena caecigena L1

The eggs of Perisomena caecigena are oval, creamy white, and covered with dark brown/blackish freckles. They remind me of mini quail eggs! In captivity, store the eggs around 4C-7C preferably for several months and protect them from frost. I, the owner of this website, live in the Netherlands (outside the native range of this moth); yet I was succesful in overwintering the eggs outdoors in a plastic microcentrifuge tube that I poked small ventilation holes into, that I placed within a secondary larger plastic container. Although my hatching rate was not optimal (it was near 50%) it was acceptable to me.

The young caterpillars are black, with orange tubercules and small white bristles (they honestly look quite similar to Saturnia pyri in L1!). They enjoy the young and tender oak leaves in spring. I raise the first instars in airtight plastic containers, with generous amounts of moisture-absorbing paper towels, and a small branch of oak lives in a tube of water to keep the leaves hydrated .

Perisomena caecigena L2
Perisomena caecigena L2

The second instar is quite distinct! The larvae become grey/black in colour. They shed from the first to second instar quite fast; often within a week.

In early L3 the larvae are grey, but they are green in late L3. How does that work? Well it’s simple – they probably start producing the green pigment over time after they shed from to L2 to L3. So don’t be suprised if they start out grey-ish, then become yellow-ish, and then finally become green in a number of days.

Perisomena caecigena L3
Perisomena caecigena L3 / early L3 (grey) and late L3 (green)
Perisomena caecigena L3 ready to molt

So how many instars does this species have? I must be going mad; but every time I raised them, I only counted four (4) instars. That’s a bit unusual; although instars in Saturniidae often vary, most species have 5 instars (some even 6 to 8). But it really did seem that my larvae cocooned near L4 each time! I looked into literature, and some sources report 4 instars, and other sources report 5 instars. Huh. Odd. Could it be an oversight?

I’m going to assume this species only has 4 instars as per personal observation.

In the final instar (L4!?) the larvae have a soft, mint-green tint, yellow tubercules. Sometimes the yellow tubercules are surrounded by colour blue. The spiracles are brown, and larvae have long white bristle like hairs.

Perisomena caecigena L4 (final instar)
Perisomena caecigena L4 feeding
Perisomena caecigena L4 rearing succes

Perisomena caecigena L4 feeding
Bart Coppens approved rearing setup for Perisomena larvae; large branches of oak tree in a plastic container (bottle, soda can) with water to keep the leaves fresh. On the bottom is paper towel to keep it easy to clean. Between the lid I placed netting to prevent escapes. I poked tiny ventilation holes in the lid. Despite the small ventilation holes, it is a humid setup(!)

Oddly enough, many online sources claim the larvae need a dry environment. My experience has been the opposite. I have had a lot of succes raising this species in almost airtight plastic containers with high humidity and not too much ventilation – I raise mine in rather humid conditions! I’m confident enough to say, based on my breeding experience, that the larvae do not mind (and maybe even like!) high humidity. Instead, I believe warmth is more important. They’ll survive around 20C (room temp), but if you warm them up to 23C+, they just become a little bit faster, bigger, healthier and more active.

Do not expect the larvae to grow very big; Perisomena caecigena is a smallish Saturniidae. The larvae are usually just a bit smaller than larvae of Saturnia pavonia. While the moths have larger wingspans, this short lived, cold adapted species seems to have a lower biomass (smaller lipid reserves too as imagoes?). Good sized larvae are between 4 and 6 centimetres in size if fully grown.

When fully grown, the larvae spin cocoons. The structure of silk reminds me of a mesh; it is thin and has many (ventilation) holes.

Larvae seem to have two cocooning strategies; they crawl to the floor and spin in leaf litter (in captivity, they like to use paper towel, moss, or dry leaves if you provide some!). A small percentage of larvae will find a higher place to pupate – typically hidden between the leaves.

In the wild, the species reportedly cocoons in leaf litter too, or near the base of trees and host plants (but probably in the trees too in some occasions; as some larvae in captivity were observed looking for higher points to cocoon hidden between the oak leaves).

Perisomena caecigena cocoon
Perisomena caecigena male pupa
Perisomena caecigena cocoon harvest

The cocoons of Perisomena caecigena follow a simple routine. This cold adapted species flies in autumn in Europe. Larvae pupae around May-July (depending on location). The cocoons then oversummer through the hottest time of the year. And in autumn, when the days become shorter, temperatures become cold, and leaves start to fall – the moths emerge.

In the wild, most moths emerge around October. I suspect the pupal development is triggered by environmental cues – especially cooler temperatures. Why? Because in captivity, if kept artificially warm, the cocoons can become confused – which results in moths eclosing around December/Januari sometimes (this would probably never happen in the wild). I suspect the moths emerge faster if they are gradually cooled down in late summer. It would make sense!

In autumn and winter, temperatures can quickly become so cold that they are lethal to insects – even to a cold hardy species like Perisomena caecigena. At the same time, flying in autumn probably has advantages to a moth – such as fewer nocturnal predators (for example, many bats – the mortal enemies of moths – begin to hibernate as temperatures start to drop below 10C!). So their timing needs to be just right – which is to emerge in autumn when it’s starting to become colder – but before there are serious frosts that are harmful to the moths. And so they have to rely on environmental cues, especially (probably) the dwindling temperatures. Therefore, it is a good idea to simulate an autumn and if possible, keep the cocoons at lower temperatures after September.

Perisomena caecigena are unusual moths, in a sense. They are the only Saturniidae in Europe that fly rather late in the year (unless one counts the introduced species Antheraea yamamai, but even they don’t fly that late – or Neoris huttoni that is technically more Central Asian than European). Not just that, but for a moth with a respectable wingspan they are very short lived.

Especially after mating, both males and females pass away quickly. Mated males and females tend to pass away after 24 hours. This gives the moth a lifespan of 2-3 days(!). – Unmated moths can live a little bit longer; virgin males can last 3-4 days and virgin females up to 6-7 days in some cases. Still, it’s a very short life for a moth of this size.

The mating is very short and hard to observe. Some reports indicate it may last from 20 minutes to 2 hours (although I have no reliable source for this). That being said, breeders of this insect rarely photograph pairings it seems – blink and you’ll miss it.

Perisomena caecigena male & female
Perisomena caecigena male & female
Perisomena caecigena male

Perisomena caecigena are beautiful insects. Generally males are yellow and females are brown. There is a small amount of variation.

Males are always yellow, but their shade of pink can vary. Some specimens have beautiful pastel pink lines below the submarginal line on their wings. Other males are plain yellow, with no pink.

The female varies a little more. In most cases females are brown; this varies from a rusty, coppery, almost pinkish red-brown to sometimes a lighter, ochre yellow/brown shade. In some more rare occasions however, females can also have a bright yellow colour form that looks almost identical to the males (and could be confused with males if not for the antennae giving it away!). Despite that, I have reared this species several times and was never able to produce yellow females (but I have seen unmistakeable pictures of them) – perhaps this form is rare or localised.

Perisomena caecigena female
Perisomena caecigena female
Perisomena caecigena female face UwU
Perisomena caecigena male

I mentioned it too many times already – the species is cold hardy. I’ll mention it again. In the wild, they’ve been observed around temperatures of 15C-2C. So when placed outdoors near October, there is a good chance they will still pair when exposed to gentle autumn temperatures.

It’s hard to tell if the moths have actually paired because 1. the pairing lasts for a short time and is hard to observe and 2. the eggs hibernate until next spring; so waiting a few weeks to check for larvae is no option.

Typically after mating though, females will lay a large volume of eggs in one night – neatly laid in rows. Prolific egg laying is often a sign of fertility. Pairings are not super hard; but difficult to control and observe (and their short lifespans make it tricker).

If you do obtain fertile eggs – hibernate the eggs until the next spring. Good luck! I hope you enjoyed reading my article. This amateur website documents hundreds of moths – and costs a lot of time and server space to maintain. Consider helping us out! More details below.

Perisomena caecigena male

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Citations: Coppens, B. (2022); Written by Bart Coppens; based on a real life breeding experience [for citations in literature and publications] 

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