Pseudimbrasia deyrollei — “Deyrolle’s emperor”

Pseudimbrasia deyrollei is a very large species of Saturniidae moth from Africa. Pseudimbrasia deyrollei in fact is often claimed to be the largest moth that can be found in the entire mainland of Africa. While I have some doubts about this statement, especially since there is not much extrensive data about the average wingspans of most African Saturniidae – I think I happen to know some of the largest Athletes, Pseudobunaea and Epiphora species that can potentially compete with them –  it can not be denied that they are indeed a large and impressive species, and certainly among the largest moths that can be found in Africa, with wingspans up to 19cm.

Pseudimbrasia deyrollei males

It is easy to distinguish the males from the females. Females have a transparent window in the forewings, have rather triangulate and straight forewings, and have no tail on the hindwing. Males do have a tail on the hindwing, are more slender and have slightly curved/falcate wingtipes, and are smaller. The moths emerge at the start of the rainy season – their emergence is triggered by the increased humidity and temperatures, after the first heavy rainfalls. Data suggests they can have two to three broods a year if the conditions are right, although pupae have the ability to remain dormant for months if not years(!) if not provided the correct humidity and temperatures. In the wild, this rarely happens, but in captivity it may take a lot of care and patience to hatch the pupae and synchronise the emergence of the adults.  After hatching from their pupae, males patrol the area, looking for the airborne pheromones emitted by a female. Once they smell the pheromone, they locate her and pair, after which she lays 50 to 200 round brown eggs. Eggs hatch in a few weeks time. The young caterpillars are social and live in groups, but the mature caterpillars become solitary. They seem to be polyphagous and feed on a  variety of plants, but have a preference for tropical legumes (Fabaceae) such as Erythrophleum,  Tamarus, Acacia and Albizia.  Despite that they have been recorded on Sapium, Quercus (oak), Prunus (cherry) and a broader variety of plants.

Adults are well camouflaged in their resting position, appearing rather like a piece of tree bark or a dead leaf. It is only after being disturbed that they raise their forewings, revealing two threatening red eyespots on the hindwings. Mature caterpillars descend to the floor from their host plants, and burrow in the soil to pupate underground. Here, the pupa lies dormant for until it senses the start of a new rainy season.

Pseudimbrasia deyrollei male, resting position

Pseudimbrasia deyrollei, female

  • Difficulty rating:  Moderate (More difficult than average)
  • Rearing difficulty: 6.5/10 (From egg to pupa)
  • Pairing difficulty: 8/10 (Archieving copulations)
  • Host plants: Erythrophleum, Sapium, Acacia, Quercus (oak), Prunus (cherry), likely feeds on a wide range of tropical legumes and deciduous trees and shrubs. 
  •  Natural range: Africa, including but probably not limited to Angola, Burkina Fasso, Cameroon, Central African Republic, Chad, Congo, DRCongo, Ethiopia, Gabon, Gambia, Ghana, Guinea, Ivory Coast, Malawi, Mozambique, Nigeria, Senegal, Sierra leone, South Africa, Sudan, Tanzania, Togo, Uganda, Zambia, Zimbabwe.
  • Polyphagous:   Yes, has been recorded on Fabaceae, Fagaceae, Rosaceae, Euphorbiaceae and quite likely much more common types of shrubs and trees. 
  • Generations: Multivoltine – multiple generations a year, depending on the conditions
  • Family: Saturniidae (silkmoths)
  • Pupation:   Subterranean
  • Wingspan: 135mm – 190mm 
  • Binomial name: Pseudimbrasia deyrollii (Thomson, 1858)  — *Note: the original description really described them as ‘deyrollii’ and not ‘deyrollei’. But this is likely to be a spelling mistake as the name was  intented to be deyrollei, not deyrollii. 

Eggs of Pseudimbrasia deyrollei are about three millimetres in size, round and mainly brown. A paler creamy white/brownish ring runs along the edge. Eggs hatch in a few weeks time.

Pseudimbrasia deyrollei, eggs

The first instar caterpillars are uniformly black and social. They will travel and feed in groups, and even shed their skins together in a group. In captivity, it is best to raise them in medium to large groups, as the social behaviour stimulates their growth and feeding habits – social caterpillars are hardly overcrowded.

The second instar is black, but has red legs and a red head capsule, and behaves the same way as the first instar.

First instar (L1) and a few second instar (L2) caterpillars, Pseudimbrasia deyrollei

Second instar (L2) caterpillars of Pseudimbrasia deyrollei

Pseudimbrasia deyrollei, L2 and one L3 larva 

The third instar seems to be somewhat variable. They have red tubercules, and variably coloured bodies. When shedding their skin from L2 to L3, their body is mainly black and white. But gradually over time they become more pigmented, turning orange and later greenish. This makes sense, since the fourth instar, the L4, has a green body. It could be that the cuticule (‘skin’) of the next green instar that is already forming below the current skin, causing a gradual increase of green pigmentation.

The third instar is still social, and will live together in groups.

Pseudimbrasia deyrollei, L3

Pseudimbrasia deyrollei, L3

Pseudimbrasia deyrollei, L3

From the fourth instar and beyond, the caterpillars become solitary, and will avoid other individuals.  Along their backs, metallic shiny patches can be seen along their tubercules, bright orange spiracula, a blueish/red head capsule, red legs, a green body covered with blue/white specks.

Instar 1 to instar 3 can be raised in closed, airtight plastic boxes. But instar 4 and 5 require more ventilation and appropriate airflow: suitable are cricket tubs, a cut branch of food plant in a water bottle, or a rearing sleeve. They are not difficult to raise if you have basic experience with African Saturniidae and remember to keep them dry (don’t feed them wet food or spray them directly) and clean, and do not overcrowd them, as the fully grown larvae become very big and are easily overcrowded.

Pseudimbrasia deyrollei L4

The fifth instar seems like an enlarged version of the fourth instar, and it has a similar colouration and features. The dots covering their bodies become light blue (cyan) however. It is interesting to note that the metallic patches on their backs seem to vary a lot per individual, and some of them never develop any metallic tubercules, or just very few of them.


Pseudimbrasia deyrollei L5

Pseudimbrasia deyrollei L5

Pseudimbrasia deyrollei L5

Pseudimbrasia deyrollei L5, nearly fully grown

When fully grown, the caterpillars become rather brownish instead of green. This is a sign that they want to pupate. When ready to pupate, larvae descend to the floor and will burrow in the soil – or any other substrate provided. In captivity, vermiculite, bird sand, or garden soil are suitable. Caterpillars are fully grown in 1.5 to 2 months time depending on the temperature and food plant quality.

Fully grown Pseudimbrasia deyrollei

Pseudimbrasia deyrollei L5, preparing to pupate. Prepupal caterpillars turn brown

Pseudimbrasia deyrollei pupation

The pupae of Pseudimbrasia deyrollei are though for they are heavily armored and have a thick layer of chitin. This enables them to survive drought and discourage potential predators from consuming them. The moths emerge at the start of the rainy season – their emergence is triggered by the increased humidity and temperatures, after the first heavy rainfalls. In captivity it may be difficult to simulate this. It is advised to keep them cooler and  very dry  for a prolonged amount of time – multiple months in fact –  and after that, to wake them up by suddenly keeping them warm and humid.

It is the sudden increase in temperature and humidity after a longer dry period that triggers them to develop, in this case the dry period and wet period are equally important, as the pupae are actually triggered by the actual increase in temperatures and humidity, and not just the warm and humid conditions alone, and thus they require contrast in order to simulate a dry and rainy season.  Data suggests they can have two to three broods a year if the conditions are right, although pupae have the ability to remain dormant for months if not years(!) if not provided the correct humdity and temperatures. In the wild, this rarely happens, but in captivity it may take a lot of care and patience to hatch the pupae and synchronise the emergence of the adults.

Pseudimbrasia deyrollei pupae

Pseudimbrasia deyrollei  male

Pseudimbrasia deyrollei female

After hatching, the adults live 7 to 20 days time, females longer than males. Pairing them in captivity may be trickly, as adults are able to hatch sporadically in captivity if not kept in the same conditions as pupae. Even if you a male and female of them at the same time, it may be tricky to get them to couple up. This species is very large, and their great wingspan gets in the way of pairing in smaller cages, for the moths seem to have problems with coordination inside medium sized pop-up breeding cages. Sometimes males have trouble locating the female for that reason, and it is also easy to overcrowd this species because of their size. Too many individuals in one cage will disturb and crash into eachother because of their great size, potentially disturbing pairing attempts made by other moths.

Pseudimbrasia deyrollei  males

Pseudimbrasia deyrollei underside

deyrolles.pngPseudimbrasia deyrollei 

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Citations: Coppens, B. (2019); Written by Bart Coppens; based on a real life breeding experience [for citations in literature and publications] 

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