Aurivillius aratus is a very common species of silkmoth found throughout most of tropical Africa; they are commonly found in savannah-forest mosaic (“a transitory ecotone between the tropical moist broadleaf forests and the drier savannas and open woodlands”) and the moths seem to feed on a wide range of forest and forest edge plants, that are scattered into the grasslands bordering forests. While it is polyphagous and feeds on a variety of trees, it seems to greatly prefer plants from the “pea-family” that are common and can dominate the landscape in Africa, such as the many types of Albizia and Acacia, but it also feeds on some other secondary common types of shrubbery . The moths are very beautiful, with a highly detailed pattern of curved brown stripes, bright yellow wings and two fierce red eyespots on their hindwings.
The moths are found in most tropical African countries south of the sahara, from around the equator all the way to South-Africa. Although this species looks very conspicuous, they can be hard to ID sometimes, as there are a few other similar looking Aurivillius species present in the region, such as the similar looking Aurivillius fuscus (Westwood, 1849) and Aurivillius triramis (Rothschild, 1907). It is currently unclear how the ranges of these similar looking species overlap and where they replace eachother or cohabit – the adults can be hard to tell apart, although they are different species based on the appearance of the larvae, morphology and DNA.
Aurivillius aratus is a quite variable species, and they can vary from bright yellow to rusty orange to dark yellow. Their brown markings also vary from very light, almost pinkish brown to dark chestnust brown. It is a medium sized species.
- Difficulty rating: Moderate – You will needall the basic knowledge and experience. While it is not hard to be succesful, you will need to do a little research in order archieve succes.
- Rearing difficulty: 6.5/10
- Pairing difficulty: 7/10
- Host plants: Ricinus communis (castor bean), many species of Albizia sp. (mimosa); Acacia sp. (wattle) Robinia pseudoacacia (black locust), Salix sp. (willow), Ligustrum ovalifolium (privet), Fagus sylvatica (beech), Quercus robur (oak), Psidium guajava (guave), Parkia biglobosa, Piptadenia buchanani, Peltophorum africanum. In the wild, it predominantly prefers to eat plants from the Fabaceae (pea family) over other plants.
- Natural range: Supposedly found in many countries in tropical Africa: Angola, Cameroon, Central African Republic, Chad, Congo, DRCongo, Equatorial Guinea, Eritrea, Gabon, Ghana, Kenya, Malawi, Mozambique, Nigeria, Sierra Leone, South Africa, Tanzania, Togo, Zambia – although literature may confuse similar looking species that in reality do not overlap
- Polyphagous: Yes, especially on their preferred food – Fabaceae plants
- Generations: Multivoltine. About 2-3 generations per year.
- Family:Saturniidae (silkmoths)
- Pupation: Naked pupa, underground
- Prefered climate: Tropical environments
- Special notes:
- Estimated wingspan: 70mm-110mm
- Binomial name: Aurivillius aratus (Westwood, 1849)
The eggs of Aurivillius aratus are round and transparent yet milky green or yellow. They hatch in 8 to 14 days after being laid by a female. After this, small yellow caterpillars with black head capsules and a black stripe on their backs hatch from the eggs, only to form small groups on the leaves of the host plants. While the caterpillars of this species are gregarious, they do not form tight groups such as genera like Automeris (Hübner, 1819) – instead they prefer to stay in the vincinity of eachother, but their bodies do not directly touch and even in group gatherings they keep distance from eacother. The first instar lasts less than a week. For the best result, Fabaceae should be used (Acacia, Albizia, Robinia), although alternatives are acceptable.
The second instar is green, with stripes, orange tubercules and two black prothoratic setae and a green head capsule. The first two instars are very easy to raise in plastic boxes. I raised them in plastic cups, that had the lid removed and replaced with panty stockings (any ventilated net will work). I let the containers dry outcompletely to the air every day, while spraying them with water every morning. This consistently kept them wet and humid, without a high relative humidity that lingers in the container.
It’s the third instar where the caterpillars become really impressive. In this instar, they develop bright golden metallic patches on their backs, that are iridescent and strongly reflect light, almost like gold. In the third instar, the shiny caterpillars remain semi-social although they don’t form very big groups anymore. Still, it’s common to see clusters of 3 to 6 caterpillars feeding side to side simultaneously on the same leaves, and shed their skins together too. From this instar and beyond, they can be raised in a fauna box, or rearing cage. It does appear that this species is a bit thirsty, and appreciates being sprayed once in a while to drink water.
In the fourth instar, larvae become completely solitary, and in this instar they prefer to be alone. Don’t overcrowd them. They will still tolerate eachother however, but not in big groups anymore, so it’s good to upgrade them to bigger boxes and cages with fewer caterpillars per container, so they may have a more stress-free environment. The metallic on their backs seems a bit variable, and some caterpillars have it on each segment, only a few, or none at all in some cases.
In the fifth and final instar, caterpillars are 4 to 6 centimetres long. They take about 1.5 to 3 months to reach this size, strongly dependant on temperatures and food plant quality. It appears this moth can be raised at cooler temperatures outside of Africa, as low as 18C+, although this will significantly delay their growth. Their optimal temperature is much higher, around 25C+ (tropical Africa), and if you are able to provide them this temperature, you will notice much faster growth and more healthy individuals, and less mortality. A setup with a little extra heating is recommended if you live in a temperate climate (but not absolutely necessary).
When fully grown, caterpillars will develop a red/brown hue, and begin wandering on the floor. When they want to pupate, they will burrow underground to build a hollow chamber in the earth to pupate in; usually they seek crevices and leaf litter, or other openings that allow them to enter the soil easily. The caterpillars of Aurivillius aratus will easily pupate if provided slightly moist (not wet!) soil or peat, or plastic boxes with layers of paper towels.
Pupae should be stored underground, in a substrate that is easy to escape for freshly hatched moths; vermiculite, perlite, or (sterile) earth (not sand) can work well. When kept warm (21C+) moths will usually hatch from the pupae in 2 to 3 months time, and they tend to be continuously brooded in captivity, although it is likely the species is able to diapause in the wild depending on the local microclimate. While this species doesn’t fly in places where cold winters are experienced, there may be local dry seasons, and the flight time of the imago coincides with the rains. Diapause is possibly regulated by environmental factors such as barometric pressure, daylength and humidity instead of temperatures.
It looks small? Yep! That’s normal. Aurivillius aratus is a medium to small(ish) moth considering the family and tribe it is placed in (Bunaeini; Saturniidae) that are generally huge moths including genera such as Pseudimbrasia, Athletes, Bunaea, Lobobunaea and other giants. Depending on the species, their wingspans are often between 70mm-110mm. Still a big moth, just not as big as most of it’s cousins. Their colours can be very light and soft or dark and intense, and individuals seem to vary per brood.
Although I only managed to pair this species once, pairing them in captivity is very possible. The pupae seem to hatch more synchronised than other African Bunaeini that hatch very sporadically. That being said, it’s certainly not very easy to pair them. The moths require some ventilation, but if you can provide it, also warmth. Do not overcrowd them and pair them in medium size cages.
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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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