Rearing & breeding Brahmaea hearseyi in the UK.

by Alan Marson, October 2004

Brahmaea (Bramophthalma) hearseyi male, Anhui, China,
courtesy of Alan Marson.

I have reared and bred several Brahmaea species (Owl moths) over the years. I don’t claim to be an expert but I have had some success so these notes may prove useful to other people rearing these species.

These notes apply particularly to Brahmaea hearseyi (which I have at the moment) but most apply equally well to B japonica, B wallichii insulata, and B tancrei. Where there are differences I have commented on them.

The ova: These are domed with a flat base. Fertile eggs develop a distinctive dark spot at the micropyle in the middle of the upper surface about two days after laying. As the eggs are close to hatching, the developing larva can clearly be seen inside the transparent eggshell. Larvae eat part of the eggshell, but it doesn’t seem to affect them if they are disturbed and don’t eat the shell. Mine hatched in twelve days – but this depends on the temperature.

The larvae: These have incredible ‘horns’ (modified tubercles) on the thoracic and caudal segments in instars 1 to 4. If the larvae are disturbed they whip these back and forth, and I suspect that these may offer some protection against parasitic wasps. In the 5th instar the horns are lost, but the large larvae are very colourful and striking. Given their foodplants, the larvae are probably distasteful to most predators.

Third instar

B hearseyi, like all the other species of Brahmaea that I have reared, readily accepted Privet (Ligustrum) and thrived on this as a foodplant. I understand that Brahmaea larvae are regularly found on Privet in China. I have also been told that they are found on Osmanthus species. (This is not surprising as, like Privet, it is in the Olive family – Oleaceae.) Apparently larger larvae of B tancrei will switch to Lilac and Ash (both of which are alternative foodplants for other Privet feeders). B hearseyi and other Brahmaeas will probably do the same. I haven’t tried this myself as I can easily obtain Privet.

NB: If you want their ‘horns’ to expand to their full glory, keep the larvae in containers where they can hang free and unhindered when changing their skins. Personally I usually rear them in plastic boxes. They are generally very easy to rear and can tolerate conditions that would be fatal to most Saturnids.

The larvae grow very rapidly. I find that although they do grow very quickly when kept warm, they also thrive in cool conditions. I suspect that even Brahmaeas from tropical countries mainly come from cool regions – i.e. at altitude. Mine took less than 3 weeks from hatching to ‘going down’.

Full grown larvae of B tancrei frequently make a ‘clicking’ noise with their mandibles when disturbed. I’ve not noticed this with B hearseyi or B wallichii.

Fifth instar

The pupae: I suspect that in the wild the larvae burrow under logs or rocks to pupate. In captivity they are reluctant to burrow in uncovered soil or peat. Larvae that are ready to pupate undergo a major colour change (almost always overnight) in a similar way to many Sphingid larvae. They can wander for a considerable time before settling to pupate.

I put a few inches of peat in a large box and cover it with several layers of newspaper. Then I spray the newspaper with water. Eventually the larvae burrow under this and settle down to pupate.

Storage of pupae: The other species that I have kept have all survived well when stored on peat in plastic boxes out in my garage or shed. B hearseyi has produced a partial 2nd brood with two thirds of the early brood emerging as moths in late August and producing another generation. The rest remain dormant. I intend to overwinter the pupae as above. Their native habitat is probably similar to that of B wallichii insulata in Taiwan and the insulata that I had some years ago did well under those conditions.

Adult moths: The trickiest part of breeding Brahmaeas in my experience, is in getting the moths to emerge properly and fully expand their wings. I have always failed to breed from imported pupae (including B wallichii from India) because I have not been able to get many of the moths to emerge successfully. The pupae seem to dehydrate easily and I think that this is the problem. In contrast I don’t have any problems in emerging my home reared stock.

For storage I keep the pupae lying on slightly damp peat. Then in spring, when emergence is imminent, I keep them on dry peat. Under damp conditions the pupal case doesn’t split easily and that can be just as bad as having the pupae dehydrated.

My B hearseyi always emerged overnight. On the first occasion five males emerged first (38 days after ‘going down’) and were joined after a couple of days by two females. Both of these paired in a cylindrical netting cage in my kitchen the first night after their emergence at around 11pm. They were still together when I went to bed after midnight but had separated by morning.

Brahmaea (Bramophthalma) hearseyi female, Anhui, China,
courtesy of Alan Marson.

In my experience all Brahmaea species seem to pair readily if healthy males and females are out together. Some species – such as B tancrei – remain paired the following morning. However, B hearseyi, like B wallichii, pair relatively briefly late in the evening and have separated by the following morning.

It's obviously best to observe a pairing to be sure of fertility of the eggs – but, as mentioned above, the eggs do develop a dark micropyle if fertile. If you have a female laying and suspect that she may have mated, keep the eggs for a couple of days and see if the dark spot develops!

Unlike Saturnids, the Brahmaeids do have a functional proboscis. In some species – such as B tancrei again – the proboscis is quite noticeable although small (short and ‘strap like’), whereas in B wallichii and B hearseyi it is very inconspicuous, just a tiny thread which is difficult to see. All species do appear to be capable of sipping droplets of water from the netting of the cage, but I doubt if they do any more than that. I have kept female B hearseyi alive for 20 days simply by daily spraying with a garden mist spray.

Brahmaeas are reputed to lay only a small number of eggs. Certainly the eggs are large for the size of the moth – especially as female Brahmaeas have relatively slender bodies. However, if the females are kept in good condition, they will continue to lay over a long period. To my surprise my B hearseyi eventually laid an average of 200 each. I think that the key is to ensure that they don’t become dehydrated.

Identification of Brahmaeas:

The Brahmaeidae seem to have been little studied. There is little about them in the literature and not very much on the internet. Two web sites to look at are http://www.silkmoths.bizland.com/Brahmaeidae.htm compiled by Bill Oehlke and http://www.wildsilkmoth-indonesia.com/brahmaea.html compiled by Ulrich Paukstadt. However, I think that there are a lot more species and detail to add as information becomes available. There are apparently 15+ species in China alone.

The Brahmaea species have some of the most complicated wing patterns of any Lepidoptera. The ones that I have seen seem to divide into two main groups. The ones that we tend to refer to as ‘Owl Moths’ which have circular ‘eye’ markings on their wings – such as B wallichii and B hearseyi – and the ones without these markings – such as B tancrei, B ledereri and B certhia. These main groups also appear to have other differences (such as the proboscis size mentioned above).

B wallichii (left) can be distinguished from B hearseyi (right) by the apical patch on the forewings.

In B hearseyi the inner band is smooth and arcs towards the body giving the apical patch an oval appearance.

In B wallichii this band arcs towards the wing tip and has a more jagged appearance.

Many South-East Asian islands have their own forms – many of which were previously regarded as races of B hearseyi. Genitalia studies have led to some of these now being given specific status – such as B celebica. The apical wing patches of the Japanese Owl Moth (B japonica) are similar to those of B wallichii and this species is now regarded to be a subspecies of B wallichii (i.e. B wallichii japonica).

Hopefully more species will become available to rearers in future years. They are certainly interesting insects to breed.

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