Antheraea godmani — “Godman’s silkmoth”

Antheraea godmani is a legendary animal. Out of the four Antheraea species currently described on the American continent (polyphemus, monetzuma, oculea, godmani) it is certainly the rarest and the biggest one. It is found in most of Central America from Mexico to Costa Rica, and likely all the countries in between (Guatemala, Nicaragua, El Salvador [unconfirmed], Belize, Honduras, Panama) and even a part of South America (Colombia). Here, they are restricted to the mountains; Antheraea godmani is a montane species encountered in higher elevations. They have been observed from altitudes of atleast 1300m up to 3600m and possibly higher.

Antheraea godmani male

It’s natural habitat is montane cloud forest. Cloud forests are a unique  and somewhat rare habitat associated with (sub)tropical climates, and are not to be confused with rain forests. Rain is formed when water evaporates once it is heated up by the sun, turns from a liquid into a gas, rises higher into the atmosphere only to cool down again when it reaches the colder, higher altitudes and condesates into clouds which in turn become saturated with too much water – and that creates precipation (it falls back to the surface in the form of rain for example!).  Cloud forests however, are located exactly on the altitudes where condensation happens. When hot and humid air with water vapour rises from low elevations, it cools down and creates condensation in the form of clouds when it meets colder, higher elevations. This creates heavy, thick clouds of fog that blanket the forest and saturate them with moisture. It is exactly these clouds that feed this unique ecosystem; the thick fog that envelops the forest can create a strong cooling effect and also create a very high degree of humidity. Temperatures are much milder than the hotter lowlands; with slighly warm days between 20°C-27 °C but colder nights around 5°C -15°C. Cloud forest species appreciate a combination of higher humidity combined with mild (but not intense!) warmth but also have to survive colder (but not freezing!) temperatures.

Antheraea godmani female

In these forests, it presumably feeds on oak trees (Quercus). While oak trees (Quercus sp.) are common elsewhere, in the tropics oak trees are somewhat rare and limited to highlands; this may explain why Antheraea godmani is restricted to these places as well. It is unknown if it feels on other types of host plant other than Quercus, and at the time of writing, is thought to be an exclusive oak feeder in the wild. In the places where it can be  found, it seems to be nearly continuously brooded, and adults have been seen for about  9 or 10 months of the year, only slightly avoiding the coldest time of the year but otherwise seemingly producing continuous generations.

Interesting about Antheraea godmani is their wingspan – the moths are quite gigantic – with wingspans up to 180-190mm – an absolute monster, outsizing its relatives such as polyphemus and montezuma by far. What is also interesting is that males are bigger than females; for the majority of the Saturniidae, the opposite is true.

Despite having a seemingly large range, not a lot of records of them are available. The reason is that Antheraea godmani is a bit of a rarity.  Of course, when it comes to biology, it is a bit dubious and questionable to think of animals in terms of being ‘rare’; the word has no biological meaning or intrinsic value at all. What it really means is that the animals are not frequently encountered by humans for various reasons; which may be because their populations are very localised for example, or their population ecology dictates that they live in low densities, or that they simply live in a habitat or environment  that is  hard to reach for humans.  In this case, it may just be that they live in habitats where people don’t commonly go to catch some moths. It may be worth mentioning however, that the moths are very much a collectors item, and are quite valuable to a passionate collector in monetary terms – not something I personally care about as someone that prefers to breed moths over collecting them (not that something is wrong with collecting; I encourage it, it is just not my hobby)- but it may be worth noting that often, one of the primary motivations of people that wish to raise them, is to produce some pristine specimens. 

  • Difficulty rating: Challenging – not a species recommended for a beginner; but also not too difficult for an experienced person. Caterpillars in particular are sensitive to disease. 
  • Rearing difficulty: 7/10 (From egg to pupa)
  • Pairing difficulty: 7.5/10 (Archieving copulations)
  • Host plants: Quercus; many types of oak tree including Q. robur, ilex, rubra, petrea and possibly many more
  • Natural range:  Central America from Mexico to Costa Rica, and likely all the countries in between (Guatemala, Nicaragua, El Salvador [unconfirmed], Belize, Honduras, Panama) and even a part of South America (Colombia) montane cloud forest (1300m-3600m). 
  • Polyphagous: Only a little. Accepts many types of oak (Quercus). 
  • Generations:  Multivoltine – continuously brooded
  • Family: Saturniidae (silkmoths)
  • Pupation: Cocoon (silk encasing)
  • Prefered climate:  Warm and humid days; but colder nights – cloud forest environment
  • Special notes:  The caterpillars love to drink water! Allow them to do it once in a while; from a spoon or bottle cap. 
  • Estimated wingspan:  150mm-190mm
  • Binomial name:  Antheraea godmani (Druce, 1892)

The eggs of Antheraea godmani are small, oval and brown. They will hatch in about 10 to 14 days. Hatching them does not require any special treatment other than room temperature. Spraying is not required, although a fine misting could improve the hatch rate.

Eggs in glass petri dish

Soon after the eggs hatch, the caterpillars must be transferred to a plastic box, that includes leaves of any type of Quercus sp. (oak tree). The first instar has white tubercules and black bands running over the body and a red head capsule. About 12 hours after hatching they will settle down on an oak leaf and begin eating.

Antheraea godmani L1

Antheraea godmani L1

The second instar of Antheraea godmani is fluorescent lime green, with a red head capsule and black dots. They can be kept in plastic containers.

Antheraea godmani L2

Antheraea godmani L2

After the third instar and beyond they become more typically ‘Antheraea’ like, with a lime green body and dark chocolate brown head capsule. From L3 to L5 their appearance is more or less the same, despite growing into bigger versions each time.  Some caterpillars have one single, small metallic silver patch on the side of their bodies, but this trait is not present in each individual.

Antheraea godmani L3

Antheraea godmani L3

The first three (or four, even) instars can be raised in plastic boxes. To maximise your succes, it is a good idea to not overcrowd them and keep the boxes clean, and free of condensation. From instars 3 and beyond, they can also be sleeved or raised in cages on cut branches of food plant, in a water bottle.

Antheraea godmani L4

Antheraea godmani L4

Difficult to raise? “Antheraea godmani is easy to raise dude!” is a statement I’ve heard too often. I disagree. Now, a discussion about if moth species is intrinsically easy or difficult to raise is probably useless, since there is no such thing as inherent difficulty, and each persons experience will vary a lot; what is difficult to me isn’t necessarily difficult to you and vice versa. How difficult to breed a species is also depends on in what country and climate you live, and how much it resembles the native environment of the animals. The truth is that caterpillars of Antheraea godmani are a little sensitive – and more demanding  – than the average Saturniidae.

This mainly relates to diseases. Antheraea godmani caterpillars seem to have a thing for becoming infected easily. And when that happens, they can infect eachother and the whole brood can collapse. There are numerous ways to combat this however. First: do not raise many of them together in one cage. Low density lowers the contact between animals and thus infection rates, but also lowers the build up of ‘dirt’ (feces) and harmful micro-organisms in one cage or container. Second of all, keep humidity low. I know I just spend a whole paragraph explaining they live in some of the most humid cloud forests – and the caterpillars actually love humidity. But so do bacteria and other pathogens. Dry and warm seems to work better. Last but not least, change the food plant often and keep it fresh, and do not handle the animals too often. If one looks sick, quarantaine it from the others.

They don’t seem to have other problems such as refusing to eat or growing too slowly. In fact, this species seems to be quite robust and tolerant to wider range of indoor temperatures and conditions – they just get sick really fast if you have bad luck. Otherwise they have very little performance issues. If you can prevent disease, you can probably raise them. However, their instability, sensitivity and sheer size does not make them a great beginner species. They are ‘easy to kill’, if they are neglected or overcrowded or stressed a little bit too much.

Drinking: currently, I have probably raised over a hundred of moth species in my life. And I never make an effort to let caterpillars drink. Most species get enough moisture from the leaves/plants they feed on! But Antheraea godmani caterpillars are really, strongly attracted to water. Many times I saw them crawl to the neck of the bottle I put the food plant in, to sip the water. Most caterpillars will enjoy drinking the dew drops from the leaves if they are misted, but this is the first time I have seen caterpillars actively crawl towards an open water source. Is drinking necessary for their survival? I don’t think so; like all other caterpillars they get enough moisture from the leaves. Does it help them? I think it does. Just don’t use a spray bottle to wet the caterpillars and the food plant, that is a recipe for diseases (unless it is really hot and the water can evaporate fast). Otherwise, you can offer them a spoon or bottle cap with water. They will probably appreciate it.

Antheraea godmani drinking

The fully grown caterpillars of Antheraea godmani are positively huge! I raise specimens up to 23 grams, but a personal friend of mine reported even bigger larval weights up to 27 grams in the final instar.

Antheraea godmani L5

Antheraea godmani L5

Antheraea godmani takes a long time to develop from egg to cocoons; the rearing takes about 2 to 2.5 months time. After that, they will begin spinning silk cocoons.

Antheraea godmani spinning cocoon

The cocoons have a very long silk pad, the longest I have seen so far. They are 12cm+ – but they do not “dangle” by this silk thread however. Most of it runs along the branch they made have spun their cocoons on. I conclude it must be a long “safety” line that keeps the cocoons in attached tree, even if the twigs they made cocoons on are broken. Therefore, I theorise that somehow, the cocoons of this species could be (?) vulnerable to falling from their host plants somehow, or maybe the wind/other animals snapping off the branches they cocooned on, and in response they developed these long safetly lines that attached them to the tree.

The cocoons of Antheraea godmani are oval, brown, and covered in white waxy powder.

Antheraea godmani cocoons

For a swift emergence, keep cocoons warm and humid. Moths hatch in 1 to 3 months time usually. They can be supressed if kept cold for a few months, around 5-7 degrees Celcius. While the moths never hibernate or overwinter in the traditional sense, it is possible to keep cocoons dormant and suppress them by keeping them at a gentle, cool temperature (no frost!).

The adults are huge – up to 17-19cm wingspan – and very impressive. It is possible to pair them in a well ventilated pop-up insect cage. They like warmer nights with a little breeze. Don’t put too many individuals in one cage; these large moths can and will disturb eachother. At most, try one female per cage, and one or two males.

Antheraea godmani male

Antheraea godmani male

Antheraea godmani female

Antheraea godmani female

Video:

Antheraea godmani male

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Written by Bart Coppens, based on a real life breeding experience. Citations; Coppens, B. (2019)

 

The aim of this website is to provide information about many species of moths and butterflies around the world, with a slight focus on rearing them in captivity.

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