Also see Acrophylla titan.

Extatosoma tiaratum (also known as Macleay's Spectre or the Giant Prickly Leaf Insect) is a type of phasmid: a stick insect. This species is stockier than most stick insects, with many spines along their bodies and leg segments resembling dry leaves. Like other phasmids, they are herbivorous, and employ mimicry to avoid becoming lunch for other creatures.

I bought two of these, a male and a female, a couple of months ago and have been observing their wacky behaviour with great amusement. I've also been reading every piece of information I can get my hands on...much of it is very interesting, but spread out over many articles and websites. I intend to assemble a comprehensive guide to this particular species, including a care guide combining my own experience with other pearls of wisdom I've come across in my searches.

Contents 1 Mimicry 2 Moulting 2.1 How to tell if they are going to moult 2.2 Complications of moulting 2.3 Diary of moulting for Mr. & Mrs. Miyagi 3 Environmental requirements 3.1 Suggested enclosures 4 Flight 5 Eating & Drinking 5.1 Eating 5.2 Drinking 6 Reproduction & Breeding 6.1 Sexual dimorphism 6.2 Mating behaviour 6.3 Egg laying 6.4 Rearing the eggs 6.5 Care of hatchlings 6.6 Genetic diversity 7 Death 8 Generation 1.5 - A & B 8.1 25/04/2007 8.2 28/04/2007

Mimicry

The main defensive strategy against predators, or indeed, way of life for these insects is mimicry. Their appearance is the first line in this approach: they are typically the colour of dried leaves and several segments of their abdomens and legs are flanged in such a way thay the segments resemble dried leaves. They will sit motionless all day, occasionally swaying as though in a breeze. When threatened they will sway crazily or curl up their abdomens over their backs and raise their front legs in the air, putting on a fairly good impression of a big scorpion. The question of whether they are in fact impersonating scorpions is subject to debate, as scorpions and Extatosoma tiaratum are unlikely to encounter on another: the scorpions dwell low on the ground, whereas the leaf insects reside in the trees. The purpose of the pose may be just to look bigger and thus less attractive to a predator. Either way, it is scorpion-like enough. Apparently these insects were used instead of scorpions in the filming of one of the Indiana Jones films!

Mrs. Miyagi, a female E. tiaratum, shortly after reaching adulthood. Photo credit: Tristan Miller

The mimicry does not end with the grown insect, as the eggs themselves, which are flicked from the trees onto the ground, resemble seeds. The eggs are hard, apart from a little knob on the top called a capitulum. This contains a substance which is attractive to certain ants that live in the leaf insects native area. The ants carry the eggs into their nests, eat the capitulum, and discard of the rest of the egg inside their nest. Protected from predators and fire, the eggs hatch after several months. The behaviour and appearance of the newly hatched insects is very similar to that of the ants, so they are able to make good their escape and climb high into the nearby trees where they later moult into the more familiar leaf-mimics.

Moulting

Unlike verterbrates such as mammals, reptiles, birds and fish, insects do not possess an internal skeleton to give their bodies structure and rigidity. Instead they have their skeleton on the outside : their skin is like a suit of armour. The problem with this hard outer coating is that it does not grow as the insect does, so once in a while, the insect has to shed its old skin and inflate its new, bigger skeleton. This process is called moulting, and most insects have to do it at some point in their life cycle. For Extatosoma tiaratum, five/six moults divide their life into six/seven stages (called instars) as they gradually reach their adult size and form (there are differing accounts of how many stages there are). After each moult they are considerably (up to 2x) bigger than they were before!

The name of my insects are Mr. Miyagi and Mrs. Miyagi , for the male and female respectively. They have both lately reached their adult stage: moulting three times each in the time that I've had them. They moult approximately once a month. On two consecutive occasions the pair moulted at the same time, on the same day. Whether this is some sort of pheromonally triggered group survival behaviour, some sort of indication of shared genes or just pure coincidence I don't know. I certainly haven't read of synchronous moulting before, though that really doesn't mean a great deal: many of the sites dedicated to the study and care of these creatures parrot other sites and/or skimp on the details. I will investigate the behaviour further with the next brood.

Mrs. Miyagi during her moult into adulthood. At this point she has freed her head, thorax and most of her legs from her old skin. Notice the old skin in the upper sections of the photograph: the tail (through which can be seen the colour of the new skin) and the segments of the old legs rising up into the branches. The white strands seem to serve a structural purpose - apparently binding the insect's appendages in the correct moulting position until they have left the skin. A broken strand is visible in the centre of the photograph. Photo credit: Tristan Miller

How to tell if they are going to moult

I've only been lucky enough to observe a moult once: this was Mrs. Myagi's final moult. I watched her with paranoid eyes for days as the expected time for her moult drew near; every strange twitch or movement to me was that she was about to do it. I scoured the internet for any information on the topic, and came up virtually empty-handed. Finally one night she moulted right before my eyes, enabling me to not only witness this incredible transformation but also to make pre-moulting observations of behaviour and appearance.

The insect may stop eating for two or three days before moulting. It may also seem to stick to one position in the enclosure, usually high up as the insect must be able to hang its whole new body length (much bigger) in order to moult properly.

What I saw Mrs. Miyagi do was this: minutes before the moult began, she very purposefully turned 180 degrees so that her stronger back legs were higher up the sloping branch she was hanging from. This is completely at odds with any normal defensive mimicry she'd usually do.

The insect will then spend some time convulsing and pulsing, with the body segment just behind the head seeming to extend and shorten rhythmically. The skin around the thorax will take on an obvious white tinge, reminiscent of dead skin. As the insect continues to pulsate, this will spread to the legs and tail, where the skin may become bunched up. Soon the insect will emerge from the old skin, starting with the thorax, then the head, then legs, then most of the abdomen. It will then hang straight down from the tip of the abdomen (still caught in the old skin) until its new skin has inflated and hardened a bit. You may notice the claws are a lot paler than usual; they will darken as the skin hardens.

Once the insect feels ready, it will pull itself up to its old skin and liberate the tip of its abdomen. It will then spend some time hanging off of its old skin (still hanging on the branch), before eating as much of it as it can!

Mr. Miyagi happily munches away at his old skin after his final moult. Photo credit: Ann Clarke

Complications of moulting

The insect is very vulnerable during moulting: it's a delicate procedure and during much of it the insect's new skin is still very soft. If a moult goes incomplete, the insect will probably die, or at least lose a leg or two.

You needn't worry too much about startling the insect, as it will tend to continue moulting despite you staring at it or yelling to your very obliging friends to come and look. Handling the insect is definitely a no-no in this stage.

It is probably safe to assume that the insect knows what it is doing, so even if it looks like it needs help getting out of its skin, it probably doesn't. You should only risk assisting the insect if it is absolutly necessary, and if it doesn't involve touching the creature in any way. For instance, you might notice that the insect is not hanging freely: its legs are touching the ground more and more as it emerges. In this case you might very carefully move its perch to a higher position, bearing in mind that the old skin is quite brittle and must support the entire weight of the emerged insect. Generally, it is wisest to leave it be - it's natural to worry about your insect but you wouldn't want its death on your hands, would you?

Apart from not starting at a sufficient altitude, other causes of failed moultings are dehydration, malnutrition, interference from other insects, interference from humans, or just a lack of strength on the insect's part. Apparently severe inbreeding can also ruin its chances of reaching adulthood.

Diary of moulting for Mr. & Mrs. Miyagi

Mr. Miyagi

• First observed moult: 03/11/2005
  • Old size: 4cm
  • New size: 6cm
  • Notes:

• Second observed moult: 03/12/2005
  • New size: 8cm
  • Notes: Now has the beginnings of wings covering most of his thorax. More slender and antennae are longer than before.

• Third observed moult: 01/01/2006
  • New size: 12cm
  • Notes: Wings and wing covers extend to end of abdomen. Now very slender. Antennae are half body length. Three occelli now apparent on top of head.

Mrs. Miyagi

• First observed moult: 03/11/2005
  • Old size: 7cm
  • New size: 9cm
  • Notes:

• Second observed moult: 03/12/2005
  • New size: 11.5cm
  • Notes: Now has buds of wings.

• Third observed moult: 06/01/2006
  • New size: 16cm
  • Notes: Now has small, almost circular wing covers (elytra) over tiny wings.

Environmental requirements

• A dry, well ventilated enclosure that is roughly three times as tall as the adult length of the insect (to allow for successful moulting). Note that some people swear by low ventilation, but I've only ever seen it result in mould, fungus, drowned/mouldy insects and a tough cleaning job. My insects are robust and healthy, and have reached full size in a well ventilated reptile enclosure.

• Cuttings of foodplants standing in a jar or glass of water inside the enclosure. Foodplants include eucalyptus, rose leaves, raspberry leaves, brambles, even mulberry leaves. I've found that their absolute favourites are a few different eucalypt species, which makes sense as it is their native food. I've also heard that the insects will only reach their maximum growth potential if fed eucalypt. Either way, eucalyptus is easy enough to obtain from local parks. Present them with a few different types of eucalypt, that way they can decide what is the best. Also be sure to wash the leaves first, as they may have toxins from cars or pesticides on them. Replace every few days, or when eaten (the bigger the insect, the bigger the appetite, and the faster they eat!) As for the jar of water, make sure the top of it is blocked somehow so the insects can't accidentally fall in (especially important for the active hatchlings!)

• Sturdy, horizontal branches (becomes especially important as the insects reach adult size and weight) at various heights in the enclosure.

• Paper lined floor of enclosure: this is mainly to make it easy to remove faeces (dry and pellet-like) and eggs (more like seeds).

• The insects will appreciate having the inside of their enclosure misted with water from a spray bottle twice a day, or more in dryer weather. This helps raise the humidity and gives them something to drink. It may also help prevent the foodplants from drying out, which can happen astonishingly quickly in warm weather.

Friends! Have at least two insects in the enclosure, as they are social creatures. Remember though that the insects get rather large when fully grown, so plan ahead and get a nice, big enclosure if you're going to have a colony in there.

Suggested enclosures

From what I have read and observed, reptile enclosures are ideal for these insects: they usually have fine mesh on several sides, with removable roofs and glass sliding doors. They also have opaque sides, meaning the insects will have a choice of illumination as they move through the cage. The only drawback is cost, as a good size reptile house will set you back over $150.

A cheaper alternative which is probably better for several reasons is to make your insect houses out of clear plastic storage containers stood up on end. As containers come in all shapes and sizes, you can just about design the perfect enclosure for your needs. This method is also very inexpensive, the cost of materials should be under $15 for a good size enclosure. Just cut a big panel out of the lid, and fix flyscreen over it with superglue or even duct tape. Next cut another panel out of the top of the enclosure, and fix flyscreen over that. This will allow sufficient airflow, while keeping the insects happy as they like to hang from the ceiling (also a great position to moult from). Larger colonies will need larger containers (or extra enclosures) but these are all so cheap to manufacture you will become an avid breeder of insects in no time.

Glass aquariums are probably OK too, but one must avoid buildup of mould and fungus inside by cleaning regularly (without using cleaning chemicals!). One main disadvantage of these enclosures is that access to the insects can be difficult (as most aquariums have only one entrance at the top) - whereas the other two types will have access from the front over the whole height of the cage.

A temporary enclosure is also needed for the times when you clean out the main enclosure. A sheet of fine mesh over a bucket may do, but I'd recommend a small clear plastic container for the job, maybe the size of a beer jug, over which you can put the mesh/flyscreen lid of your enclosure. This will enable you to see if your insects are up to anything while you clean...

Flight

The males have large wings and are good at using them. They will fly if agitated, uncomfortable, or if they are falling for whatever reason. Using their ability to fly and their high movement speed, male E. tiaratum can be slippery customers when being moved from one enclosure to the next. It's probably a good idea to close any doors or windows, and turn off any fans when having fun with your male insects.

Still, its an impressive sight when one of these insects takes to the skies. Rather than the low buzzing sound that you might expect from a large insect in flight, these produce a flapping sound similar to that of a bird's wings.

Eating & Drinking

Feeding usually happens at nighttime, when the insects are more active. I say usually because being in captivity seems to alter their perception of time anyway. At any rate, Mrs. Miyagi often dives for the nearest food when startled...

Eating

The insects will eat by moving their heads in arcs along the edges of leaves, chewing as they go. Once an arc is completed, they go back to the start of the arc and eat the newly exposed leaf edge in the same manner. The sequence is reminiscent of a typewriter. All the while, the four appendages around their mandibles will be gripping the leaf. My best guess is that these serve to align the food and to detect it - while searching for food, the appendages will move about frenetically.

They will eat their way right into the middle of a leaf, and all the way to the other side, leaving a large portion of the leaf to fall to the ground, uneaten. Their huge appetite (especially when fully grown) is evidenced by the rate at which they can strip a small branch of all of its leaves, and the large quantity of droppings (each about the size of a mouse's, when the insects are fully grown) littering the floor of the enclosure.

Drinking

The insects appear to get much of their water from the moisture in the leaves they eat, however, they will drink the small droplets of water on the leaves and branches in the enclosure that remain after a misting. Most of this is ingested along with the leaves too, but I have seen footage of an E. tiaratum lapping up droplets off of a branch it was perched on. It was moving its head in a similar way to its eating pattern, minus the biting with its mandibles.

Important: During periods of hot weather, it is necessary to spray the insects and the enclosure with water as often as once every three hours. They do not cope well with a combination of low water, dry plants and incredibly high temperatures. Also ensure that the recepticle containing the foodplants is well stocked with water, as the plants can dry out surprisingly quickly, leaving the insects with an unappealing, crunchy meal.

Reproduction & Breeding

Sexual dimorphism

Mating behaviour

Egg laying

• Egg laying began a month after Mrs. Miyagi reached full maturity.

• The rate of laying started out slow, with about 4 eggs in the first week.
• After about another month, the rate had increased to at least 20 eggs per week.

• They seem to hold back on laying if there isn't a lot of food about.

• As of 06/03/2006, I Mrs. Miyagi has laid about 100 eggs.

• Egg colour/pattern varies - some are dark brown, whereas others are white with black patterns. I believe this is related to the diet of Mrs. Miyagi - the variation is between batches of eggs, corresponding roughly to the cycle of cage-cleaning. I've changed the plant type each time, sometimes alternating between two different types. The egg colour has gone from dark to white and back again...I wonder how this may impact the final colour of the insects that hatch.

• Some eggs find themselves in the water...hard to tell if they are going to be OK. These actually change colour - I've seen one go from almost black to white in my hand. I've noticed that two other 'water eggs' have become completely white...

• The eggs are laid with considerable force: she will flick them from her tail at high speed...you can hear them smacking against the sides of the enclosure and ricocheting off the glass of water. Sometimes this appears to be a defensive tactic - every now and then, when startled, Mrs. Miyagi will fire an egg! The point of this is probably just to save the egg from the parent's imminent demise, and most likely occurs only if an egg is ready for launch anyway.

Rearing the eggs

Nothing much to report here, other than none of the eggs have hatched. I have heard varying reports of the time required; these range from 9 months to 3 years, so there might be quite a wait. The worst thing is that I don't even know if they will hatch at all.

Care of hatchlings

Genetic diversity

Death

I was told that the expected lifespan of these insects is approximately one year for the males and 18 months for the females, from hatching to end. Given the age of the critters when they came into my life, my sensitivity to their needs, and the similar nature of their passing, I make the assumption that the deaths of Mr. and Mrs. Miyagi were typical.

A simple way of putting this is that the insect kind of slows to a stop over the course of several days. At first they may have trouble retaining grip on branches - they will often be found on the floor of their enclosure. Eventually they will be completely immobilised, perhaps with some signs of life. You may want to provide water in the hope that they recover, but by this stage such a thing appears unlikely.

Because of the drawn-out nature of this shutdown, it is difficult to assess when the insect is actually dead. All I can suggest is providing the necessities within easy reach of their mandibles; if they haven't moved at all for several days and/or fail to eat then the insect is, to all intents and purposes, dead.

I urge you to treat the body with respect. Conduct appropriate rites and whatever you do, don't mount the thing on a board. I suspect that the reason why biting insects leave me alone is because of the dignified manner in which I carried out the death-ceremonies of these insects.

Generation 1.5 - A & B

After about a year, I have gotten sick of waiting for the eggs to hatch, and so I have purchased two new insects. Same species as before, but quite a lot younger by the looks of things. As far as the names go, I had to select them from the huge number of responses from last Thursday's phone-in poll: the bigger one is named A, the smaller B. I am told they are both female, the bigger and older of the two is approx. 6cm long, the smaller is about 4cm long. They look just like miniature versions of the adults, without the wings or swollen abdomen. I will post a picture here soon.

I have retained about 10 of the Miyagi eggs in the hope they will hatch one day, carrying on the Miyagi name. Also this might bring some genetic diversity to the bug house.

25/04/2007

I think both are getting ready to moult. A has been hanging from the roof of the enclosure for the last two nights, not moving much at all (except when startled). In the last couple of hours, B has joined her there. This might prove to be another example of that weird synchronised moulting thing I described earlier.

28/04/2007

A moulted and is now almost twice as big as she was. Also, she has gone from a chocolate brown colour to orange.