Canterbury Museum science communicator Morgane Merien takes you inside the hidden world of stick insects. Discover how these extraordinary creatures hide from predators and defend themselves.
So K uh my name is Moran Maran I did uh a lot of my postgrad studies on Stick INX so I did my honors and my PhD looking at New Zealand stick ins sex I was mostly interested in their camouflage and their color trying to understand basically do stick and seex
Actually look like sticks which may sound like a weird question because it’s so obvious to us yeah they do look like sticks but I was trying to understand what did they actually look like in a predator’s Vision because their predators animals like birds and um other insects and mammals have vastly
Different Visions than us humans so that’s what I was trying to understand um but in this talk I will be talking to you just about stick and sex in general from all around the world um trying to explain different parts of their life cycles and some of their defenses and
Then at the very end kind of talking about New Zealand stick insects and explaining why maybe they look a bit different than the ones overseas so stick and leaf insects um they are insects so like other insects they’ve got a head or thorax and abdomen
As well as three pairs of legs um they belong to the order fasma toia and fasma comes from the Greek for Phantom or ghost which is uh in regards to their obvious ability to disappear from people’s view there are around 300 Genera around the world with around 3,000 species
There’s always species that are continuously being discovered and described there’s quite a few that people know about they know where they’re located but they’ve just actually have not been described at all um all stick and leaf insects are herbivorous so they just eat plants that’s all they do they are mostly
Nocturnal so they will hang around during the day and kind of pretend to be what they’re pretending to be and then at night that’s when they go and find their friends and mate um so they’ve got small compound eyes and mulate Marth part mulate just means that um it’s kind
Of it can move like this they sometimes have wings sometimes those are functional and sometimes it’s only on one of the sex so sometimes the males will have the wings that they use to get to the females sometimes they still still do have wings but they are
Vestigial so they’re just kind of tiny little things that are left and they have other functions and they are quite well known for their very elongated legs so those are kind of the characters that make up the group of fids the fasia um they were once considered to be
Closely related to the orop which are the Crickets the weather the things like that but they are now considered um their own their own group um the one thing that’s important to note is that they kind of stand out as one of the groups that don’t really have very good phog
Gentics compared to other insect groups so it’s not been very well studied search certain stick andake groups subgroups in certain countries are a bit more studyed than others like in New Zealand but in other places it’s just not very well known at all so these are kind of the two shapes
That you’ll usually kind of see and that’s how sometimes people will separate them so you’ve got the leaf insects and then the stick insects obviously the leaf insects look like leaves the stick insects are shaped like a stick um they are still both fmia but that is one of the key
Sometimes differences between the two um so that’s a gray leaf insects from the SE shells and that is a cyclone Larry stick insect from North Queensland called Cyclone Larry because it was discovered only in 2006 when Cyclone Larry came through and knocked them down from the canopy of trees and they
Discovered them for the first time so 2006 um first Mia they can be found all over the world so except for Antarctic and kind of the north north north Patagonia type areas they’re quite numerous in the tropics and subtropics um but they are also found in temperate areas um and the greatest
Diversity is around that middle bit with the most known species are in Borneo which is where that star is they’ve got over 300 species on just their one Island uh making it the richest place to find stick insects in the world their life cycle so stick insects have a hemimetabolous life cycle that
Means uh incomplete metamorphosis so when they’ve got three stages you’ve got the eggs the nym stages the insta and then the adult so when the eggs hatch out and The Offspring comes out they look like mini versions of the adults compared to uh an insect like a butterfly who goes through
A complete metamorphosis so they do a complete change the the lvi looks completely different from the adult the stick insects have they just look like mini versions um just without the wings or um genitalia um and so to get to adulthood they have to go through a few malts so
This is when you shed your skin and then you grow you stretch and you’ve got to go through multiple of those to get to your final adult size so in that photo that’s the exact same species that’s just a baby newly hatched out and that’s the mum which is a lot lot
Bigger um and their lifespan it can range depending on the species but it can be a few months to sometimes 3 years and often times the environment the the climate can have quite an impact on that so in in hotter places they may be able to live for longer
Um and breed all year round uh in in places that are a bit more temperate the eggs are laid at the end of summer um beginning of Autumn and the eggs will overwinter so they’ll just kind of stay dormant and stay in the leaflet litter and they’ll overwinter
And then they’ll hatch back out hatch out when the temperatures come back up and the cycle continues so this is what a malt looks like so you can see that what’s hanging from that is the the skin the the white bit that’s what it’s moled out of um
They come out through the back so like a seam on the back and they uh all the limbs it’s like it’s like taking off you know a jumpsuit or something like that um and yeah so they’ve got to go through multiples of those uh and then sometimes they’ll often eat their own
Mals because you know waste not want not so so reproduction um there’s a few types of reproduction in stick insects there is sexual reproduction which is the one that most people are familiar with you know male female mix Offspring and then you also have asexual reproduction where there are certain species and certain
Populations where there’s only females there’s no males at all the females reproduce asexually so they just lay eggs that are unfertilized uh and the offsprings are clones of the mothers uh this is called parthenogenesis and it’s actually quite common in a few animals so if you ever
Hear about a virgin birth in a zoo from a shark or a snake or Li liard that’s pathogenesis that’s just a sexual reproduction um and pathogenesis can be obligate which means that they have to go through that reproduction mode that’s the only mode they can go through
There’s only females or it can be facultative in that instance there are males present in the population but the females are able to go between the two modes of reproduction they can choose so they can either decide to go and mate with a male or if there’s no males
Around or if they can’t be bothered they’ll go their own route um this is what I used um this this um mechanism is what was the basis of my honors project where I was looking at the cost of sex because although sex is beneficial in mixing genes and making
Sure that um organisms are quite um uh what’s the word strong against any changes that might happen it can be costly for the females because they often males can injure the females or they miss out on resources like food and things like that so that was the basis of my honors
Project and that’s how I kind of got started in the stick insect world and here I am six years later so the eggs of stick insects are really really interesting um they are incredibly species specific that means that the eggs all look different and are specific to to their species um so much
So that often times the eggs are the only way to tell between two different species are closely related um they look the the adults look very similar but you can only tell that they’re different species when looking at the eggs um not only that but the eggs themselves often
Their shape the way that they look reflects the way that they are being laid by the females uh so you’ll see that some of them kind of have spines along it that often means that it’s uh wind dispersed or it will um hook onto the fur of
Animals and get dispersed that way other ones are really uh thin and long because they get stuck into leaves and things like that so I will show you those so here’s OS so oi position is the way that eggs are laid so in fmia in stick and leaf insects we recognize five
Different ways of os the most basic one is to drop the eggs or flick them um I’ll just throw them away um that’s kind of recognized as the the Primitive or the ancestral character state so that’s what the ancestor would have had and then over time The Descendants have evolved their
Own mechanisms based on certain requirements of their environment so the other one is to bury or insert eggs into soil and crevices oft times that’s done so that you know the eggs are hidden away from predators or from parasitti um like like was and things like that
Another one is to glue the eggs to substrate like a leaf or bark or Branch another one is to pierce the eggs into leaves and then the fifth one is to produce an uika uika is just an egg Mass so that’s what this one is it’s an egg
Mass they’re all stuck together into their own little thing um like pray meeds do that they they lay an egg case um and actually uh eggs often get predated on by a lot of different things because they just you know are in the leaf litter and they’re in there for quite a
While so they can get eaten by other insects and they can sometimes uh go moldy from fungi and things like that or get parasitized by wasp um but there’s research that’s been done Japanese research that’s been shown that even when stick insects get ingested by birds they sometimes Will Survive the gut
Track of the bird get poed out and still hatch out so not All Is Lost um and here is an example of a this is a Malaysian Moss mimic stick and Z as you can see it’s quite beautiful and right now it’s trying to insert its eggs into
The the bark into the Moss so the end of its abdomen right there that’s been stuck in um it’s kind of like a knife or a fork and it’s sticking it in and leaving the egg behind there we go so mercori is a different type of um it’s ant mediated egg
Disposal so many species eggs have a fatty knob like capitulum um at the the top of the egg so like right here and that mimics actual plant seeds so plant seeds will often have a yummy resource that’s there to attract the ants the ants will take
That back to their nest and they’ll only feed on the the fatty resource that’s there and the seeds are safe and can hatch out stick insects have decided that’s a really great mechanism let’s copy it so some stick insects have evolved that their eggs also have that
Fatty knob at the top of their eggs and so that um their eggs can get dragged into the N estest the ant’s Nest uh and be safe from predators and then what happens is the eggs hatch out and The Offspring the stick insects like that one right there um they look like the
Ends themselves um and and they can just you know they can fool the ants and just walk out of the nest and go on about their lives and just go straight to the canopy and be completely okay um which is quite amazing and you know a great
Form of mutualism because the ants just get fooled but at the same time they do get a resource out of it for their own you know nest and offsprings and so on uh so that’s an mediated egg dispersal so sexual dimorphism sexual dimorphism is when there is a
Difference between the Sexes between the males and the females sometimes the males are bigger than the femal sometimes the females are bigger than the males in fmia It’s usually the female that is a lot bigger than the male uh and that’s usually because she just needs a larger body to store
Resources to create eggs um and and to to be able to just eat enough and so mating peers are quite common and you’ll see the male so that small one brown there that’s a male don’t that’s the same species they can look quite different which can often fool scientists into thinking they’re
Completely different and then they’ll see them mating in the wall and be like ah you two go together of course um so that’s the male on top and what they do is they mount the female and they’ve got claspers at the end of their abdomen abdomen their genitalia kind of like low
Hooks and they’ll go under the abdomen of the female and they’ll they’ll hook on and be able to mate and usually this mating population can last between a few hours to a few days so the males will usually hang on top of the female for quite a while not all the time actually
Mating but just hanging on and it’s a form of M guarding it means that um they’re stopping the females from having any access to any other males and making sure that their population is the one that gets uh goes to the end um obviously it can be
Quite uh annoying I’m not going to anthropomorphize it but for the females obviously she now has this weight on her back uh she it means that they’re a much larger Target for Predators like birds um but it also means that the male usually you know he can’t really get
Much of the food and eat so he just can only go where she’s going and get what she gets H and so on that side that that mating pair down there that is one of our stick insects in New Zealand this is from um Malaysia jungle
Nymph so the longest insect in the world is a stick insect we can claim that one um it is currently an undescribed species from China and formerly referred to as fanista kenis in the wild the female that was found measured 62.4 CM so it’s about the
Length of my arm um and then they kept her and reared some of her eggs and one of her Offspring actually ended up being even longer than her and made it to 64 CM uh which is quite amazing so at this point I think it’s a branch
Insect um but we can’t talk about so that’s the longest insect in the world we don’t have the smallest insect in the world but here’s the smallest stick insect uh which are the males of this species tyina Christina the one down there they’re about 2 cm they’re
From USA here’s a sister species Tamina c calicum um and so those are quite small and quite cute and these stick insects Hina are a very ancestral very old species of stick insects um they form their own group separate from the rest of the stick insects so let’s look at anti-predator
Defenses so stick insects are quite vulnerable to Predators due to their large size they make a very good meal um they’re often quite slow and often even if they do have wings they don’t fly that well uh so theyve evolved quite a few defenses to get away from predators
Or deter them or just tell them to back off so one of them is spikes and armor plates and just you know saying that oh I’m not going to be a good mouthful for you it’s not going to be fun um so this is one of artick insects here in New
Zealand this is Akin fuk Island PR the SP spiky spiny stick insect and then that one down there is a stick insect from Borneo called a touch me not stick insect which is fairly obvious as to why it’s called that another defense are chemical secretions um so those are when stick
Andx when they get sufficiently provoked they can release a noxious fluid from uh glands that are on their forax or behind their head um so for example this is the southern two strip walking stick from North America and they release a really strong fluid that um can cause tempor
Temporary blindness so would not recommend getting that in your eyes um and that is a peppermint stick insect peppermint because the fluid smells like pepper M and here it is in action yeah you really get dowed another chemical defense are uh um antipredator defense is called startle
Displays or datic displays um and those those uh are meant to kind of startle predators that are getting a bit too close by usually flashing really bright colors um and also making quite a loud noise so uh this one the black beauty stick insect from Peru uh has got these
Little tiny vestigial Red Wings which are not they can’t use them to fly but they will uh when they’re lying flat on the body you can’t tell that they’re there but then they’ll be able to flash them out really quick and kind of it’s
Kind of like big red flags like no no no no don’t get any closer uh they do also these Beauties spray chemicals as well so they’ve got two defenses um this is another stick insect that also has got those bright wings uh as well as spikes
And things like that so it can be quite you know startling another kind of startle display which is a little bit more on the the mimicry side of it is that some species have been observed to curl their abdomen upwards over their body um to resemble ants or scorpions
And kind of make the Predators think that they are something different than they are uh and allows them to avoid being eaten so this is a sub adult female uh in a defensive posture and she’s kind of turned around and protect ended that her abdomen Cur is like a
Striking head of a or the tail of a scorpion uh another defense is called otomy uh which is also known as appendage shedding or self-amputation uh just like lizards stick insects are able to kind of let go of legs as a defense mechanism if something were to grasp
Them by leg they can just let it go and keep moving away and um with with insects they’ve got six legs obviously so missing one is usually not a big deal um they can also let go of those legs when they go through a shed or a malt
And it doesn’t go right uh if a leg gets stuck they’ll just let it go and leave it and what happens is that actually if there’re is sub if they’re not an adult yet and they’ve still got a few molds to go through they can grow back these legs
So that’s what’s happening to this nymph those two front legs that look a bit twisty those are just the two front legs growing back so over the next successive malts they’ll just get longer and longer but that’s why in the wild if you ever find a stick insect that’s kind of got
One leg shorter than the other that’s what’s happened they would have lost the leg at some point they’ve been growing it back and then when they get to an adult that’s it another cool defense is called phosis also known as playing dead usually in this so that’s very much
A live stick and sect I’ve got videos on my phone where you know I’ve got them on my hand I Pro I can do that with them as well you put them on their back and they just go katonic they just like oh I’m dead and uh the idea is that if they
Play dead the Predator will think oo this this one’s not good something’s wrong with it it’s probably gone bad or I don’t want to eat that um and they also kind of do that when they’re up in the trees and branches and you go to catch them they’ll kind of see
You coming and they’ll just let go and they’ll fall to the forest floor and just play dead there and you know if they fall among grasses or things like that it’s almost impossible to find them again so one advice if you go to try and catch a stick insect have a hand
Underneath ready and the other one at the top and uh that usually works out quite well the other kind of big defense antipredator mechanism that they have that most people know about is obviously camouflage so that’s kind of all the strategies that are involved in concealment uh and that kind of includes
Prevention of detection and recognition uh and here I’ve kind of separated them into two different ones because you have background matching which is when your overall appearance matches in terms of the color and the pattern of whatever background that you’re on and in this instance your Predator doesn’t actually even recognize
That there’s anything there they just kind of go over you and don’t see anything in masquerade it’s a slightly different strategy because in this instance you’re actually mimicking an object you’re looking like a stone or a bird poo or a stick and you’re mimicking an object that’s quite common in your
Environment and in this strategy the Predator does see you but they misclassify you as something completely innocuous something that it’s just a stick there’s hundreds of them I don’t need any of those Sor so obviously this is the one here yeah and then here looking like a branch that’s
Coming off the other Branch yeah yeah I promise you she there there’s another one here big green one um yeah these are both from New Zealand um and this was kind of the work that I did for my PhD trying to untangle what kind of strategy are they using
Because some animals will favor one strategy over another in the case of the stick insect what I found was that they seem to be combining mult strategies as once they’re they’re matching their color to their environment but it’s also about the shape of their body making them look like a stick along with
Behavior so making sure that they hang at an angle that makes them look like they’re a branch coming off the main branch so they’re kind of the ultimate camouflage experts um in some other species overseas you’ll get camouflage that’s quite incredible and extreme um so here is a moss stick
Insect so you would never be able to see this in the forest there is just you’ve got to be very patient I’ve often gone out with people that have wanted to come and do field work with me to look for stick insects and over the years I’ve kind of honed in
My my site and I’m used to it but people that are not used to it they’ll just they get very angry with me so especially when they tell me Moran I can’t see one I’ll come next to them be like there’s one right there ah
What and then kind of the very last one which is actually not that common but if you don’t want to stay hidden the other end of that spectrum is to be quite bright colored and to stand out um very much like the bright red wings although those can be hidden aposematism is
Warning coloration that’s there all the time that’s a strong clear warning do not eat me I will not be good for you sometimes in the same species you’ll have both strategies where this is the male that you can see hanging onto the female so the male is really brightly
Colored like really brightly colored um a crazy mix of red blues and yellows and then the big female she’s completely drab and brown and just staying hidden uh this isn’t undescribed species from new calonia which I quite like because it just looks like a striped zebra it’s quite cute so stick insects are
Worldwide um they usually sometimes they’re kept as pets and so those are really well known and quite well loved but there’s quite a few that are like I said not described and sometimes it’s some that kind of go uh under the under the radar like this thick insect called
The Lord how Island stick inct which was R rediscovered in 2011 people had thought that it had gone extinct because it only lives on that small tiny little pyramid of an island called Ball’s pyramid um a few hundred years or so before then rats had been accidentally introduced to that
Island and had thought to have completely wiped them out um and they somehow uh they went back in 2011 and managed to find a couple of mating peers still on there and so at that point they were one of just the lowest kind of populations of any stick insects in the
World and so they managed to establish a breeding program around it and they’ve now brought it back it is still critically endangered but it is doing better and it’s in quite a few zoos in Australia so so New Zealand stick and xx what have we got so some of these are examples of
What we’ve got around the country um and you’ll notice that most of them are quite uh drab in colors so they tend to be green or brown and you know Shades in between none of ours have wings uh and a few of our species are completely asexual so there’s no
Males so I’ll quickly go through this so this is kind of the philogyny that we’ve got the classification that we’ve got for them at the moment so we’ve got nine Genera so those are the Genera with 23 different described species however that is set to probably change in the future
Because there’s quite a few species that are undescribed and a few other ones that are um that need to be synonymized that are the same across a few of them uh we can identify all the different species based on the arrangement of body spines of body size the structure of the male and
Female uh genitalia and the morphology of the egg as I said before is really important so I’ll kind of go through I’ve chosen a couple that you are the most likely to encounter down here because there are some that are only found in certain parts of New Zealand
For example um spino tarus this group is only found in the north of the north island so you you want if you find one down here Something’s Happened same with aelia fasma um tiaki fasma is only found in the north as well but Nivea fasma is only found in the
South it has not been found north of uh ARA’s pass so so this is Akin fola which is the most common one throughout New Zealand it’s found from the very North to all the way down to Rak raka Stewart Island uh there’s currently eight or nine recognized species that is likely to be
Uh reduced right down but some people are working on this in this genus there’s only females so all of those species are completely asexual no males at all they just get on with it um this is Argos satus which is our largest stick insect in New Zealand it
Is found in Canterbury uh the females can reach about 15 cm in length so they’re quite they’re not bad um they are found throughout much of the north island and some parts of the South Island uh although there was two described species aratus Horus and aratus Spiner most scientists now think that they’re
Synonyms and they’re one and the same so arachas Horus which is the oldest one gets um that’s the one that gets Provence and uh as I said some populations only consist of females so in this uh species they’re paog gentic but they’re facultative so they can go between the too and some populations
Will just have just been females so Something’s Happened where maybe a female got dispersed and kind of established their own population something like that there’s still a lot of research that needs to be done on how you know these populations get established this is cly tus which is um
The other one that’s really really common sometimes called the smooth stick insect so cacus hookery that’s the one that you’ll find all over New Zealand um and these guys are paog gentic as well facultative so again you’ll find populations with both females and males sometimes with just females and the females can just
Reproduce themselves um within cacus there is two species that are really restricted Kus tiaki only found um cap ranga and in Kus Rak which is restricted to the POR Island and then this is tarus there are four recognized species in this one uh and these guys are mostly
Found on estelia epiphytes and rata in climbing rata in the forest um they’re quite small compared to the other three that I showed you these guys are about 5 cm in length um and they look very similar to one another however often times the only way to to difference between them is to
Look at the eggs because the eggs look very very different um all our stick insects in New Zealand are endemic so they’re only found here however we always think about other animals invading us but what about some of our stick insects invading other places so we’ve got three species of our
New Zealand stick insects that have naturalized uh in the southwest England of all places in Cornwall uh they’ve been over there for over a 100 years we think that uh they got over there when nurseries were really into australasian plants and would bring over plants from New Zealand
And Australia back to the back to England to sell to you know well to-do people because it was quite Posh to have very exotic plants in your garden uh and so somehow the stick and sex made it over there maybe as eggs maybe even as nymphs and adults on Plants very
Unsure we do have records of them showing up in nurseries in Truro from the early 1900s I think the earliest record is 1908 uh and then from that that that place they’ve now spread around there and kind of established and the locals loved them so those photos are ones that
I took when I went to England because I went for a conference and I thought well I’m here I might as well go look for my stick insects so I found them and it’s really weird to see them on plants that you’re not familiar with but your stick
Insects look like the ones that you’re familiar with and yeah the locals love them because Europe is quite the corporate in stick and sect species so they’re very happy with them now color polymorphism um in New Zealand all of our stick insect species tend to be green or brown often in the
Same species you’ll see kind of variation in those um and I get questions a lot about well why is that is there you know what dictates it not really sure what dictates it because when these stick and sacks hatch they all look the same but then as they go
Through their Mals they kind of change into their final adult color um the main theory is that color polymorphism helps defeating Predator search image so Predator search image is what predators use to quickly find the food that they’re looking for so if you think I’m
A human my main food is an apple I know I need to look for around object that’s usually red and so those are kind of the characteristics I can quickly scan the environment and pinpoint anything that fits within those variables however if suddenly your apples are both red and
Green you now have to look for double that so that’s where color polymorphism comes in it helps to kind of slow down Predator search image and give you a bit more time uh there’s still a lot of research kind of going on into this to kind of see how it works but
Yeah and yeah how it actually comes about not really sure it could be uh humidity might dictate it also the plants that they feed on the plants that they usually uh use a substrate uh temperature things like that Predators so New Zealand stick insects do have a range of predators
Historically uh their predators would have mainly been Birds hence why their main defense mechanisms in New Zealand is mostly camouflage they don’t have a lot of chemical secretions or things like that because those usually work against quite um tenacious predator like mammals like rats and things like that
As in with birds uh with their visual system which is what they used to hunt things like mammals use smell and use movement to hunt and so with birds if you just manage to hide away that will usually be enough to defeat them um so they do get eaten by a whole
Lot of birds that’s kind of the main use of stick insects is that they’re food for a lot of other things they don’t really defoliate any trees and not harmful in any way they don’t spread any diseases they just kind of hang out and be fun uh they are also kind of being
Quite hammered by invasive wasp at the moment like uh this wasp is not a common Wasp that’s a paper wasp I don’t know what it says common wasp um yes so uh they do also looking at the literature they do they are being eaten by things like rats and hedgehogs and
Possums and stes and the like because if you come across a stick and Sack that’s the size it’s just a good meal for you so still a lot of research that needs to be done on that and that is me thank you very much