Lizzy Lowe, Macquarie UniversityStunning photographs of vast, ghostly spider webs blanketing the flood-affected region of Gippsland in Victoria have gone viral online, prompting many to muse on the wonder of nature.
But what’s going on here? Why do spiders do this after floods and does it happen everywhere?
The answer is: these webs have nothing to do with spiders trying to catch food. Spiders often use silk to move around and in this case are using long strands of web to escape from waterlogged soil.
This may seem unusual, but these are just native animals doing their thing. It’s crucial you don’t get out the insecticide and spray them. These spiders do important work managing pests, so by killing them off you would be increasing the risk that pests such as cockroaches and mosquitoes will get out of control.
What you’re seeing online, or in person if you live locally, is an amazing natural phenomena but it’s not really very complicated.
We are constantly surrounded by spiders, but we don’t usually see them. They are hiding in the leaf litter and in the soil.
When these flood events happen, they need evacuate quickly up out of holes they live in underground. They come out en masse and use their silk to help them do that.
You’ll often see juvenile spiders let out a long strand of silk which is caught by the wind and lifted up. The web catches onto another object such as a tree and allows the spider to climb up.
That’s how baby spiders (spiderlings!) disperse when they emerge from their egg sacs — it’s called ballooning. They have to disperse as quickly as possible because they are highly cannibalistic so they need to move away from each other swiftly and find their own sites to hunt or build their webs.
That said, I doubt these webs are from baby spiders. It is more likely to be a huge number of adult spiders, of all different types, sizes and species. They’re all just trying to escape the flood waters. These are definitely spiders you don’t usually see above ground so they are out of their comfort zone, too.
This mass evacuation of spiders, and associated blankets of silk, is not a localised thing. It is seen in other parts of Australia and around the world after flooding.
It just goes to show how versatile spider silk can be. It’s not just used for catching food, it’s also used for locomotion and is even used by some spiders to lay a trail so they don’t get lost.
Don’t spray them!
The most important thing I need readers to know is that this is not anything to be worried about. The worst thing you could do is get out the insecticide and spray them.
These spiders are making a huge contribution to pest control and you would have major pest problems if you get rid of all the spiders. The spiders will disperse on their own very quickly. In general, spiders don’t like being in close proximity to each other (or humans!) and they want to get back to their homes underground.
If you live in Gippsland, you probably don’t even need to clear the webs away with a broom. There’s no danger in doing so if you wish, but I am almost certain these webs will disperse on their own within days.
Until then, enjoy this natural spectacle. I wish I could come down to see them with my own eyes!
Humans aren’t the only ones in trouble. Many of the animals that live with and around us are also heading for higher ground as the floodwaters rise.
Often small creatures — especially invertebrates like spiders, cockroaches and millipedes — will seek refuge in the relatively dry and safe environments of people’s houses. While this can be a problem for the human inhabitants of the house, it’s important to make sure we don’t add to the ecological impact of the flood with an overzealous response to these uninvited guests.
What floods do to ecosystems
Floods can have a huge impact on ecosystems, triggering landslides, increasing erosion, and introducing pollutants and soil into waterways. One immediate effect is to force burrowing animals out of their homes, as they retreat to safer and drier locations. Insects and other invertebrates living in grass or leaf litter around our homes are also displaced.
Even species that don’t thrive after floods are likely to become more visible as they flock to our houses for refuge. But an apparent short-term increase in numbers may conceal a longer story of decline.
After periods of flooding, the abundance of invertebrates can fall by more than 90% and the number of different species in an area significantly drops. This has important implications for the recovery of an ecosystem, as many of the ground dwelling invertebrates displaced by floods are needed for soil cycling and decomposition.
So before you reach for the bug spray, consider the important role these animals play in our ecosystem.
What to do with the extra house guests?
If your house has been flooded, uninvited creatures taking shelter in your house are probably one of the smaller issues you are facing.
Once the rain subsides, cleaning in and around your property will help reduce unwanted visitors. Inside your house, you may see an increase in cockroaches, which flourish in humid environments. Ventilating the house to dry out any wet surfaces can help get rid of cockroach infestations, and filling crevices can also deter unwanted visitors.
In the garden, you may see an increase in flies in the coming weeks and months as they lay eggs in rotting plants. Consider removing any fruit and vegetables in the garden that may rot.
Mosquitoes are also one to watch as they lay eggs in standing water. Some species pose a risk of diseases such as Ross River virus. To prevent unwanted mozzies, make sure to empty things that have filled with rainwater, such as buckets and birdbaths.
If you do encounter one of our more dangerous animals in your home, such as venomous snakes and spiders, do not handle them yourself. If you find an injured or distressed snake, or are concerned about snakes in your house, call your local wildlife group who will be able to relocate them for you.
Just like the floods, which will subside as the water moves on, the uninvited gathering of animals is a temporary event. Most visitors will quickly disperse back to more appropriate habitat when the weather dries, and their usual homes are available again.
Don’t sweat the small stuff
While many of the impacts of floods are our own making, through poor planning and development in flood-prone areas, effective design of cities and backyards can mitigate the risks of floods. Vegetation acts as a “sponge” for stormwater, and appropriate drainage allows water to flow through more effectively. Increasing backyard vegetation also provides extra habitat for important invertebrate species, including pollinators and decomposers.
With severe weather events on the rise, it is important to understand how ecosystems respond to, and recover from natural disasters. If invertebrates are unable to perform vital ecosystem functions, such as soil cycling, decomposition, and pollination, ecosystems may struggle to return to their pre-flood state. If the ecosystems don’t recover, we may see prolonged booms of nuisance pests such as mosquitoes.
A few temporary visitors are are a minor inconvenience in comparison to the impacts floods have on the environment, infrastructure and the health and well-being of people impacted. So while it may seem like a bit of a creepy inconvenience, maybe we should let our house guests stay until the flood waters go down.
Many insects and spiders have been growing over the winter months to emerge once the weather gets warmer. This means you’re probably going to start noticing more spiders around your house and garden. So which ones should you worry about?
Don’t fear these common household spiders
Some spiders like to live in houses. It’s cool, dry and there are hundreds of tasty insects to eat that you may not have even noticed, such as silverfish, book lice and springtails.
One of the most common spiders people find at home across Australia is, true to its name, the black house spider. These spiders build messy webs on fences and in the corners of windows.
Because they’re black, people can mistake these spiders for funnel-webs, but black house spiders are smaller and harmless. Also, a funnel-web will never make a web in your window.
However, Australia is home to a number of “medically significant” spiders whose bites can be severe.
Funnel-webs are emerging from their burrows
First and foremost are funnel-web spiders, which are in the Atracidae family. Sydneysiders are likely well aware of the infamous Sydney funnel-web spider (Atrax robustus), but there are actually around 40 species of funnel-web spiders spread up and down the east coast of Australia.
Most funnel-webs will spend their lives hidden in their burrow. But during spring and summer, male spiders will wander about the bush (and sometimes back gardens) looking for mates, increasing the risk of human contact.
Recent studies into funnel-web venom evolution have shown male Sydney funnel-webs have a high concentration of a toxin called “delta-hexatoxin”, which disrupts neuronal signalling and can lead to respiratory and cardiac failure. This helps them catch insect prey and defend themselves by causing pain in predators.
The hexatoxins are distributed throughout the funnel-web family. To date, serious bites have only been reported from funnel-webs in southern Queensland and NSW. This includes the Sydney, Blue Mountains, Toowoomba/Darling Downs and the Northern Tree-dwelling funnel-web spiders.
Fortunately, clinical studies suggest serious mouse spider bites are rare, but these spiders should still be treated with caution.
And then there’s the renowned Australian redback spider (Latrodectus hasselti), with its striking red stripe. These spiders are found across the continent.
Redback spiders are related to American black widows and have toxins called latrotoxins, which also disrupt neuronal signalling in their prey. (It’s the female redbacks you need to keep an eye out for.)
Redbacks have a painful bite and symptoms can persist for several days. Fortunately for both redbacks and funnel-webs, effective antivenom treatments are available. If bitten, it’s always best to seek medical attention.
It’s worth noting no one has died directly from a spider bite in Australia in more than 40 years since the introduction of antivenom. So while Australian spiders may have a fearsome reputation, it’s somewhat overblown.
What to do with spiders in your house and garden
The first thing you should ask yourself is, do I need to get rid of them at all?
If you come face to face with an unwanted spider in your house, we recommend using a container and piece of paper for a simple catch-and-release into the garden. If the webs are what bothers you — and we’ve all walked face-first through a web at some point — sweeping them away will usually be enough for the spider to move on.
Alternatively, you can leave the webs in the garden to catch other insects (think of them as functional, miniature artworks).
Redbacks have a habit of building their webs under, for example, the rims of pot plants and in outdoor furniture. This can be a problem, especially for small children.
So keeping your house and garden tidy, regularly sweeping and avoiding leaving junk lying around makes your garden less attractive for web-building.
It’s also good to avoid leaving shoes outside (or shaking them out) and checking your swimming pools for lost wandering spiders. This will help prevent accidental contact with funnel-webs during spring and summer.
If you really have to kill a redback, a quick squish with the shoe is far better than using pesticides, which have negative impacts on human health and the environment. This includes polluting streams, harming birds and bees, and leading to insecticide resistance in pests such as cockroaches and mosquitoes.
Spiders are a key part of Australia’s native ecosystems, including in cities. The harm we do to our own health and the environment by using excessive pesticides far outweighs the risk spiders pose to us.
If we can learn to live alongside these not-so-creepy crawlies, our houses and gardens will be better for it.
Funnel webs are considered one of Australia’s most fearsome spiders, but their ability to kill humans is by accident rather than design, our new research shows.
In findings published today, we reveal how the highly toxic and quick-acting venom of male funnel-web spiders is likely to have developed as a defence against predators.
When male funnel-web spiders are young, their venom is potent mainly to insects, which they eat. But once males start searching for a female mate, they must leave the safety of their burrows. That’s when their venom becomes potent to vertebrates such as reptiles and mammals – including humans.
So while humans can theoretically die from a funnel web bite, this is just an evolutionary coincidence – our research suggests the spiders aren’t specifically out to get us.
Why so deadly?
About 15% of all animals use venom for reasons such as to kill or immobilise prey, self-defence or to gain advantage over competitors, such as during breeding season. As an animal matures and its activities change, so too can its venom.
Australian funnel webs are among a small group of spiders whose venom can kill humans. However all 13 recorded deaths occurred before anti-venom was introduced in 1981.
Funnel web venom is lethal because it contains a type of neurotoxin called “delta-hexatoxin”. This toxin can kill humans by attacking the nervous system, keeping nerves “turned on” and firing over and over again. In severe cases the venom can cause muscles to go into spasm, blood pressure to drop dangerously, coma and organ failure, and ultimately death – sometimes within a few hours.
Scientists have long been puzzled by why these toxins are so deadly to humans, when we and other primates have never been funnel web prey or predator. Scientists were also perplexed as to why male funnel webs appeared to have much deadlier venom than females, and caused most human deaths.
However we did know most funnel web bites in humans occur during the spiders’ summer mating season, when the male spiders rarely feed. This suggested the venom played a defensive role.
We set out to solve this mystery, using molecular analysis of the venom. Although 35 species of Australian funnel-web spiders were officially recognised, only nine delta-hexatoxins from four species had previously been identified. Our analysis increased the number of known delta-hexatoxins to 22, from the venom of ten funnel-web species.
Having this extra data helped us paint a much clearer picture of the venom’s story. It all comes down to natural selection – the process where organisms best adapted to their environment survive and procreate. The genes responsible for this success are preserved and carry on to the next generations, driving the process of evolution
Our data revealed how natural selection triggered a change in the venom of adult male funnel webs. When males sexually mature, they leave the safety of their burrow and wander considerable distances to find a female. This puts male funnel web spiders in the path of vertebrate predators. These can include reptiles (such as lizards or geckos), marsupials (such as antechinus and dunnarts), mammals (such as rats) and birds.
When funnel-web spiders evolved millions of years ago, toxins in its venom mainly targeted their natural prey: insects such as cockroaches and flies. We examined the genetic sequences of all delta-hexatoxins in funnel web venom. We found over time, the venom of adult males evolved to be potent to vertebrate predators. Unluckily for humans, who are vertebrate animals, we copped it in the process.
Female funnel webs stay safely in their burrows and let the males come to them. So the venom of females is thought to remain potent only against insects their entire lives.
Now armed with a stronger understanding of how delta-hexatoxins evolved, we want to put that knowledge to use. The new genetic sequences we discovered will enable a better understanding of what funnel web spider venom does to the human body. This could be critical for improving existing anti-venoms, and for designing evidence-based treatment strategies for bite victims.
We’re not just looking at the venoms of sexually mature males. We’re also examining female funnel-web venom, hoping their insect-specific toxins will lead to new types of insecticides which are less harmful to non-target insects and the broader environment.
Funnel webs may be one of Australia’s most deadly spiders. But perhaps its some comfort to know their venom is not targeted against us, and the potential lethal effects are just a stroke of evolutionary bad luck.
This article is part of Flora, Fauna, Fire, a special project by The Conversation that tracks the recovery of Australia’s native plants and animals after last summer’s bushfire tragedy. Explore the project here and read more articles here.
I’m standing on a hill in Kangaroo Island’s Western River Wilderness Protection Area, looking over steep gullies and sweeping hillsides. As far as I can see, the landscape is burnt: bright patches of regrowth contrast with skeletal, blackened trunks. It’s stark, yet strangely beautiful.
It’s late May, five months after the catastrophic summer fires burned 90% of the park. I’m here to assess the damage to some of our tiniest Australians.
Much attention has been given to the plight of Kangaroo Island’s iconic birds and mammals – the Glossy Black Cockatoo and the Kangaroo Island Dunnart, for example. However, the invertebrates – spiders, insects and myriad other groups – have largely been overlooked. These groups contain some of Australia’s most threatened species.
Among the invertebrates listed by the federal government as a priority for intervention is an unassuming, brownish-black spider with squat legs and a body about the size of a A$2 coin. Its name: the Kangaroo Island Micro-trapdoor spider (Moggridgea rainbowi).
The trials it now faces offer an insight into the enormous challenges ahead for invertebrates – the tiny engines of Australia’s biodiversity – in the wake of last summer’s cataclysmic fires.
The Kangaroo Island Micro-trapdoor spider has an interesting history. It is the only member of its genus found in Australia, its closest relative being in Africa. Studies show it arrived here between 2 and 16 million years ago, likely rafting across the ocean on vegetation! A true voyager.
Kangaroo Island Micro-trapdoor spiders exist only on Kangaroo Island. They live in short, 6cm burrows, built neatly into creek banks. They are slow, calm spiders, spending most of their time in their burrow, determinedly holding the door shut with their fangs.
The females care for their young; I have opened a trapdoor to find 20 tiny spiders living together with their mother. When ready, the young disperse short distances to build burrows of their own, tiny versions of the adult’s.
Assessing the damage
My colleagues and I are in this conservation park today to locate patches of less fiercely burnt land in which to look for survivors. Sadly, all the known western populations of this enigmatic spider were destroyed. I am yet to find any survivors in the fire ground, but it is early days.
We will be out here for the next year or so, walking hundreds of kilometres of creek lines, searching for signs of life. There is a lot of land out there. Around 210,000 hectares was burnt, almost half of Kangaroo Island. I remain hopeful that some colonies have survived.
If we find some Kangaroo Island Micro-trapdoor spiders – what then?
Surviving the initial blaze is the first step in the struggle for survival. The post-fire environment has many threats – habitat loss, exposure to hungry predators, weeds. Today, I noticed areas where soil, loosened by fire, has washed into creeks, completely burying them.
If we find some surviving individuals, we’ll protect them by installing sediment control, removing weeds and monitoring them in future.
Why should we care?
Not everyone loves spiders. I get that. But the functions invertebrates perform are vital. Our ecosystem relies on them; humans rely on them. Yet collectively our understanding of invertebrates – their importance and their value – is dangerously low.
The Kangaroo Island Micro-trapdoor Spider plays its own role the ecosystem. It is a predator, but we don’t really know what it eats. It’s a food source for birds, mammals or reptiles, but we don’t know what eats it. So, why should we care?
Firstly, I firmly believe every species has its own intrinsic value; every extinction, although a natural part of life, is a loss.
Secondly, the ecosystem is so complicated we don’t know exactly how the loss of one species will impact its prey, the parasites that live on it or its predators. And when we’re facing multiple extinctions, these effects could be devastating.
The Kangaroo Island Micro-trapdoor spider, the Kangaroo Island Assassin Spider, the Green Carpenter Bee – we only know these species are threatened because scientists like me have spent years or decades studying them.
But the majority of Australia’s invertebrate species are yet to be discovered. Many will be similarly at risk, but we have no way of measuring the scale of risk or the repercussions. That’s a fact we should all find scary.
There is hope, though. It’s not yet over for these species. Work such as ours is a step towards understanding how worsening bushfires will affect these vital, but often forgotten, members of our ecosystem.
After I found my first peacock spider in the wild in 2016, I was hooked. Three years later, I was travelling across Australia on a month-long expedition to document and name new species of peacock spiders.
Peacock spiders are a unique group of tiny, colourful, dancing spiders native to Australia. They’re roughly between 2.5 and 6 millimetres, depending on the species. Adult male peacock spiders are usually colourful, while female and juvenile peacock spiders are usually dull brown or grey.
Like peacocks, the mature male peacock spiders display their vibrant colours in elegant courtship displays to impress females. They often elevate and wave their third pair of legs and lift their brilliantly coloured abdomens – like dancing.
Up until 2011, there were only seven known species of them. But since then, the rate of scientific discovery has skyrocketed with upwards of 80 species being discovered in the last decade.
Thanks to my trip across Australia and the help from citizen scientists, I’ve recently scientifically described and named seven more species from Western Australia, South Australia and Victoria. This brings the total number of peacock spider species known to science up to 86.
Spider hunting: a game of luck
Citizen scientists – other peacock spider enthusiasts – shared photographs and locations of potentially undocumented species with me. I pulled these together to create a list of places in Australia to visit.
I usually find spider hunting to be a relaxing pastime, but this trip was incredibly stressful (albeit amazing).
The thing about peacock spiders is they’re mainly active during spring, which is when they breed. Colourful adult males are difficult – if not impossible – to find at other times of year, as they usually die shortly after the mating season. This meant I had a very short window to find what I needed to, or I had to wait another year.
Even when they’re active, they can be difficult to come across unless weather conditions are ideal. Not too cold. Not too rainy. Not too hot. Not too sunny. Not too shady. Not too windy. As you can imagine, it’s largely a game of luck.
The wild west
I arrived in Perth, picked up my hire car and bought a foam mattress that fitted in the back of my car – my bed for half of the trip. I stocked up on tinned food, bread and water, and I headed north in search of these tiny eight-legged gems.
My first destination: Jurien Bay. I spent the whole day under the hot sun searching for a peculiar, scientifically unknown species that Western Australian photographer Su RamMohan had sent me photographs of. I was in the exact spot it had been photographed, but I just couldn’t find it!
The sun began to lower and I was using up precious time. I made what I now believe was the right decision and abandoned the Jurien Bay species for another time.
I spent days travelling between dramatic coastal landscapes, the rugged inland outback, and old, mysterious woodlands.
I hunted tirelessly with my eyes fixed on the ground searching for movement. In a massive change of luck from the beginning of my trip, it seemed conditions were (mostly) on my side.
With the much-appreciated help of some of my field companions from the University of Hamburg and volunteers from the public, a total of five new species were discovered and scientifically named from Western Australia.
The Little Desert
Two days after returning from Western Australia, I headed to the Little Desert National Park in Victoria on a Bush Blitz expedition, joined by several of my colleagues from Museums Victoria.
To my surprise, we found a massive diversity of them, including two species with a bigger range than we thought, and the discovery of another species unknown to science.
This is the first time two known species – Maratus robinsoni and Maratus vultus – had been found in Victoria. Previously, they had only been known to live in eastern New South Wales and southern Western Australia respectively.
Our findings suggest other known species may have much bigger geographic ranges than we previously thought, and may occur in a much larger variety of habitats.
And our discovery of the unknown species (Maratus inaquosus), along with another collected by another wildlife photographer Nick Volpe from South Australia (Maratus volpei) brought the tally of discoveries to seven.
What’s in a name?
Writing scientific descriptions, documenting, and naming species is a crucial part in conserving our wildlife.
With global extinction rates at an unprecedented high, species conservation is more important than ever. But the only way we can know if we’re losing species is to show and understand they exist in the first place.
Maratus azureus: “Deep blue” in Latin, referring to the colour of the male.
Maratus constellatus: “Starry” in Latin, referring to the markings on the male’s abdomen which look like a starry night sky.
Maratus inaquosus: “Dry” or “arid” in Latin, for the dry landscape in Little Desert National Park this species was found in.
Maratus laurenae: Named in honour of my partner, Lauren Marcianti, who has supported my research with enthusiasm over the past few years.
Maratus noggerup: Named after the location where this species was found: Noggerup, Western Australia.
Maratus suae: Named in honour of photographer Su RamMohan who discovered this species and provided useful information about their locations in Western Australia.
Maratus volpei: Named in honour of photographer Nick Volpe who discovered and collected specimens of this species to be examined in my paper.
These names allow us to communicate important information about these animals to other scientists, as well as to build legislation around them in the case there are risks to their conservation status.
I plan on visiting some more remote parts of Australia in hopes of finding more new peacock spider species. I strongly suspect there’s more work to be done, and more peacock spiders to discover.
Australia is famous for its supposedly scary spiders. While the sight of a spider may cause some people to shudder, they are a vital part of nature. Hostile reactions are harming conservation efforts – especially when people kill spiders unnecessarily.
A pathological fear of spiders, known as arachnophobia, is of course, a legitimate condition. But in reality, we have little to fear. Read on to find out why you should love, not loathe, our eight-legged arachnid friends.
1. Spiders haven’t killed anyone in Australia for 40 years
Only a few species have venom that can kill humans: some mouse spiders (Missulena species), Sydney Funnel-webs (Atrax species) and some of their close relatives. Antivenom for redbacks (Latrodectus hasseltii) was introduced in 1956, and for funnel-webs in 1980. However, redback venom is no longer considered life-threatening.
2. Spiders save us from the world’s deadliest animal
Spiders mostly eat insects, which helps control their populations. Their webs – especially big, intricate ones like our orb weavers’ – are particularly adept at catching small flying insects such as mosquitos. Worldwide, mosquito-borne viruses kill more humans than any other animal.
3. They can live to an impressive age
The world’s oldest recorded spider was a 43- year-old female trapdoor spider (Gaius villosus) that lived near Perth, Western Australia. Tragically a wasp sting, not old age, killed her.
The University of Queensland is using spider venom to develop non-addictive pain-killers. The venom rapidly immobilises prey by targeting its nervous system – an ability that can act as a painkiller in humans.
The venom from a Fraser Island funnel web contains a molecule that delays the effects of stroke on the brain. Researchers are investigating whether it could be administered by paramedics to protect a stroke victim on the way to hospital.
Funnel-web venom is also being used to create targeted pesticides which are harmless to birds and mammals.
6. They could compete at Little Athletics
The Australian huntsman (Family Sparassidae) can run 40 body lengths per second, about eight times faster than the fastest human runners.
Other spiders have great throwing skills. To catch moths, the bolas spider spins a thread with a sticky glob of silk on the end. The glob mimics the scent of a female moth. When a male moth comes to investigate, the spider throws the glob at the moth, catches it then reels it in.
7. Spiders want to be left alone
Spiders are not aggressive and will either try to run away from people, or defend themselves. Many are exceptional at hiding or camouflaging themselves, in the hope we don’t even see them.
Wrap-around spiders (Dolophones species) flatten themselves around branches to hide during the day, then come out to build webs at night.
The Western Australian shield-back trapdoor spiders (Idiosoma species) uses its unusually hard abdomen to “plug” its tunnel when a predator enters, creating an impenetrable shield.
Trapdoor spiders live in burrows with a silken lid that shuts tight, then gets covered in dirt or leaf litter.
8. Spiders have very unusual sex lives
It’s well known that some female spiders eat their partners during or after sex. But male Tasmanian cave spiders have evolved to avoid this fate. They use kinks in their legs to pin the female’s fangs apart while they mate, which can prevent her from killing him. These spiders are so fascinating, they are the subject of a documentary, Sixteen Legs
More generally, male spiders use their “hands” (called pedipalps), to transfer sperm into female spider “vaginas” (called epigynes).
It is important to remember that spiders and other invertebrates – animals without spines – make up 98% of animal species. They are vital to the functioning of ecosystems; without them, the remaining 2% of vertebrates, including humans, could not survive.
OK, OK. I care about spiders. Now what?
Spread the word to your friends and family that spiders should be cared for.
By all means, teach children that certain spiders require caution, and should be admired from a safe distance. But if your child has an irrational fear of spiders, address this as early as possible. Encourage positive interest in the spider world by exposing children to books and movies with spiders as the lead protagonists, such as Charlotte’s Web and Spiderman.
Curious Kids is a series for children. If you have a question you’d like an expert to answer, send it to email@example.com You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.
Can you find out why spiders need six eyes but we only need two? – Amos, age 3, Newcastle.
Hi, Amos. Thanks for your excellent question.
The first thing we should say is that while it’s true that some spiders have six eyes, most actually have eight.
The short answer to your question is that animals have evolved different eyes that best suit the lives they lead.
Humans have two eyes that face forward. Our eyes are very good at seeing colours and shapes. Having two big eyes in the front of our head means they can work together to guess how far away something is (we call this “judging distance”). That makes it easier for us to catch another animal so we can eat it.
Spiders are also hunters and they need eyes that help them find and catch their food. In fact, most spiders can’t see very well, and use touch and taste to explore the world. But the kind of eyes they have tells us something about the food they eat and the lives they live.
Spider eyes for spider lives
Jumping spiders are active hunters, like tiny lions chasing down their prey (bugs). They usually have eight eyes: two very large front eyes to get a clear, colour image and judge distance, and extra side eyes to detect when something is moving. Here’s a picture of an Australian jumping spider.
Some spiders make nets to catch their prey. These net-casting spiders also need to see clearly and judge distances. Some have developed huge, scary-looking black eyes that stare straight ahead, so they are nicknamed ogre spiders! These gigantic eyes help the spider to see a wide area and accurately throw down its spider web net to catch its prey. Here’s a picture of a net-casting spider.
Some spiders live in caves that are completely dark, where eyes are no use at all. They have to rely on other senses to find their food in the dark. To save energy making eyes, these spiders lost their eyes during evolution, so now some of them have no eyes at all. You can see a picture of a spider like that here.
So why did most spiders end up with so many eyes?
Both human and spider eyes are the result of slowly evolving to help us survive in our different environments. One reason our human eyes are different from spiders is because our bodies and brains are also built differently.
For example, spiders don’t have necks. So they can’t turn their heads to look at things like we can. Having extra eyes around their heads is one way that spiders see more of the world around them, helping them to quickly spot prey or a potential predator.
Human eyes and spider eyes also do different jobs. Our two eyes are very complex and are good at doing many jobs at once, while spiders have different sorts of eyes that do different jobs.
For example, the large central eyes of jumping spiders are best for seeing shapes, but the simple side eyes have the important job of watching out for predators.
So a two-eyed spider or even an eight-eyed human isn’t impossible. But the two eyes we have and the eight eyes most spiders have are perfectly suited to help each of us live our lives just the way they are.
These newly described spiders have been given the common name palisade trapdoor spiders because of the strange and unique burrows they construct. The entrance to the burrow projects out from the surrounding soil like a miniature turret.
Not only that, but each of the four new palisade trapdoor spider species constructs its own unique type of burrow.
One species, found in national parkland near Gympie and known scientifically as Euoplos crenatus, constructs a particularly elaborate burrow. The hinged door that covers the burrow entrance is adorned with several rounded lobes which project from the door’s circumference.
This marvel of natural architecture is constructed by the spider using silk and soil. No other spider species in the world constructs something similar.
This species was originally discovered by local naturalists Kelvin and Amelia Nielsen in 1999, who then guided researchers back to the discovery location in 2016 to collect specimens so the species could be formally named.
Another species, Euoplos thynnearum, constructs a burrow entrance with a thick lip within which the burrow door sits. It’s found in the Mary Cairncross Scenic Reserve, a 55-hectare patch of subtropical rainforest popular with visitors to the Sunshine Coast hinterland.
This species is named after Elizabeth, Mabel and Mary Thynne, who originally donated the reserve land to the local council in 1941 to honour their mother Mary Thynne (née Cairncross). Currently, this species is known to occur only within the reserve and in other rainforest patches in the immediate vicinity.
Short-range species at risk
Species that only only occur in a very small area, like these new palisade trapdoor spider species, are known as short-range endemic species.
Although scientists are naming new species at a faster rate than ever before, estimates of the total number of species on Earth still suggest that most animal species have not been formally named. With so much work still to do, some scientists have chosen to prioritise work on particular types of animals that are especially vulnerable to extinction.
In 2002, Mark Harvey, an arachnologist from the Western Australian Museum, proposed that scientists should prioritise the discovery and description of short-range endemic species.
He reasoned that the small ranges of these species make them inherently vulnerable to extinction, and that identifying, naming and studying them is the first step to protecting them.
For trapdoor spiders, short-range endemism is the rule, not the exception. These spiders live their entire lives in a burrow. Juvenile spiders walk only short distances from their mother’s burrow, before constructing a burrow of their own.
Usually, these spiders will then remain in the same burrow for the remainder of their lives, enlarging it as they grow.
Adult male trapdoor spiders will also leave their burrow to breed, but will only travel relatively short distances. Over time, this extremely limited dispersal ability has led to the evolution of many different trapdoor spider species, each of which occurs in only a very small area.
Since 2012, a research team, led by Queensland Museum researcher Michael Rix, has been trying to discover and name all species of spiny trapdoor spider – this group includes the palisade trapdoor spiders, as well as other strange trapdoor spider species such as the shield-backed trapdoor spiders of Western Australia.
So far, this project has led to the description of more than 100 new species from throughout Australia, some of which are already classified as threatened by federal and state governments.
The discovery of all these weird and wonderful spider species should remind us that Australia has some of the most remarkable invertebrate species in the world, and new species are waiting to be discovered in the national parks and reserves which occur around, and even within, our towns and cities – under our noses.
Next time you visit a national park, or drive past a patch of forest while commuting along Australia’s east coast, think to yourself, what might be living in there? Do those species occur anywhere else? And above all, if we lose that forest remnant, what unique species might disappear along with it?