Mouse spiders probably aren’t the best-known spider in Australia, but they’re one that’s worthy of some respect. Found predominantly throughout Australia (with at least one species also in Chile), they’re sometimes mistaken for Trapdoor Spiders or Funnel-webs, and sometimes encountered in suburban gardens, and are known to sometimes fall into swimming pools. Although the name certainly gives people pause for thought, in reality, they’re not actually a mouse eating spider (at least, not normally) – although they have been known to eat small lizards and frogs though, so it’s probably not out of the question.
So, how dangerous are Mouse Spiders? How wary do we need to be of them, and what should we do if bitten by one?
What does a Mouse Spider look like?
Mouse Spiders are one of Australia’s “big black spiders” – the species treated with the most caution by medical professionals. This is particularly because they look relatively similar to the Sydney Funnel-web Spider – the Guinness book record holder for the world’s most venomous spider.
The body of the mouse spider ranges in size from around 1cm to 3.5cm, meaning a large one can be the size of your palm. The female Mouse Spider is coloured entirely black and has quite a shiny appearance (despite being a reasonably hairy spider). The male Mouse Spider will generally also be shiny black on the legs and much of the body, but they can often sport brightly coloured patches on their abdomen and head. The “head” (actually called a cephalothorax as it’s joined to the thorax – they don’t really have a neck) is quite large and bulbous, and their chelicerae (the bit where the fang joins onto the body) are distinctively huge. When it comes to jaws, Mouse Spiders look like a spider that works out.
Is the red headed Mouse Spider a different species?
It’s more accurate to say that the red headed Mouse Spider (missulena occatoria) is one of many species of mouse spider – notable for its unusual colour scheme. At one point, experts thought the male red headed Mouse Spider was a distinct species to the female due to the physical differences between them, although scientists have now linked the two.
The red headed Mouse Spider is also one of the only species of Mouse Spider known to use ballooning. This is when their young travel great distances by letting out long lines of spider silk, which are then caught by the wind and carried away. This may be why they are one of the most widely distributed mouse spider species.
The males are one of the most recognisable Mouse Spiders, with a distinctive red patch on its head region. The abdomen is often bright blue, which, ironically enough, makes it one of the only spiders in the world to feature Spider-man’s distinctive colour scheme.
Where do you find Mouse Spiders?
Mouse Spiders are found throughout most of Australia, including most populated coastal regions. Mouse Spiders don’t build webs in the conventional sense. Instead, they tend to create underground burrows lined with silk, generally around 20cm to 50cm deep. The mouse spider hole – the entrance to their lair – typically features a hatch of woven silk. For this reason, the Mouse Spider is sometimes counted as a type of Trapdoor Spider. Unusually, a mouse spider burrow has two separate entrances, generally near each other and roughly at right angles.
The Mouse Spider is an ambush predator. Generally, they live off prey (typically insects) that venture near their burrows, leaping out to catch anything that gets near enough. However, they do also go hunting outside their burrows – generally at night.
In late summer through to early autumn, male Mouse Spiders often go wandering in search of females to mate with. This is generally when they encounter humans – and when they tend to wind up in people’s swimming pools.
The Mouse Spider’s underground burrows may be where they get their name – the burrow being a little like a mouse hole. Although there’s argument about it – some experts assert that the name comes from the size of the spider (similar to a mouse) or from early researchers having found dead mice in their burrows and assuming they were regular prey.
Are Mouse Spiders dangerous?
The bad news is that Mouse Spiders are quite venomous. Although they’ve never caused any deaths, they have a pretty nasty bite, and there is some evidence that their venom could be almost as dangerous as Funnel-web venom. As Funnel-webs are one of the only two Australian spiders to ever kill humans, that’s a cause for concern.
Fortunately, serious Mouse Spider bites are pretty rare. Firstly because the Mouse Spider isn’t particularly aggressive towards humans. Secondly, because they quite often “dry bite” – sinking their fangs into an enemy but not injecting venom.
Regardless of this, the current consensus among medical experts is that if you’re bitten by a Mouse Spider – or any large black Australian spider – you should treat it as though you’ve been bitten by a Funnel-web and seek medical help immediately. This is partly because Mouse Spider venom can be potentially dangerous. But more significantly, because Mouse Spiders often look pretty similar to Funnel-webs, and many people would struggle to tell the difference.
At this point, Australia has had no Funnel-web deaths since Funnel-web antivenom was introduced in 1980 – over 40 years ago. That’s a record the Australian medical community is quite keen to keep intact, so the prevailing wisdom is that any bite from a large black spider should be treated like a Funnel-web bite.
First aid for Mouse Spider bites
If you’re lucky or forward-thinking enough to have done proper first aid training, you’ll already have some grounding in how to treat bites from venomous creatures like spiders and snakes. This means corporate first-aid officers, teachers, and other first aid trained personnel are probably the ideal people to take the lead if someone’s been bitten by a Mouse Spider.
The first thing to do after a large black spider has bitten someone is to check the area is safe – the last thing you want while trying to help a spider bite victim is to get bitten yourself.
The second thing is to Call 000 immediately. This might seem extreme – and hopefully, when the ambulance officers arrive, they’ll soon be telling you that there’s no significant danger. But Funnel-web venom is incredibly fast-acting – in at least one case, Funnel-web venom has killed children in as little as 15 minutes. By the time the victim starts to feel ill, you might be already running low on time.
Apply pressure to the wound where possible. If there’s a decent medical kid handy, use a pressure bandage. Ensure the victim sits down and moves as little as possible. Try to keep them calm. All this serves to slow down the venom and buy time for medical assistance to arrive.
If possible, it’s worth capturing or killing the spider and passing it on to medical personnel (provided this can be done with no danger) as it can allow the spider to be identified. If this can’t be done safely, taking a photo of the spider from a safe distance – or at least taking careful note of its appearance – will help.
Fortunately for bite victims, Funnel-web antivenom has also been shown to be highly effective against Mouse Spider venom – so no matter what spider bit you, there’s help available.