Funnelweb Spider Bites and Venom
Created | Updated Jan 28, 2002
Australia is home to the world's most venomous spiders.
This article describes a little about the natural history of these spiders, why we encounter them when we do, why their venom is so dangerous to us, bite symptoms and basic first aid.
Funnelwebs and Mouse spiders are primitive spiders, or mygalomorphs. A distinguishing characteristic of mygalomorphs is that they have large jaws and fangs that are paraxial - that is, set parallel to each other. The fang action is therefore a stab, rather than a pinch, and larger animals are powerful enough to stab through a fingernail or even a wellington boot.
By nature mygalomorphs are shy and secretive, hiding deep in their burrows or retreats during the day. Females rarely leave their burrows and are seen only when flood, landscaping or building work disturbs them. Males on the other hand abandon their burrows when sexually mature, stop feeding and single-mindedly search for females. All mygalomorph males wander at night (only some Mouse spider males venture out in daylight). During the day the males find somewhere dark, cool and humid to rest.
Very few accidentally wander into houses; they cannot climb very well, but any house on a concrete plinth is accessible to them, and they usually make their way to the kitchen, bathroom or laundry.
Funnelweb spiders are found only in eastern and southern Australia (including Tasmania). Of the 35 - 40 species known, only one is known to be fatal to humans; nevertheless funnelwebs make up most of the world's deadliest top 30. The only rivals are the little-known Mouse spiders. These rare animals are seldom encountered; only one bite is known and thankfully that was not fatal.
The next most dangerous group of spiders are members of the Latrodectus genus, which includes the red-back and the American Black Widow spider.
Exactly which is the most venomous species depends on the criteria used; but it seems certain that both in terms of venom composition and the number of recorded fatalities this distinction belongs to the Sydney funnelweb, Atrax robustus.
Members of the genus Hadronyche, which includes all but three of the known funnelweb species, have never inflicted a fatal bite.
All spiders have a cocktail of toxins and digestive enzymes in their venom, whose function is to quickly immobilise and digest their prey.
Funnelwebs are dangerous to humans because one of the toxins they possess is a powerful neurotoxin. Marsupials and most mammals have natural blockers to these, but unfortunately primates do not. Funnelweb bites are therefore relatively harmless to native wildlife, livestock and pets (unless you have a pet chimpanzee!) but potentially fatal to humans.
Also, the mix of the venom cocktail is different in males and females, mature males having more of the neurotoxin.
The combination of large, powerful, stabbing fangs, male wandering habits, and high levels of neurotoxin in the male venom, is the reason why funnelweb bites are so notorious.
Having said all that, we should remember that spiders will only bite in self-defence, and only then under provocation. The rearing behaviour, where the animal raises itself to its full height, spreads its front legs and opens its jaws, is intended as a deterrent, and many spiders do this; I have seen a cornered huntsman do it. It is not an aggressive posture. Funnelwebs have their eight eyes in a group on top of their head, just behind the jaws, which means that when they rear they are unable to see what is in front of them.
However, the front legs have very long, very fine sensory hairs that detect air movement; breathe gently on a rearing funnelweb and it will strike blindly; very impressive!
The spider which bites is most likely to be the one you don't see, hidden in shoes, blankets, piles of washing. These are good hiding places for the wandering males, so keep them off the floor.
Treated with respect, and handled gently, spiders can be safely captured in a glass jar and released in the garden to go about their business; for every funnelweb that makes its way into your house, you can be sure there are many, many more wandering around outside.
If you are unlucky enough to be bitten, you will know it immediately. Do not panic! (funnelwebs do NOT generally make a tasty meal of visiting tourists...)
The majority of bites do NOT result in envenomation, although local pain at the site of the bite is common. Only the male Sydney funnelweb has ever caused death, and then only before the development of an antivenom. You should assume the worst, however, especially if the victim is a child.
First aid is straightforward:
- do NOT cut the wound or try to suck the venom out
- apply a pressure bandage straight away, as for snakebite; start above the site of the bite, work towards the end of the limb, then back
- immobilise the limb
- do NOT apply a tourniquet
- if you do not have a pressure bandage (and you really should have one in the house), improvise one with strips of cloth
- go straight to hospital; phone ahead if you can to make sure they are ready for you
- do NOT remove the pressure bandage, however well you may be feeling!
Symptoms can include tingling around the mouth; tongue spasms, watering eyes, abdominal pain, nausea, vomiting, muscle spasms and twitches, and difficulty breathing.
Most victims are kept in hospital for observation and released without treatment; antivenom is used in only about 10% of cases, and since its development there have been no deaths from funnelweb bite.
Many people ask me if I milk the spiders I collect; I'm afraid the answer is no! Luckily there is no need to maintain supplies of venom from each funnelweb species (unlike snakes) because the antivenom derived from the Sydney funnelweb has proven effective for all funnelweb and mouse spider bites.
The Australian Reptile Park collect and milk the venom from male Sydney funnelwebs. Milking is very easy; you just frighten the spider and he will rear, opening his fangs and exuding venom, which is sucked up into a glass pipette. The venom is then injected into rabbits (it doesn't kill them!); the rabbits immune system creates large numbers of immunoglobulin proteins, which are then extracted and purified to give antivenom.
This article describes a little about the natural history of these spiders, why we encounter them when we do, why their venom is so dangerous to us, bite symptoms and basic first aid.
Funnelwebs and Mouse spiders are primitive spiders, or mygalomorphs. A distinguishing characteristic of mygalomorphs is that they have large jaws and fangs that are paraxial - that is, set parallel to each other. The fang action is therefore a stab, rather than a pinch, and larger animals are powerful enough to stab through a fingernail or even a wellington boot.
By nature mygalomorphs are shy and secretive, hiding deep in their burrows or retreats during the day. Females rarely leave their burrows and are seen only when flood, landscaping or building work disturbs them. Males on the other hand abandon their burrows when sexually mature, stop feeding and single-mindedly search for females. All mygalomorph males wander at night (only some Mouse spider males venture out in daylight). During the day the males find somewhere dark, cool and humid to rest.
Very few accidentally wander into houses; they cannot climb very well, but any house on a concrete plinth is accessible to them, and they usually make their way to the kitchen, bathroom or laundry.
Funnelweb spiders are found only in eastern and southern Australia (including Tasmania). Of the 35 - 40 species known, only one is known to be fatal to humans; nevertheless funnelwebs make up most of the world's deadliest top 30. The only rivals are the little-known Mouse spiders. These rare animals are seldom encountered; only one bite is known and thankfully that was not fatal.
The next most dangerous group of spiders are members of the Latrodectus genus, which includes the red-back and the American Black Widow spider.
Exactly which is the most venomous species depends on the criteria used; but it seems certain that both in terms of venom composition and the number of recorded fatalities this distinction belongs to the Sydney funnelweb, Atrax robustus.
Members of the genus Hadronyche, which includes all but three of the known funnelweb species, have never inflicted a fatal bite.
All spiders have a cocktail of toxins and digestive enzymes in their venom, whose function is to quickly immobilise and digest their prey.
Funnelwebs are dangerous to humans because one of the toxins they possess is a powerful neurotoxin. Marsupials and most mammals have natural blockers to these, but unfortunately primates do not. Funnelweb bites are therefore relatively harmless to native wildlife, livestock and pets (unless you have a pet chimpanzee!) but potentially fatal to humans.
Also, the mix of the venom cocktail is different in males and females, mature males having more of the neurotoxin.
The combination of large, powerful, stabbing fangs, male wandering habits, and high levels of neurotoxin in the male venom, is the reason why funnelweb bites are so notorious.
Having said all that, we should remember that spiders will only bite in self-defence, and only then under provocation. The rearing behaviour, where the animal raises itself to its full height, spreads its front legs and opens its jaws, is intended as a deterrent, and many spiders do this; I have seen a cornered huntsman do it. It is not an aggressive posture. Funnelwebs have their eight eyes in a group on top of their head, just behind the jaws, which means that when they rear they are unable to see what is in front of them.
However, the front legs have very long, very fine sensory hairs that detect air movement; breathe gently on a rearing funnelweb and it will strike blindly; very impressive!
The spider which bites is most likely to be the one you don't see, hidden in shoes, blankets, piles of washing. These are good hiding places for the wandering males, so keep them off the floor.
Treated with respect, and handled gently, spiders can be safely captured in a glass jar and released in the garden to go about their business; for every funnelweb that makes its way into your house, you can be sure there are many, many more wandering around outside.
If you are unlucky enough to be bitten, you will know it immediately. Do not panic! (funnelwebs do NOT generally make a tasty meal of visiting tourists...)
The majority of bites do NOT result in envenomation, although local pain at the site of the bite is common. Only the male Sydney funnelweb has ever caused death, and then only before the development of an antivenom. You should assume the worst, however, especially if the victim is a child.
First aid is straightforward:
- do NOT cut the wound or try to suck the venom out
- apply a pressure bandage straight away, as for snakebite; start above the site of the bite, work towards the end of the limb, then back
- immobilise the limb
- do NOT apply a tourniquet
- if you do not have a pressure bandage (and you really should have one in the house), improvise one with strips of cloth
- go straight to hospital; phone ahead if you can to make sure they are ready for you
- do NOT remove the pressure bandage, however well you may be feeling!
Symptoms can include tingling around the mouth; tongue spasms, watering eyes, abdominal pain, nausea, vomiting, muscle spasms and twitches, and difficulty breathing.
Most victims are kept in hospital for observation and released without treatment; antivenom is used in only about 10% of cases, and since its development there have been no deaths from funnelweb bite.
Many people ask me if I milk the spiders I collect; I'm afraid the answer is no! Luckily there is no need to maintain supplies of venom from each funnelweb species (unlike snakes) because the antivenom derived from the Sydney funnelweb has proven effective for all funnelweb and mouse spider bites.
The Australian Reptile Park collect and milk the venom from male Sydney funnelwebs. Milking is very easy; you just frighten the spider and he will rear, opening his fangs and exuding venom, which is sucked up into a glass pipette. The venom is then injected into rabbits (it doesn't kill them!); the rabbits immune system creates large numbers of immunoglobulin proteins, which are then extracted and purified to give antivenom.
