Skip to main content

Deadly Spiders: Poisonous or Venomous?

Black Widow

Black Widow

Spiders are Venomous

Poisonous generally refers to something that can make you ill if you touch it or eat it. Some mushrooms are poisonous to eat. Some frogs are also poisonous if you eat them. And yes, I'm sure someone, somewhere has done it.

Venomous refers to something that produces and injects venom into another creature. Spiders, snakes, and wasps are venomous. I've even known some venomous people.

Despite the horror movies, spiders rarely attack humans. When they do it is usually done to protect an egg sac, when the spider has been startled, or because the spider feels cornered. Who can blame them? I do the same thing.

A spider is not an insect, but an arachnid. Insects have 6 legs, arachnids have 8. Other arachnids are scorpions, mites, and ticks. The sub-group which classifies spiders is araneae.

Which Spiders are the Deadliest?

This depends on which expert you ask. Each has his own opinion and is happy to share it. Most experts do agree the Sydney funnel web spider, the "widow" types, the Australian redback, the widow family and the Brazilian wandering spider have the ability to deliver lethal bites to humans.

But even though aranea are supposedly so fearsome, many more people across the globe die from allergic reactions to insect stings than die from spider bites. Maybe the fear comes from the fact that spiders have eight eyes (mostly), eight legs and are able to shoot silk from their butts. How gross is that!

Sydney Funnel Web

Sydney Funnel Web

Sydney Funnel-web spider, Atrax robustus

This deadly, dark brown or black beauty hails from a region down-under near Sydney, Australia. According to some experts, it is the deadliest spider in the world, at least according to the number of human deaths it has caused. The funnel-web will grow to be a menacing 2 inches long.

Strangely enough, its venom is toxic only to humans and other primates. When injected into the body, the venom causes rapid firing of the nerve cells, which can lead to cell dysfunction and death. The venom does not affect other animals.

The Sydney funnel-web strings "triplines" around its burrow. When unsuspecting prey run into the tripline, the spider rushes out, grabs the prey, then takes it back to its burrow to munch on.

The funnel-web is a burrowing arachnid, which is usually only seen during mating season when the males leave their burrow looking for love. The funnel-web is more aggressive than other spiders, and its sharp fangs are capable of piercing an adult human or primate's fingernail. When threatened it will rear on its two hind legs and wave the other six legs ferociously.

This spider does not chase people or jump on them, though it does enter people's homes uninvited during mating season.

There have been no documented human fatalities since 1981, the year an anti-venom was developed.

This does not mean the spider is not dangerous, it is! If bitten, you should apply pressure to the wound and go to the hospital immediately. The doctors will determine if you need the anti-venom.

Brazilian Wandering spider. Phoneutria nigriventer

Brazilian Wandering spider. Phoneutria nigriventer

Brazilian Wandering Spider

Another aggressive arachnid, the Brazilian wandering spider, is found in South and Central America. Growing up to five inches long, the wandering spider spends the day sleeping under logs and rocks. It hunts at night, prowling the jungle floor for its next meal. When confronted it, like the funnel-web, will rear up on its back legs in a defensive posture.

The Brazilian wandering spider's venom is a neurotoxin that can cause paralysis of the muscles. If the bite victim is untreated, paralysis of the chest muscles and diaphragm can occur, leading to asphyxiation and death.

Scroll to Continue

One of the side effects of the venom in human males (and I would assume all male animals) who have been bitten is an hours long erection. Scientists have isolated the chemical responsible for this side effect and are studying it for its effectiveness in treating erectile dysfunction. Those scientists, always searching for ways to benefit mankind.

The Brazilian wandering spider, also known as the banana spider, was briefly named by the Guinness Book of World Records as the deadliest spider in the world. According to, of the 7,000 plus documented Brazilian bites, only 10 fatalities have been recorded. All of these known fatalities occurred before the development of an anti-venom.

The bite of the wandering spider is thought to be the most excruciatingly painful of all spider bites. If you are bitten, apply pressure to the bite and seek emergency medical treatment immediately.

A black widow the photographer found in his house

A black widow the photographer found in his house

Black Widow

Due to the distinctive red hourglass shape on its abdomen, the black widow is probably the most recognized and feared spider in North America. The name "black widow" came about because of the penchant of some of the females to kill the male after copulation. I'm sure a lot of ladies have felt that way after sex.

The widow family of spiders includes the brown widow and the red widow which are found across the globe.

Be aware that black widows may not have the hourglass pattern. Some females have red spots instead, and the male's pattern will usually be brown or yellow. The male is also much smaller than the female, making the amount of venom he can inject less harmful.

The black widow prefers dark crevices during the day, coming out at night to hunt. Many fatal black widow bites occurred in outhouses before the advent of modern plumbing. That's not a glamorous way to die.

The venom is a neurotoxin and symptoms of the bite usually occur within one hour.The initial bite is very painful. Later symptoms may be weakness, severe muscle cramps and weakness. The venom is usually only deadly to children or the elderly, but you should seek medical attention if whole body symptoms like shortness of breath occur.

The black widow mortality rate is said to be much less than <1%. An antivenom is also available for black widow venom.

An interesting note about black widows is that not all animals are affected equally by its bite. Cats and horses seem to suffer from the venom the most, dogs not as much. Rabbits and sheep seem to have no side-effects from the venom at all!

A redback spider (Latrodectus hasseltii) female, found in suburban Sydney.

A redback spider (Latrodectus hasseltii) female, found in suburban Sydney.

Australian Redback Spider

This close relative of the black widow is found in all parts of the continent of Australia. The female redback is much larger than the male. She is approximately a whopping 1 cm long, while the male is 3-4 mm long.

The female redback's body is pea-sized, and she has a red stripe on her back along with a red hourglass shape on her belly. The male is light brown, and the hourglass marking is usually pale and the dorsal (back) stripe is white.

The redback is a web builder, and its webs can be found in sheltered areas around sheds, rocks or logs. The redback's webs will be tangled and funnel-shaped.

Newly hatched redbacks will eat their hatched and unhatched brothers and sisters. There is a definite advantage to being the eldest sibling in this family! The females mature in about 4 months, while the males mature in three.

The redback is not aggressive and usually only attacks when its web is disturbed. Only the female is venomous, and with her small fang size she is not adept at piercing human flesh. Still, over 250 people a year are bitten in Australia and require antivenom. There have been no known fatalities in Australia for over 20 years thanks to the antivenom.

Brown recluse as compared to a U.S.A. penny

Brown recluse as compared to a U.S.A. penny

Brown Recluse Poll

The Brown Recluse

I have included the brown recluse just because of the fear surrounding this itsy-bitsy spider in recent years. Most scientists do not believe the bite is deadly, but a few others state that the tissue necrosis that results from a bite has led to human deaths.

Some doctors say that tissue ulcers and necrosis that is attributed to a recluse's venom is in fact a misdiagnosis, and may actually be the result of a staph infection. For one expert's opinion about whether the bite of a brown recluse causes tissue necrosis, click here.

The brown recluse, also known as the violin or fiddleback spider, is found in parts of the Midwest and southern American states. It will occasionally hitch a ride in someone's car or airline luggage and show up in unexpected places.

It makes a disorderly web in sheds, woodpiles, rotting logs, and sometimes in people's homes. A few homes have become heavily infested with the brown recluse and have had to be fumigated. That's one way to get rid of unwanted house guests.

The brown recluse's tiny fangs and reclusive nature make it unlikely to bite you. Most bites are attributed to the human directly coming into contact with the spider. People have been bitten when they have rolled onto the spider hiding among sheets or the person has come into contact with the recluse when reaching into dark places. Some people have been bitten when putting on clothing the recluse is hiding in.

If you are bitten by a brown recluse, wash the area immediately. Apply antibiotic cream, cover with a bandage, and watch for signs of infection. See a doctor immediately if you show signs of an allergic reaction.

Spider Books

What should you do if you are bitten by a spider?

If you are bitten by a spider, capture or kill it so it may be identified if you develop signs of envenomation. Wash the area, apply an antibiotic cream, and use an ice pack to control swelling.

If you suspect you have been bitten by a venomous spider, seek immediate medical treatment. Don't forget to take the spider (or its corpse) with you to the hospital!

Australian Spiders

  • Brown Recluse Spider - 5 Lies About the Brown Recluse Spider
    More lies are told about the brown recluse spider, Loxosceles reclusa, than any other arthropod in North America. Public hysteria about this shy spider has been fueled by media hype and medical misdiagnosis. It's time to set the record straight.


sandylue on October 21, 2019:

Interestingly, I have recently been told that 40% Zinc (like some diaper creams) will stop the necrosis of the recluse bite if applied within a few hours of the bite. I cannot vouch for this though...

Interesting article.

Gable Rhoads (author) from North Dakota on November 06, 2014:

I don't mind spiders RanaKm, but I wouldn't like any of these venomous ones in my house either! :)

RanaKm on November 05, 2014:

Geeeez,,,I hate spiders :( if I see ones as these in the pictures here I would most probably set the house on fire :D

Shaddie from Washington state on April 28, 2013:

Good hub!

Gable Rhoads (author) from North Dakota on March 09, 2013:

Thank you, Sheri. :)

Sheri Dusseault from Chemainus. BC, Canada on March 09, 2013:

Great information and good researching. Thanks!

Related Articles