What Is the Most Poisonous Spider in the World?

When you think of venomous spiders, the firsts to come to mind may be the Black Widow or the Redback Spider. After all, there are a lot of stories and even songs about those beautiful but deadly arachnids. But are these species the most venomous spiders to humans worldwide? We're here to tell you!

The record for the most poisonous spider to humans belongs to the Sydney Funnel-Web Spider. Only 0.2 mg of these species poison is enough to kill different primates, including adult persons! The venom attacks the nervous system and organs fast but, luckily, there's an antivenom.

But what are the symptoms of Funnel-Web Spider poisoning? Keep on reading to find out! We've also included a small list of other poisonous spiders that you should avoid.

What Is The Most Poisonous Spider In The World?
What Is The Most Poisonous Spider In The World?

The Three Most Poisonous Spider Species in the World

1. Sydney Funnel-Web Spider

There are 40 species of Funnel-Web Spiders, at least that we know of so far. And one of these spiders is the most venomous in the world.

The Sydney Funnel-Web spider has a poison that is especially lethal to all kinds of primates. Only 0.2mg/kg of these species venom is enough to kill an adult person! The early symptoms of Sydney Funnel-Web Spider poisoning include:

  • Nausea
  • Vomit
  • Drooling
  • Shortness of breath
  • Muscle twitching and spasms

And, as if the first symptoms weren’t scary enough, they appear in a matter of 10 to 30 minutes!

The venom of a Sydney Funnel-Web affects the nervous system and organs. So, if the person doesn't get treatment fast, the poison could lead to:

  • Hypotension
  • Circulatory issues
  • Pulmonary problems
  • Death

Luckily, there's an antivenom available, and deaths via a Funnel-Web's bite are now rare. That said, there is evidence of these spiders killing at least 13 people between 1927 to 1981. So, if a Funnel-Web Spider bites you, please seek medical attention right away. Getting treatment fast can save your life, for real!

And there's more! The venom of a Sydney Funnel-Web Spider is strangely not effective on other mammals. So, your dog or cat can survive an encounter with one of these spiders. But you will need medical attention and antivenom as soon as possible to stay alive.

The scientific name of this spider is Atrax Robustus, and, as you can imagine, it lives in Sydney. But you can also find these arachnids in other parts of New South Wales, in eastern Australia.

These spiders' natural habitat is in rainforests, but you can also spot them in gardens. A Funnel-Web Spider likes a humid and dark environment.

In these places, these species create their burrows in the shape of a funnel with silk. The spiders will bury themselves in these funnels that can be up to 60 centimeters deep. Then, their prey will fall into the web, and the arachnids will ambush it and kill it to feed on it.

Sydney Funnel-Web Spiders are carnivorous, and their diet includes:

  • Beetles
  • Cockroaches
  • Snails
  • Crickets
  • Lizards
  • Frogs

People sometimes mistake other spiders for Sydney Funnel-Webs. So, to identify these species, you need to look for a shiny, dark brown, or black carapace. This part of their bodies is so glossy that it almost looks like some sort of plastic.

The abdomen of a Sydney Funnel-Web spider is usually covered by reddish hairs as well.

Although they only get to be a maximum of 3.5cm big, these spiders have larger fangs than a King Brown Snake. Not only can these sharp fangs even break through the skin, but also nails AND toenails. Ouch!

A curious fact about these spiders is that the males are more poisonous than the females. This is an unusual behavior since female spiders tend to be more venomous than males in most species.

Another interesting part of Sydney Funnel-Web's behavior is that the males live alone. That said, the females prefer to live in colonies of up to 100 spiders.

2. Redback Spider

Everything You Need To Know About Redback Spiders As Pets
Everything You Need To Know About Redback Spiders As Pets

The Redback Spider is in the Black Widow family and is the second-most poisonous spider in the world. These species are native Australian, but you can also see them in New Zealand, Belgium, and Japan. 

Redback Spiders stand out for the striking, hourglass-shaped red mark on their backs. Hence the name. This mark is more noticeable on the females since they are one centimeter big, and the males are smaller.

But these spiders are as beautiful as they are lethal. The bite of a Redback Spider can cause:

  • Pain around the bite’s area
  • Redness and inflammation in the area
  • Nausea and vomit
  • Rapid heartbeats
  • Sweating
  • Inflammation of the lymph nodes

As with most spiders, children, old and sick people are more vulnerable to a Redback Spider's venom. But luckily, there's an antivenom available since 1956, and deaths aren't common anymore.

Also, despite their reputation, Redback Spiders are not aggressive towards humans. These arachnids are more likely to play dead or run away than to attack you. If one bites you, it may have felt threatened by you.

But, since Redback Spiders sometimes hide in people's houses, you may hurt one by accident. And, as you can imagine, the spider could end up biting you.

3. Red Widow Spider

The Red Widow Spider is also in the Black Widow family, and it stands out for, you guessed it, the red color of its legs. Also known as the Red-legged widow, this spider is around three centimeters big.

You can tell these species apart because their legs are entirely red or orange.  The abdomen of a Red Widow is black with red and orange spots or marks.

You can tell these species apart because their legs are entirely red or orange.  The abdomen of a Red Widow is black with red and orange spots or marks. Each of these spots has a yellow or white outline. These colors are nature's way to say: Back off, I'm poisonous!

The natural habitat of a Red Widow Spider is in Florida. But there are reports online of Red Widows expanding their territory around the US.

These spiders spin their webs in rosemary and palmetto shrubs. Red Widows wait for flying insects and other prey types to fall on their traps and then eat it. They also use their webs to secure their egg sacs after matting season.

As with other widow spiders, these species are famous and feared worldwide. But luckily for everyone, being bite one of these arachnids ain't as bad as you may have heard or read.

If a Red Widow Spider bites you, you'll experience the same symptoms of any widow's bite. And, as a result, you would have to go through the same treatment as well.

At first, you should wash the area where the spider bit you with water and soap. You should then apply ice to the wound and take an over-the-counter pain pill if you're a pain.

If other symptoms such as nausea, vomiting, or rapid heartbeat appear, see or call a doctor. Depending on how you react to the bite, doctors may prescribe:

  • Antibiotic lotions or ointment
  • Antibiotic pills, 
  • Pain medication
  • Pills to reduce the swellness
  • Antivenom

But, in most cases, you won't need more than pills for the pain and ice on the wound to overcome a Red Widow's bite.

Similarly, if you have a pet that was in contact with one of these spiders, the animal is likely to survive. Only smaller breeds of dogs and kittens are in real danger if a Red Widow bites them. Still, to prevent severe consequences, you should take your pet to the vet if you suspect a spider bit it.

Related Questions about Poisonous Spiders

Which Species of Poisonous Spiders Should I Avoid?

If you are confident than a spider's poisonous, you should avoid it altogether. Even if you know you'll survive a bite, there's going to be at least some pain, and there may be other complications. But, to help you out, here are the types of spiders you should avoid because they are venomous:

  • All spiders in the Black Widow family
  • Brown Recluse Spiders
  • Wolf Spiders

Oh, and if you see any spiders with bright red, orange, or yellow shades, you may want to keep your distance.

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