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What are the World's Deadliest Spiders?

By Kate Monteith
Updated May 21, 2024
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There are more than 50,000 known species of spider, but the world's deadliest spiders are few. All spiders can bite and inject venom, but their fangs are best suited for biting and stunning insects. When spiders do bite humans, they don’t always inject venom, and most bites cause no dangerous reaction.

When it comes to human fatalities, only a few arachnids may be classified as the world's deadliest spiders. Bites from black widow, brown recluse and Brazilian wandering spiders have been known to kill a small child or fragile adult now and then, but death by spider bite is not very common outside of deep jungle areas. A delay in medical attention often tips the scales in case of a fatal spider bite. Antivenin, when available, can be quite effective.

Identifying poisonous spiders can be difficult, but each has its own particular characteristics. Perhaps the most familiar is the black widow, an arachnid native to North America. They are very small, ranging from a half-inch to an inch (1.27 to 2.54 cm) in length, including legs. Black widows are completely black except for a large red or orange hourglass design on the underside of the abdomen. The trick is turning the spider over to inspect its belly. Black widow bites are seldom venomous, but symptoms of a poison bite include muscle cramps and pain at the wound site.

Another venomous North American spider is known as the brown recluse, sometimes called a fiddleback spider. It is usually brown or light brown with a mark looking somewhat like a violin faintly visible along its back. At less than an inch (2.54 cm) in length, the brown recluse often hides out in woodpiles and quiet corners of a basement or garage. Bites are rare, and necrosis of the bite wound is even rarer. A very small number of people can have a systemic reaction to a brown recluse bite. Fatalities are usually young children or people with weak immune systems.

The world's deadliest spiders to humans are Brazilian wandering spiders, also known as banana spiders. More people in the world die from their venom than any other poisonous spider on the globe. The Brazilian wandering spider is native to the jungles of South and Central America, and has a tendency to wander into populated areas, hence its name. Venomous banana spiders grow quite large, with a leg span reaching four to five inches (10.16 to 12.7 cm). When attacked, the spider will rear up on its hind legs and sway back and forth in an aggressive stance.

Tarantulas are often thought to be one of the world's deadliest spiders, but that is simply a myth. Tarantula spiders can grow to a huge size, with leg spans ranging between 3 and 12 inches (7.62 and 30.48 cm). They are also quite fat and hairy, giving the tarantula a fearsome appearance; however, tarantulas are relatively docile and rarely bite. Although no human has ever died directly from tarantula venom, a bite wound can become infected if not properly treated.

Lastly, the lowly insect known as a daddy long legs is definitely not one of the world's deadliest spiders. It’s not even really a spider. The daddy long legs has a set of tiny fangs that cannot bite through human skin. They do have claws on the end of their legs that can pinch, but daddy long legs are considered completely harmless.

Frequently Asked Questions

Which spider has the most potent venom?

The Brazilian wandering spider holds the title for the most potent venom, according to the Guinness World Records. Its neurotoxic venom can cause severe pain, inflammation, and, in extreme cases, paralysis or death if not treated promptly with antivenom.

How deadly is the bite of a Black Widow spider?

Black Widow spiders have a venom 15 times stronger than a rattlesnake's, according to National Geographic. However, fatalities are rare due to the small amount of venom injected. Symptoms include muscle aches and nausea, but with prompt medical treatment, the risk of death is significantly reduced.

Can a Brown Recluse spider's bite be fatal?

While a Brown Recluse spider's bite is venomous and can cause significant tissue damage, it is rarely fatal. According to the Centers for Disease Control and Prevention (CDC), death from a Brown Recluse bite is uncommon, and the elderly and children are most at risk.

What is the geographic range of the Funnel-Web spiders?

Australian Funnel-Web spiders, particularly the Sydney Funnel-Web, are found in Eastern Australia. They prefer moist, cool habitats and are often found in suburban areas, posing a risk to humans. Their venom can be lethal, but since the introduction of antivenom in 1981, there have been no recorded fatalities.

Are there any deadly spiders in Europe?

Europe is generally considered to have less dangerous spiders compared to other continents. However, the Mediterranean Black Widow, found in parts of Southern Europe, can deliver a medically significant bite. Its venom can cause latrodectism, a condition characterized by pain and muscle rigidity, but it is rarely life-threatening with proper medical care.

How can I identify a deadly spider?

Identifying a deadly spider involves recognizing specific markings and body shapes. For example, Black Widows are known for their shiny black color and red hourglass marking on the underside. Brown Recluses have a violin-shaped mark on their back. Always exercise caution and consult a professional for accurate identification.

AllThingsNature is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.

Discussion Comments

By dkarnowski — On Jul 11, 2010

We have both brown recluse and black widow spiders in my area of California. Luckily they do not show themselves often but the black widow webs are notorious for being strong and sticky. I often have to use a pressure washer to remove them from the eves of my house. There is nothing as unnerving as spring cleaning and flushing out the unwelcome guests from under the porch and in the garage.

By wesley91 — On Jul 11, 2010

@chrisinbama: Just a note: the meat tenderizer is also very helpful with jellyfish stings and insect bites. Be sure not to get the paste close to your eyes.

By chrisinbama — On Jul 11, 2010

@dill1971: Yes. The meat tenderizer actually works. It is certainly not for the serious spider bites, but is quite effective in the minor ones. The active ingredient in meat tenderizer, papain, has the capability to break down the protein in the venom of a spider bite.

Mix water and meat tenderizer and make a paste. Soak a couple of cotton balls in the paste for about two minutes. Make sure to wash the bite area well. Rub the bite area with one of the cotton balls. Cover with a loose bandage.

By Babalaas — On Jul 11, 2010

The Funnel web spider of Australia was the world’s deadliest spider until scientists developed funnel web anti-venom. The spiders are about the size of a big toe, and have huge fangs. The fangs are so long, sharp, and thick that they can pierce through shoes.

Funnel web spiders are also very aggressive, and will attack without provocation. What is most interesting is that the venom is only toxic to humans, apes, and monkeys.

If a funnel web bites you, you should seek the anti-venom immediately, or you may die. Besides the excruciating pain of the bites, the neurotoxin venom causes the victim to drool, twitch, seat, and tear. Basically, you become a real life zombie.

By dill1971 — On Jul 11, 2010

Does meat tenderizer really work in the treatment of a spider bite?

By cmsmith10 — On Jul 11, 2010

Please be aware that you will not always know when you have been bitten by a spider. I was bitten three years ago and had NO IDEA! My right leg started itching and I had been scratching it but there was no pain. It was red and swollen but I just thought it was an infected mosquito bite. After three days, I couldn’t walk. I had horrible discharge coming from my leg and the redness had spread almost to my foot.

After a trip to the ER and some tests, it was determined that I was bitten by a brown recluse. I had to have IV antibiotics and pretty strong pain medication. They had to cut the location of the bite and drain it.

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