Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth

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If you’re scared of spiders, then you have a very good reason to be. Not only are these alien-like creatures frightening with their hairy legs and multiple eyes, some of them are downright dangerous, capable of injecting venoms so toxic they’ll leave permanent injuries.

So which spiders are deadly? Which among the 40,000 species should you avoid at all cost? Here’s what you have to know about the 8 most wanted criminals in the spider universe.

Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth - black widow

Because of its ominous look, the American black widow is the poster child for deadly spiders.

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Why are some spiders deadly?

We know that spiders are dangerous. But why is that? Specifically, what can they do? Does a bite instantly kill you? Or is it something like disease-carrying mosquito bites that are slow, painful but curable?

Before we enumerate the arachnids that you should absolutely stay away from, let’s go back to the main reason that explains why spiders are deadly – their venom. There are two types, neurotoxic and necrotic.

Neurotoxic venoms are toxins that specifically target and destroy nerve tissue. Spiders mainly use this to paralyze their prey, so they’ll stop squirming during feeding time. Widow spiders, for example, have latrotoxins that cause muscles to contract. Other neurotoxic venoms trigger excessive sweating, nausea, vomiting, abdominal cramps, gooseflesh, and unstable blood pressure and fluid in the lungs.

Necrotic venom, on the other hand, is like something that we usually see in science fiction movies. In its most severe form, this toxin leads to necrosis, a condition where the cells and tissue are literally dying and inviting bacteria.

However, how serious a necrotic bite is depends mostly on the spider. There are some bites that only produce minor skin lesions while there are others that result into permanent damages in the body as well as systemic symptoms like nausea, kidney failure and in extreme cases, death.

So which spiders are deadly?

Now that you know the devastating effects of the most toxic spider venoms, here’s a closer look at the ones that have the deadliest reputations around the world.

Yellow Sac Spiders

Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth - Yellow Sac Spiders

Like what their name suggests, yellow sac spiders are known for their yellowish color. CC Image courtesy of Mad Max on Wikipedia

True to their name, Yellow Sac Spiders (Cheiracanthium) are a group of arachnids that have a tinge of yellow in their appearance. They’re also generally small, about 5 to 10 millimeters in size.

These spiders are capable of delivering a necrotizing venom called cytotoxin. They cause lesions that can escalate into permanently damaged cells and even disfigurement. However, their deadliness is something that’s debated by a lot of experts. A research published by The American Journal of Tropical Medicine and Hygiene even points out that a lot of their bites only cause mild necrosis while others are completely free from it. Whatever the case, a single bite from this spider should warrant a visit to the emergency immediately.

Black Widow Spiders

How to Get Rid of Spiders – DIY Methods to Keep Your House Spider-Free - Black Widow Spiders

Black widows contribute to a lot of spider bite cases in the US. CC Image courtesy of Shenrich91 on Wikipedia

Among all the widow spiders, the American Black Widows (Latrodectus mactans, Latrodectus hesperus, and Latrodectus variolus) are the most notorious.

These arachnids are famous of their shiny jet black bodies and their ominous blood-red marks on their abdomen, a mark that’s often shaped like an hourglass.

According to CBS News, a female black widow’s venom is thought to be 15 times more powerful than a rattlesnake’s. As we mentioned earlier, this spider has latrotoxin. That’s a powerful neurotoxin that causes latrodectism, a condition specifically triggered by widow spiders which results into vomiting, extreme pain, nausea, headaches and sweating among many other serious symptoms.

Contrary to popular belief, even though black widows are classified as deadly, they rarely kill anybody. In fact, among the 1,631 bite cases recorded by the American Association of Poison Control Centers’ National Poison Data System back in 2015, none of it involved death. But that doesn’t mean that you shouldn’t be careful around these spiders though.

These dangerous little creatures made into our most common biters list, check it out here.

The Katipo Spider

Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth - The Katipo Spider

A close relative of the black widow, the Katipo spider also injects roughly the same type of venom. CC Image courtesy of jesscostall on Wikipedia

Native to New Zealand, the Katipo Spider (Latrodectus katipo) is like the stylized version of the American widows. The female also has a shiny black body, but it has a lot of markings, ones that are bold, red and diamond-shaped. The marks are enclosed by thick white, yellow or cream-colored borders. And if you look at it closely, you’ll see brown and black stripes on its legs.

The katipo spider is endangered, but that doesn’t stop it from being one of New Zealand’s most venomous creatures. Bite cases are perpetrated by this arachnid even if it’s generally labeled as shy and non-aggressive. And if you do get bitten by it, you’ll get a dose of its latrotoxin. You’ll experience roughly the same painful symptoms that the American black widows give to their victims.

The Redback Spider

Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth - The Red Back Spider

Redbacks are the scourge of many homes in Australia. CC Image courtesy of Laurence Grayson on Flickr

Hands down, the widow family is definitely home to the deadliest creatures on the planet. That’s because the next spider in our list is another certified member. But this time, it’s from the land down under.

The Redback Spider or Latrodectus hasseltii is Australia’s black widow. It looks just like its American counterparts. However, its females have two types of patterns. The first is a longitudinal red mark on the abdomen, instead of an hourglass. The pattern doesn’t resemble anything, except an irregular and thick vertical slash. The second look is similar to the Katipo’s, but it’s got more banding, and there are more colors mixed in together.

Deaths from this spider are also very rare. In fact, CBS News reports that only 1/3 of its victims get injected with latrotoxin. But those who aren’t so lucky will suffer from vomiting, chest pain, irregular blood pressure among many other severe symptoms.

The Brown Recluse Spider

Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth - Brown Recluse

Even though they’re small, the brown recluse still manages to scare so many people. CC Image courtesy of Rosa Pineda on Wikipedia

A list of the deadliest spiders isn’t complete without the Loxosceles reclusa, the Brown Recluse Spider.

This little spider comes in an all-brown body. It has a distinct upside-down violin-shaped mark on its back, and it’s no bigger than a penny.

While the widow spiders are neurotoxic, the brown recluse is known for its necrotoxic bite. It’s a got a hemotoxin that specifically targets red blood cells and blood vessel walls which upsets the blood clotting process. And like all necrotoxins, it also causes cell degeneration, leaving permanent damages on the body.

The brown recluse is part of our common biters list. If you’d like to know what spiders have the most number of bite cases in the US, head to our post here.

Sicarius Spiders

Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth - Sicarius Spider

If you’re not careful, you might step on a Sicarius spider and suffer the painful consequences. CC Image courtesy of Beliar spider on Wikipedia

The genus Sicarius are known for looking like crabs. They also have a unique behavior of burying themselves to hide from predators and to catch prey. The most famous species is the Sicarius terrosus. It’s greyish brown, flat and only has 6 eyes.

Sicarius spiders are said to have the most potent venom ever recorded. Per drop, their necrotoxins are said to be more harmful than what the recluse spider has. They have sphingomyelinase D in them, a rare and devastating necrotic agent that targets skin cells, capable of producing open sores that can grow as large as 2.5 centimeters.

False Widow Spiders

Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth - False Widow Spider

False widows have more varied patterns and bands compared to widow spiders. CC Image courtesy of Martin Cooper on Flickr

Regardless of its name, this isn’t another Latrodectus spider. The False Widow Spider is actually another group of small arachnids called the Steatoda.

As for identifying them, false widows come in a lot of colors and patterns. Some of them even look like black widows, but almost all of them have bulbous round abdomens that are multiple times bigger than their cephalothorax.

When you’re bitten by a known venomous Steatoda, you’ll experience steatodism. It’s less severe compared to the latrodectism condition we mentioned above, but it’s no means less dangerous. You’ll still feel systemic symptoms like pain, lethargy and nausea for several hours.

Brazilian Wondering Spiders

Which Spiders Are Deadly? 8 of the Most Dangerous Spiders on Earth - Brazillian Wandering Spider

The Brazilian wandering spider lays its eggs on bananas. That’s one reason why it’s nicknamed the ‘Banana Spider’. CC Image courtesy of Techuser on Wikipedia

And lastly, we have the deadliest albeit the scariest arachnids in this group, the Brazilian Wandering Spiders, Banana Spiders or Phoneutria.

Don’t let the banana name fool you, these eight-legged creatures intimidate because of their size and toxicity. Normally, Brazilian wandering spiders can grow up to 5.1 to 5.9 inches. They’re fuzzy and have thick legs, so they look like flatter versions of tarantulas. Phoneutria cf. nigriventer, one of the more famous Brazilian wandering spiders, have a mocha brown body with black and cream stripes on its legs. It also has a pair of menacingly bright red mouthparts.

Frankly, there are only a handful of these arachnids that are dangerous to humans. But if you’re ever bitten by one of them, you’ll be injected by a potent neurotoxin called PhTx3. It messes with your body’s ion channels and causes paralysis, loss of muscle control, severe breathing problems and even bizarre reactions like forced erections that can lead to impotence (yes, you read that right). The venom also has been tested to contain chemicals that intensifies the feeling of pain. And with heavier amounts of the toxin, your heart and lungs will eventually stop working and give out.

Black widows

So that’s it! Brazilian wandering spiders, black widows, sicarius spiders and the other venomous eight-legged creatures we listed above – learning which spiders are deadly can basically save lives. So wherever you are in the world, try to be safe and get rid of the spiders living in your house right now. They could be one of the deadly ones!

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